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CORVETTE TODAY #78-Corvette Test Driver, Jim Mero, Answers YOUR Questions!
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May 8, 2025
Famed Corvette Test Driver, Jim Mero, is back on the CORVETTE TODAY podcast with your host, Steve Garrett to answer YOUR questions! These were questions from CorvetteForum.com and MidEngineCorvetteForum.com. There are some great questions and outstanding responses from Jim. Jim talks about suspension and ride calibrations for the C6 and C7 Corvettes. He also talked about his experiences test on the Nurburgring and the Autobahn! It's a fascinating interview and episode of CORVETTE TODAY!
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0:00
[Music] welcome to corvette today the podcast
0:06
that talks about everything corvette with your host steve garrett mc and dj at one of the largest corvette weekends
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in the country corvette fun fest president of the corvette club of kansas city missouri and radio disc jockey at
0:19
the number one radio station in kansas city for over 40 years here's steve garrett
0:29
thanks for listening to corvette today the podcast that talks about everything corvette i'm your host steve garrett i
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first i'd like to thank our flagship sponsors of corvette today aerolary wheels a true forged wheel with over 20
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also mid-engine corvetteforum.com the forum that focuses on the new mid-engine c8 corvette meet a lot of
2:02
fellow corvette enthusiasts like yourself at mid-engine corvette forum.com also a shout out to
2:09
canadiancorvetforum.com welcoming corvette owners from around the world corvette test driver jim merrow is back
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on corvette today this time jim is answering your questions about america's favorite sports car jim it's great to
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have you back on the show and you are my first guest to appear three times on corvette today well i'll tell you what
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steve it's a complete honor let's hope the third time's a charm i'd like to first of all thank everybody
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who's not only listening but submitted questions i've seen them all i want to just tell you if i don't say it at each
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individual question they're all great and also over the next month or so i'll do my best to whatever questions we
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can't get to here i'll try to do a direct answer to you guys on the forum fantastic jim well let's get into
2:53
segment one our first question comes from yellowdreams and that's dreams with a z he's from corvetteform.com and it's
3:00
a two-part question he asks what are the biggest challenges that you had to overcome while developing the c7 zr1
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suspension and tuning it and if you could go back and change anything what would it be well when the c7 zr1 came up
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and that was introduced in one of the meetings i thought holy crap this is one of my dream cars what a way to wind up
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20 34 years at general motors i knew i was retiring nobody else did at the point so i thought this would be a great
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car to go out on the car had big arrow huge horsepower tons of cooling all those extra radiators the challenge was
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the mass of the car was a little higher than i really desired and the challenge was more making it drive like a light
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agile car the power to weight looked great but power to weight is really a straight-line effect our competitors are
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typically lighter weight than we are when you have a power rate ratio and a heavier car comparing it to a lighter
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car the lighter car wins every time because the fact that the power to weight is a straight line effect you
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have to corner you have to break the heavier cars so they're at a disadvantage every time the other thing
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that concerned me was putting 755 horsepower down to the rear tires and the cup two tires are awesome on the z06
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at that point i had no idea what adding another 100 horsepower would be like but we developed those tires back in 2013
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and this is a 2019 car i've said it before lee willards is a tired genius
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he's the best tire guy i've ever met and i've seen him do magic in a few months let alone six years having said
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that the first time we drove the car all that was put to ease because the car drove fine on the top two tires even
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though i know the car would have been significantly better with a newer tire at the same point i had just revised all
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my magnetic ride tuning philosophy on the c706 so it was a big revelation so i
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took all those learnings for the z06 and i basically arm-chaired calibration for
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the zr1 and as the cr1 progressed sort of the calibrations as the calibrations
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progressed the car just became more of a darling on the racetrack the thing is every time we went to a new track we
5:07
were putting down lap times that we didn't think we would ever achieve one of them was that vir a couple of us were
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running 150 ones on the full course i mean i remember back in the days when we were just trying to get the c6 zr1 under
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two minutes and it was just this car is going to be really good the second part of the question is if i could change
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anything what would it be based on what i said initially would have been absolutely new tires i did everything i
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could to convince a platform to go with new tires but there's a business case that i'm not responsible if i were
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responsible for it gm probably would have gone broke when i talk about those cup two tires i'll talk about what
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porsche's got going on they never considered a cup style tire until we did the cup two for the z06 i'll just
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digress to a funny story that happened at the nurburgring i was out in the c706
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and there was a porsche guy behind me i can't remember what he had but he was making at least as much power as i was
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maybe more the part of the track that it's probably 40 seconds in it's called quitterback hoe it's where the nissan
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went into the crowd and they decide to take the radius of that jump down so that was all under construction so we
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had to basically narrow you down to one lane he had to go 30 miles an hour so we're going up this cell 30 miles an
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hour then it opens up to a massive long straight away he was almost touching my bumper and it got to the point where he
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got a little better jump out of the construction zone than i did and he was back and forth and he clearly wanted to
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get around me but he couldn't go unless i signaled him to pass and i got to the next corner which was the turn going
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down into the foxhole for uh flute's rule and i just said let me get through this first turn and i'll never see the
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guy again and probably a minute later he was gone out of my mirrors now this is before they had the cup two hour tire so
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i finished the lap and the poorest guy i think he came in and there was a couple other cars sitting up at the paddock and
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mark royce and dan iman were there and i came in and the porsche guys were looking at our car which typically
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doesn't happen too often the paddock and i think it was royce just looked at the drivers and these weren't their
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development drivers either factory drivers and he said listen boys it's not just the tires
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so the reason i tell that story is because one year later guess what the
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porsche had the cup two hour tires and i guarantee you it was a direct result of what we were doing and i also know for
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sure that had we got a new tire it would have been better than the porsche yeah that's a kind of a long answer to a
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shorter question but i just wanted to kind of give that whole history of how things for the zr1 progress and how it
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actually affected the cr1 and the z06 affected what other companies did absolutely that's a great story too jim
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our next question comes from jack frost pdx from midengcorvetforum.com
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he says what do you think of msrc technology in general and how it has evolved at gm over time and the second
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part of the question is should we be adding it to our c8 corvette if we're not going to track the car okay i'll
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give you a little history in how the evolution of magnetic ride progressed when i first got introduced to it in the
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early 2000s it was a love-hate relationship i was having trouble with it i found a lot of flaws with it when i
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started doing my own shock dyno testing it's like here i am doing magnetic ride for my business and back then it was a
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battle i was fighting with delphi all the time and it got to the point where they were convinced that i was trying to
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get them off the car and another manufacturer in the car they thought i was in bed with a manufacturer because i
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was so adamant about getting them to fix these problems the other part of the frustration is out of all the people
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using it i was the only one complaining about it everybody else seemed happy but i'm like no they're experiencing the
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same problems as i am they just don't know it but over time delphi became open-minded
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and they said okay we'll start running our own tests lo and behold they thought the same results i did and boom full
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court press to their credit they put all hands on deck to correct these issues and i'm telling you they did the fixes
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they implemented were so good i wanted to change the way we used magnetic ride so up to the c6 zr1 only time we used
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magnetic ride was just an option on the base car it was just the fv1 with the passive dampers and magnetic rider was
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an option and the rest of the packages were on regular shocks i wanted to change the way we did that so with the
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c6 zr1 i said instead of taking a base car and trying to make some perceived
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handling even though the car did handle better it was more perceived than what i would like i wanted to take the hardcore
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track zr1 the c60r1 and use magnetic ride to make it ride better so you would
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get the best of both worlds and i was able to convince dave hill to let me take the car in that direction because
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it was a big step we had never done this before but all the electrical architecture for the zr1 had to be
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changed to include magnetic ride and he bought into it him and then later tom wallace you know came out to be a great
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car even though we've improved it since i was really happy with the way the car turned out it was shortly after that at
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c6 zr1 other motor companies were picking up magnetic ride bmw all the way
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up to an including ferrari so wow that was just a big transition and even since
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that c6 zr1 bwi is just continually to improve the product up to what's on the
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c8 better software better hardware better data but totally committed you know the rest is pretty much history
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right for the second part of the question let me put it this way i've been on record saying that in my mind no
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corvette should be sold without magnetic right yeah but i've also said i'm not in charge of the business case like i said
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before gm probably would have gone broke if i were but i know they have to keep the base price of that car as low as
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possible and relative to the track versus the street use of magnetic ride it's actually more beneficial on the
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street than it is on the track on the track it's huge but if you look at say a regular shock corvette that car
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has to be capable of driving up to 200 miles per hour driving exceptional up to
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200 miles per hour so if i have to make it drive exceptional 200 miles per hour that means that those kind of speeds i
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have to add a lot of damping well anything i do to make the car drive good at 200 miles an hour i own at 50 miles
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per hour so the car is totally compromised with magnetic ride everything i do at say 50 miles an hour
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or versus your daily driving i can scale all those damping factors for high speed
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so whatever i do to make the car drive good at up to 200 miles an hour doesn't affect anything i did at 50 miles per
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hour gotcha also magnetic ride has great handling algorithms so if you take a
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base car or a fe2 i can give the car more agility better steering response
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flatter cornering by just using the algorithms with magnetic ride but if you
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want those same attributes with a passive damper you got to put in higher spring rates bigger stabilizer bars
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increase the damping which will make the car just ride significantly worse amazing pretty cool pretty cool
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technology absolutely right buddy our next question comes from tella pierre from corvetteforum.com he says he'd like
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to know if you can share some corvette team thinking on the nurburgring record attempts and the reaction to competitors
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efforts we know by now the general motors approach is platform tuning first and fast lap is the second priority and
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then there's the second part of this question as well it would be interesting to discuss what happens if anything
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happens when you learn of a new record what happens after that well okay i'm gonna attack the second part of this
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question first from a corporate standpoint when somebody put out a lab time in an official capacity we never
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talked about it we didn't spend much time what can you do the nurburgring lab times our honor system right you just
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gotta assume that they ran it straight up like we do we had bigger fish to fry there was always new variants coming
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down the line it was pointless spending any time reflecting or considering doing anything about a competitor's laptop all
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we knew is we just needed to put our best car forward and let the results speak for themselves now having said
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that on a personal level a little different when i would see a laptime posted let me step back okay i love
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being an engineer i loved it since i was young but more than being an engineer i loved racing cars and honing my driving
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skills and anything track related whether it be what i was racing or on the corvette is very personal to me so
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clearly when somebody put out a lap time they made me go what i couldn't resist digging deeper into it you know i did
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this on my own time at home at night i would do my own little analysis and i've had some fairly decent tools without
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going into a lot of detail but when somebody would post their video because i heard a time when i needed the video
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then i could do my own analysis based on the video because i had the data for my
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cars and i would look at their entry speed their exit speed in a certain corner the corner duration acceleration
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to the break point of the next corner i'd use things like power to weight mass downforce aerodynamics and then i could
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come up with a pretty good idea if that lap time was legit because i could always refer back to the data that i had
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by then we had a lot of laps i knew all those things for my car and i could use the video to compare it to those car
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after i got the result i never took it to the company it was for my own satisfaction right gm wouldn't speak out
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because porsche did that to nissan probably 10 years ago it amounted to nothing now digress back to the first
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part of the question there was always a lot more effort in achieving lap times put forth by other companies
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we knew that and we knew what they put into it it just wasn't one of our priorities at least it wasn't our
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highest priority we didn't have the luxury of spending loads of time in germany the same single objective of
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laying down a lap time you know i know when the gtr was there i think they did their fast slide 709 they were there all
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summer long they were there for five months wow but we were there we would do our one or two trips and all we could do
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is make the car drive exceptional on the nurburgring and the autobahn and then a byproduct of making the car drive
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exceptional on the ring was a faster lap time so when comparing to what they do what we do the probably the best analogy
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i ever heard was i was at a corvette corral i think it was back shortly after around the c6 zr1 and taj was giving a
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speech to put things in their proper perspective he was comparing us to the gtr they posted a video he said there
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was probably 20 or 30 people over there supporting the gtr probably five six seven cars and he said in comparison we
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sent meryl mosher a technician and a six-pack that's awesome i never forgot that one
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that's great that's a great response from taj all right buddy our next question comes from john elegant from
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mid-engine corvette forum.com he asks what are the most rewarding specific track experiences you've had while
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testing corvette well that list is long the first time is not because of ultimate lap times when everything comes
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together when you're doing a new generation of a car there are so many disciplines that have to work in harmony
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and in the beginning these disciplines are all kind of doing their own thing things like powertrain powertrain
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cooling which those guys are awesome transmission algorithms the chassis tires elsd calibrations performance
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traction calibrations brakes and cooling aerodynamics you come out of the box and
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more than that the car didn't come out up to anyone's expectations and obviously the pressure and expectations
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were so high the pressure was immense and when you come out of the box and you're like oh my god this thing won't
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go through the turn or it's doing this or doing that i'll cite the c7 stingray first time we tested that on the track
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it was marginal at best it was a big disappointment but we had a huge dedicated team that's when you kind of
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go to work you start gelling and putting the combined disciplines together and when it all comes down and then two or
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three sessions later you go out and the car just makes this transformation it's
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completely euphoric you're like okay now everybody feels we're all progressing forward and we know this thing is going
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to be a rock star because even though it made the transition we have not started to refine it and all it's going to do is
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get better over time if i ever talk about my individual laps or lap times
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you know you and i have talked about we got a lot of nurburgring track experience we want to share in future podcasts
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so i'm just going to share probably one and people may not expect this the c7
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z06 to 710 but it was actually the time was the actual time we didn't achieve
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our objective of sub seven minute lap it was at 704 i did in the c7 zr1 and the
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reason for that is because i had to start the lap on cole tires for that one
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lap i had to go back and use every skill i'd learned over 33 years of racing
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corvette development just to get it around the track wow and i'm talking about a car i said it before was perfect
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an hour before and it was perfect the next morning but when you start on cold tires all bets are off yeah to properly
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warm the tires you need attractive force normal forces and i had to use slip angles and i'm telling you the slip
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angles were massive everybody doesn't know what a slip angle is it's the angle created from the direction of the tires
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to the direction of the car so say you come up to a turn the car's just got a ton of understeer so the car's going
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straight the tires are turned so that angle is what we call a slip angle and also the car would transition from
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understeer to oversteer so he'd finally get the car to turn in and then the back end would come around that lap was just
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me reacting to the car trying to do whatever i get to go through the corner even four minutes into the lap i almost
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wrecked the car several times wow even though it was a complete disappointment because it wasn't sub seven i thought as
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i was driving i'm thinking it's gonna be north of 715. so from a personal standpoint that was probably the last
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sure we'll probably never see but that was something that i was pretty happy with even though the circumstances were
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less than desirable for sure well jim our final question in segment one comes from rkc rlr and he's on
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midegencorvetforum.com he asks do you feel a difference between the fe1 and the fe-3 suspension when
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driving in a spirited manner that would still be considered safe and sane on the street and then the second part of this
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question is what about fe2 and fe4 suspension well there's a significant difference between fe1 and f3 the fe3
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needs to be track capable even though they're both passive damped that means the fp3 needs bigger bars more
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aggressive damping higher spring rates better tires so everything we do to make the fe3 exceptional on the track will
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directly result in a better kind of car for street driving when it comes to cornering the same thing goes for the
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comparison between the fa2 and the fe4 the progression between those two cars even though the fe1 and mp3 on pass the
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dam the fp2 and the mp4 magnetic ride that's the difference is the fe3 and the fb4 have to be track oriented
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all right well buddy let's take our first break and when we come back we'll answer more questions jim miro corvette
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state of kansas and now back to corvette today with your
21:53
host and my husband steve garrett [Music] hey thanks for listening to corvette
21:59
today the podcast that talks about everything corvette i'm your host steve garrett with me today is corvette test
22:05
driver jim marrow and jim is answering your questions on america's favorite sports car in segment number two we'll
22:11
start with bear06 jim he's from corvetteforum.com and he asks how
22:17
important is it to have rear caster set when getting an alignment the reason he asks is because he had a gm technician
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that said it's a waste of time well the gm tech was wrong like i'll compare it to the c7 magnetic ride upgrades the
22:30
dealers have been anything just north of disappointing and the same with setting the rear caster i've had a lot of people
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contact me on the forum and said the dealer won't set the rear caster and the rear caster is very important we
22:42
purposely made the c7s rear lower control arms adjustable both the front
22:48
and the rear in-board attachments so you can maintain zero caster when adjusting
22:53
camber the reason for that is the sixth generation car only had the rear attachment adjustable for increasing or
23:00
decreasing camber but when you adjust the camber on the c6 you add rear caster
23:05
because you're moving the rear attachment outboard which means the lower ball joint forward now when the
23:11
car goes into rebound or compression as well as roll the ball joints in the side of you are no longer linear lower ball
23:18
joint follows a different path in the upper ball joint and what that does is create a steer effect a steer effect in
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compression rebound and roll is very undesirable in the rear of the car so
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the c7 we said okay we want to maintain zero caster so you can adjust the both
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ends and then in the side view the ball joints remain linear when they go into compression and rebound and there's no
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steer effects at all the disappointing thing is it's not hard to monitor the rear caster when you're sitting the
23:44
camber there's a tool available all they do is put it on the knuckle and then they can adjust the front and the rear
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attachment the lower control arm and watch the faster gauge it's just an angle finder that's attached to the
23:55
knuckle and just make sure it stays at zero as you increase the camber so it's not hard to do and to my life i have no
24:02
idea why the dealers simply won't do it that's kind of crazy and it's very important it is very important it is our
24:09
next question comes from a person named mid engine and they're from mineenginecorvetform.com
24:14
we all know and greatly appreciate your track testing work for general motors was there other corvette development
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work that you did off the track oh absolutely first there was the same boring meetings and paperwork i had to
24:26
do that everybody else had to do however there was a lot of responsibility developing the car on the
24:32
street as much time as we worked developing the car on the track it was
24:37
incredibly important for me to develop it as good or better on the street i know that heritage of corvette is
24:43
racetrack bread and we put a lot of time and effort in making sure that no one's disappointed on the track but i really
24:50
take to heart to make sure that car is a good daily driver i would at the top of my head estimate for every hour i was on
24:57
the track i was probably 50 hours on the public roads wow it was very very important that guys can use the car not
25:04
only as a track car but it's a daily driver and i know most people don't track the car they're buying the car to
25:10
drive it every day and i can't disappoint him i want to make sure that this is a car that they're wanting to
25:15
walk out of the house and enjoy driving to and from work i wanted to make sure it was really good for that for tour and
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sport i would find the absolute worst roads in michigan which they're really bad here and i would spend just weeks
25:27
and weeks refining the calibrations to make sure that any kind of rough road the car would behave the way it should
25:33
and then i would also for every package go down to southeastern ohio and do mag
25:39
ride and steering for up to 12 hours a day for weeks at a time but i will say
25:45
probably one of my favorite things doing was doing all that but on the autobahn as much as i loved developing the car on
25:51
the racetrack there was nothing like spending a saturday or sunday 150 to 200
25:57
miles an hour doing mag ride and searing that's one of those things that i can't believe to let people do this so as much
26:03
as i love tuning the car on the track doing the ride work was okay but it was very important but man going down to
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southeastern ohio and the audubon were very close seconds absolutely almost makes me want to live in germany to just
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drive on the audubon every day oh i'm telling you the first time we did i just said i don't believe they let people do
26:21
this it was awesome that's amazing all right our next question comes from range 96 from corvetteform.com he says does
26:29
camber decrease when the suspension is compressed and if so why and what aftermarket suspension and or chassis
26:36
products do you recommend if any okay so first of all negative camber increases
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as the suspension goes into compression that's why the upper control arm is shorter than the lower control arm so in
26:47
the rear view the suspension goes into compression the upper control arm ball joint as a more aggressive curve than
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lower ball jointed increases camber so just the opposite the way you ask as far as the aftermarket products i never
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dabbled a lot in seeing what was out there when i was employed i was totally focused on production but after i
27:08
retired i did look i interacted with a few folks who purchased aftermarket stuff most of them the reason they
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contacted me were not satisfied with their purchase so i looked through a couple of these packages and i know a lot of these companies are selling
27:21
packages that i know were not developed to the extent that we did it was almost like a perceived thing you know tie it
27:28
down and it'll make the handles better right as a matter of fact shortly after i retired i was offered an opportunity
27:34
to endorse i think it was a bar of spring packages i can't remember who it was from but in good conscience i
27:39
refused to do it simply because if i didn't develop it or at least evaluated it i couldn't put my name on it that's
27:45
not to say that if somebody has a certain driving style and really really knows what they're doing they could
27:51
select certain aftermarket products to tailor the car to the way they drive say
27:57
they wanted less roll or more or less understeer you can buy bars that do that
28:02
the thing is you just got to be able to monitor some simple calculations of how much you're actually adding adding three
28:09
millimeters to a diameter of a staple is a huge change because the diameter torsional stiffness is to the fourth
28:15
power you want to make sure that you really know what you're doing and if you just want to take the car and increase
28:21
the roll stiffness maintaining the attitude or the understeer oversteer relationship then you want to make sure
28:27
you calculate the roll stiffness of the front bar to the rear bar and how much you're changing make sure the changes
28:33
are in the same magnitude we call the roll couple distribution or the entire lateral load transfer distribution
28:39
between the front and rear is maintained and that's very important gotcha all right our next question is from sk08
28:45
he's from midenginecorevetform.com and he asks will lowering the ride height of a corvette with msrc affect
28:52
the way the msrc operates are there any problems or concerns i'm glad he asked
28:58
that because i have lowered my c7 stingray on the stock bolts so this is
29:03
something i'm very interested in too and i'll speak everything up through c7 the dampers are very linear through zero so
29:10
lowering the car will have little if no effect on the dynamics the only concern would be ride height issues writing
29:17
curves and things like that so no up through c7 c6 and c7 you're fine lowering the car and maintaining the
29:23
drivability excellent all right and our last question in this section jim is from skank from corvickform.com he says
29:31
could you give an idea of what the ratio of segment timing versus actual time runs is he's assuming that it's
29:38
impossible to match a perfect theoretical segment timed lap versus one to a perfect hot lap that you ran what
29:44
percentages would there be if any okay so this is this might be a little longer answer because segment timing on the
29:50
nurburgring is so important segment time is the only way to get an idea of where
29:56
you would be on a timed lap if you look at the nurburgring there's probably in the neighborhood of 50 maybe 70 cars on
30:03
the track at the same time wow and when you're one of the fastest cars out there you're encountering traffic all the time
30:09
there's instruction going on you'll see two cars running together like in a lot of the videos that you can see they have
30:15
big l's on the rear window that means that's a learning or a training car there's suvs out there there's cars
30:21
running durability tests and the thing is you can't pass unless you're signaled to do so so you can come up on a car
30:29
until you see his turn signal go on and that would be the direction he's going to go and also the fact that he
30:34
acknowledges he sees you you can't pass them and there's some guys out there who would never pay attention and you'd run
30:39
through a minute minute of lap right on his tail he didn't know you were there i would go out on a warm-up lab to heat
30:44
the tires in any of the c7s or the c6s for us a warm-up lap would be about eight minutes and i would do the entire
30:51
lap and i wouldn't see another car i'm thinking oh my god got the track to myself especially if it was early in the
30:56
morning or right before the track closed you come to the start finish area you start the hot lap and within 30 seconds
31:02
you already encountering traffic just like a complete letdown so with all that traffic it's very hard to get an idea of
31:09
how fast you're running because you'll get segments oh i passed four or five cars and still pretty fast after you
31:14
come around 7 35 7 40. so you really have no idea how fast the car's going
31:20
and i'm not sure if any of the folks out there know who jeff moser is jeff's done several seminars at the bash he was our
31:27
analysis and simulation engineer he's a big boss now because he's so smart during the c6 years i don't want him
31:34
sitting behind a desk and just going through simulation programs i wanted him to come to the track with us we came up
31:40
with a program and treated our analysis engineers kind of like pratt miller did they were at the track with us all the
31:45
time compiling data you know actually we had jeff go with pratt miller to understand how they did it then when we
31:52
started going to the track when we downloaded data it took an hour hour and a half to analyze it all jeff wrote a
31:58
program i called the savior program to compile all our data analysis it was one download and it would break each of the
32:04
guys the thermal stuff the powertrain stuff the chassis stuff the simulation stuff those guys would have everything
32:10
they got in an hour and a half before in five minutes wow but part of the simulation program was segment timing
32:16
when we record data for development we use what's called an rt sensor an rt sensor is a military grade gps i think
32:24
it's accurate to within millimeters let's put it this way rt centers were used to guide ballistic missiles
32:30
so because of that we went to germany shipping those was a huge undertaking they took an act of god several weeks
32:36
and a bunch of paperwork to get them over there what jeff did is he broke the nurburgring into 42 segments each
32:42
segment had a either complete corner or a series of maybe two to three turns as
32:47
part of the segment and it's important to make sure you do complete turns because say you take a turn and break it
32:53
into a segment is corner entry to apex and the next segment is apex to corner exit well you can come into that corner
33:00
super hot get it to the apex and then blow the exit and then the next lap come in fairly slow but get a good shot out
33:08
and you would get that second segment then you would have a segment time that's unrealistic that you could never
33:13
do because you can't drive a corner from corner entry to corner exits like those two segments jeff really put a lot of
33:19
thought into it and as we were accumulating laps during our industry pool testing we would then start getting
33:25
an idea of what we could do on a single lap and the way it worked is when we downloaded data i would get the file i
33:32
would put into an analysis program and then it would spit out a table of these 42 segments that i just did in that
33:39
session it would be two three four five laps i would get a time for each of the 42 segments and it would put that table
33:46
into a bigger table with all the previous sessions i had run up to that time wow then then it would color code
33:53
the segment times green and red so over a week or two when you're getting up to
33:58
30 laps that segment sheet became very large the beauty of the color coding was you can immediately look and see okay
34:05
this was a fast segment this was a fast segment so it would compare everything you had run 30 40 laps it would just so
34:10
here's the fastest segment and then it would take all those green segments combine them and that's where you would
34:15
get your theoretical lab that's how we utilize the segment table now when we talk about matching the segment times or
34:22
time becoming unattainable there's certain truth to that let me kind of explain that so when you're doing all
34:28
your development then it's fast lap time i'm not sure where it comes from but you suddenly go to a different place
34:34
mentally you know when you take that first turn and the stopwatch is on and you think oh it may be like any other
34:40
lap it's not it's completely different everything changes you have to be very disciplined it's like running a 13-mile
34:47
qualifying lab you got to stay in the moment you can't think about developing and your mind has been processing your
34:53
development for what two weeks at that point well you gotta step away from that and go into you're no longer thinking
34:59
about development you can't get ahead of yourself and that's easy to do you got to stay in the moment absolutely and somehow the
35:07
speed and the time just happened just because you're being more disciplined and also when you're driving during
35:12
industry pool you're not thinking about anything that remembers almost a fast lap because you know you're not going to get it because
35:18
of all the traffic so i think subconsciously you become a little complacent and not going to that place
35:24
you do when you know you are going for time also when you're developing a car you have to drive consistent consistency
35:31
is the most important thing when you're a being changes so you got to drive 95 to 98 percent every single lap and doing
35:38
it for up to 150 turns so you can make sure you get a good feel for what your
35:44
changes are and if it makes the car drive better when you're in development mode you're thinking about changes
35:49
you're driving the car and all you're thinking about is processing what the car is doing and what what your next
35:54
change is going to be you're doing all that while you're driving so then you spend all this time up to two weeks doing that then it's fast lap time the
36:01
track is completely yours only objective is speed and time then you go into race mode digressing back to when i said i
36:08
historically beat the segments those are the segments that i obtained during two weeks of industry pool
36:14
throughout traffic and things like that the longer we drive that segment time tends to flatten out or the improvements
36:21
in it i mean we'll go out for a tank of fuel and i'll come in and start running the numbers we would be elated if we
36:28
picked up a few tenths of a second or dropped that theoretical lab a few tenths of a second but when i finished a
36:34
fast lap say for the c7 c06 i had two one lap sessions at the end of the day for fast slam so after i do a fast slap
36:41
if i put that data into the segment table the time decreases by two or three seconds wow so then when you start
36:48
including fast slaps into the segment table that's when the time becomes unattainable because now you're getting
36:55
closer to have to drive to complete perfection i said it before if you ask
37:00
any race car driver if they've ever driven a perfect lamp the answer is always going to be no if you could drive
37:05
to perfection how fast the power will be for instance i'll say i think our segment time for the c706 was like a 713
37:14
of all the industry pool data that we got after i ran those two fast laps it went down like 707 the car is capable of
37:21
a 707 maybe a 706 you got to be perfect absolutely right well buddy let's take our final break when we come back in
37:27
segment three we'll finish up our questions asked by you with jim marrow corvette test driver on corvette today
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38:36
this is the corvette today podcast with steve garrett hey thanks for listening to corvette
38:43
today the podcast that talks about everything corvette i'm your host steve garrett with me is fame corvette test
38:49
driver jim miro and jim's answering your questions about america's favorite sports car jim in this final segment
38:55
we'll start with irv bulldogs 72 he's from corvette forum and he asked if you
39:01
had fewer mandates and budget constraints on the c7 chassis development was it still locked in the
39:06
c7 suspension what would you have done differently and also did gm ever test a
39:11
fixed roof on the c7 well the first part of that question is easy there'd be three things i would have changed first
39:17
is tires second is tires the third would have been tires
39:22
i spoke in one of the earlier segments answering a question about the development of cup two tires and how
39:27
much better they would have been if we did a zr1 tire anybody knows me knows that tires or anything probably the
39:33
second thing i would have done is maybe had more adjustability in the rear wing obviously for safety the thought was to
39:40
do two positions a street position in the track position right the track position was determined by we had a
39:46
bunch of our high performance drivers all of them had different driving styles and that's one of the tough things to do
39:51
when you do a track oriented car is when you're tuning for the masses you got to somehow accommodate a bunch of different
39:56
driving styles so the wing settings were very conservative we had it higher for
40:01
more rear downforce for my personal driving i would have liked to lower the wing because i like the car a bit more
40:07
freer than most of the people do but that's just not a good thing to do for the masses you want to deviate to the
40:13
side of understeer relative to the second part of the question is like you said i'm one of those people who never
40:18
took the roof off the car over 15 years on the corvette i might have put the convertible top down one time
40:24
and i never took a roof off the car i will say i don't think we ever thought about or talked about a fixed roof on
40:30
the c7 the objective for the seventh generation car with the top off was to have the same structural rigidity as a
40:37
c6 with the roof bolted on so the c7 structure is very very robust i don't
40:43
know what the first standing and first torch numbers would have been for the c7 if you had bolted the roof end as
40:49
opposed to clamped it on and also i don't know if there's anything aftermarket out there relative to
40:54
bolting in a c7 roof our next question jim comes from max powers from mid-engine corvetteform.com he says i
41:01
understand the benefits of transverse composite leaf springs but if they're so good why don't other cars use them that's a
41:08
good question sure is when you look at from a tire patch perspective the tire patch doesn't care what kind of spring
41:15
damper system is on the car it just needs them both to work together and there are benefits to the composite leaf
41:21
they're very light and they do add roll stiffness however there's a lot of engineering drawbacks to the closet leaf
41:27
when you compare it to a coil spring first of all they're very big they take up a lot of room where other things
41:32
could potentially be packaged they're very expensive so the tuning library is very limited because it just
41:39
costs a fortune to prototype those springs so we were limited on what we could get for tuning say you got your
41:45
original library and you wanted another rate it took weeks maybe a month maybe longer for them to prototype the spring
41:52
so you get it so you all have down time changing them is a pain in the butt changing uh coil spring takes a fraction
41:58
of the time you can do it in minutes and when you're at the racetrack that time is precious and also that time is money
42:06
also with coil springs you can maintain your ride height and cross weights by taking a few measurements before you
42:12
remove the spring and resetting it after you install the new spring where if you do a leaf spring at the track you got to
42:18
go back to ground zero and do the complete alignment over yeah and the other thing is adjusting for ride
42:23
heights and cross weights the leaf spring is a pain because you got to get under the car you have to be able to use
42:29
this special tool to lift the spring off the control arm make your adjustment then you got to roll the car out make
42:36
sure the puck is not binding up on the control arm so basically the move to call springs on the ca was a really good
42:42
piece of business yeah probably was for sure jim our next question is from ao zora on corvetteforum.com
42:49
and he asks i know that you've touched on this recently but in your opinion well the c806 with a z07 trim and the
42:56
cup 2 r tires make a sub 7 nurburgring time will it make sub 7 well that
43:02
remains to be seen based on my answer on the corvette forum that kind of took on a life of its own that i wasn't
43:08
expecting i think it should i'll give you some of my rationale that was off the top of my head i called my arm chair
43:14
simulation and i'm pretty comfortable with it and in the past my arm chair simulation was actually some closer than
43:19
some of our objective simulations my thought process during the answer of that question on the forum was first of
43:25
all i compared it to my c7 710 at first it was just because 06 to z06
43:32
but also my c7 c06 time was actual bonafide time warm-up lab everything
43:38
worked as it should have right i didn't use the zr1 because i have no idea how fast i would have gone given a warm-up
43:45
lap on a clear track so i just wanted to make sure that i was comparing it to something that we actually did right
43:51
back to my armchair analysis it's clear by now that i'm all about tires now when i compared the cup one to the cup two
43:58
tires i believe i think we got about a two second elap time improvement on the
44:04
cup one then if i consider the cup twos to the cup two r's for us it could have been
44:10
maybe a cup two r plus that would have been another significant reduction in time so then you think about the dct the
44:17
710 that i ran was in a manual so i basically used second through fifth gear dct has way more gears available to keep
44:24
the engine its power band the dct shifts are lightning quick much faster than the
44:29
manual and i said it before i have no idea what the ch06's horsepower is going
44:34
to come in at i find it hard to believe that it'll be less than a c7 z06 so i think there'll be a horsepower advantage
44:41
i think about performance traction management like magneride every generation ptm gets better and better
44:47
having said that i chose not to run ptn and the c706 at the nurburgring so i had
44:52
everything off except for abs and that's because in the corners at the nurburgring where ptm really worked well
44:59
i could drive just as fast or without it however on the nurburgring there were some corners where ptm just pulled the
45:05
car down a little too much and what i liked and in those counters data showed that i was faster without it so i ran
45:11
without it but having said that i would never recommend any owner run without it it is a good system unless you're at the
45:18
top of your game you really want it on if you look at it from the c6 through the c7 if the improvements for ptm
45:24
continue through ca believe me i'm sure it'd be a technology even i would have embraced so summing it all up i think i
45:30
said 12 to 14 seconds and i think that's doable i'll also put a caveat in that i've never driven a c8 i don't know the
45:36
dynamics to the car but i see no reason why it shouldn't be stellar just a little sidebar ears there was a
45:42
photograph that the person looked like me in the passenger seat and i've been asked by a bunch of people was i at the
45:48
nurburgring for any of that ca testing and the answer is no that photo was just another super good looking dude
45:55
absolutely right buddy all right our next question comes from little cuda from mid-engine corvette forum.com and
46:01
he asks are all c6 magnetic ride shocks interchangeable and are the different characteristics based on the application
46:08
like grand sport versus z06 versus zr1 yeah so i've got to go by memory on this
46:14
one but when it comes to just the piston and the shock which is everything there were two different shocks the fe2 or
46:20
base with magnetic ride the grand sport the z06 without z07 427 convertible and
46:27
the zr1 and the z06 with z07 without cup tires all the same shock the z06 with
46:34
z07 and the zr1 with top tires had a different shock or piston and the differences between those two
46:42
were fairly mild changes made in the piston just to add more hydraulic damping at very low shock velocities now
46:49
there might have been some mild changes based on the way we trim the cars for compression and rebound travel i think
46:56
those were only a few millimeters in either direction so i really can't remember specifics on that gotcha that's
47:02
okay our next question comes from mark yvette from corvetteforum.com and he
47:07
asks what would you recommend for suspension on a c6 grand sport without msrc that sees track use on an advanced
47:16
slash instructor level but is mostly a street car and he says note they likely had to compromise more for the street
47:23
for the grand sport but if you were to compromise more for the track what would you change okay so first let me start by
47:30
saying i believe the c6 transport with passive dampers was only combined with
47:36
an automatic and a convertible that car was never intended to see a race track and that's why that car did not have a
47:42
dry sump boiling system they were all wet sumps i remember back when we were doing the c6 gram sport tom wallace
47:50
there was a chief engineer at the time he said we will never put a dry sump in any grand sport so we tested it and we
47:56
tested with a wet sump and we could never get adequate oil pressure on the race track now finally you know it was
48:01
like we were getting really worried and finally we were hitting our drop dead date if we ever wanted to think about implementing a dry sum system we were in
48:08
that final meeting and tom's sitting at the back of the room and he just starts laughing and we're like what are you laughing about because i knew i just
48:14
want to put you guys back against the wall you convinced me that the car needs to dry some you're going to get to dry
48:19
some wow so the reason i digress back in that piece of history is i remember back
48:24
testing with the wet stump and so my first recommendation would be if you're going to go hardcore track you need to
48:31
find an aftermarket dry sump system to put on the car at that point now you can make the car more capable i would
48:37
probably go with different shocks something that's adjustable i would assume that you're not going to run
48:42
anything that comes close to those old goodyear f1 supercar tires because those things were marginal on the track at
48:48
best so i would then assume you're going to go with a tire with a lot more grip then you're going to want to start
48:53
looking at higher spring rates increase roll stiffness by stabilizer bars tune it basically to your driving style
48:59
gotcha yeah that makes sense for sure jim our final question is from mid-year roadster on corvetteforum.com he says
49:07
can you really tune the suspension to give a smoother ride on a c6 absolutely
49:12
the history of how we how the magnetic ride calibrations progressed from c5 to
49:17
c6 the c7 is very well documented back in the 2000s magnetic ride was really new technology we were just cutting our
49:24
teeth with tuning philosophies understanding the authority of the system even though we've improved that
49:29
we really were satisfied and felt we did a good job with the cars but over 10 to 12 years you get more experience with
49:36
the software you've got a bunch more bench test data from the supplier helps you understand the relationship between
49:42
mechanical and the electrical attributes of the system and all that led up to a total complete major change in tuning
49:49
philosophies and strategies with the 2019 seventh generation cars basically
49:55
just taking those philosophies and implementing them into the sixth generation power the improvements in the sixth generation car are as good as
50:02
we're better than what we saw in the seventh generation that's a good question and a great answer too buddy thanks thank you jim
50:08
before we go let's talk about your business and what you do because you travel all over the country tuning cars
50:13
and that's really a cool deal you got a trip coming up as a matter of fact yeah as i just stated in that last question i
50:19
wanted to be able to get the sixth generation cars the same level or better improvement to the seventh generation
50:25
car so after i retired i said what the hell give it a try and i did it came out really good so now if you have a 2009 or
50:33
a 2013 corvette with magnetic ride we can either directly program the car or
50:38
send you a module with the new programming in it everything comes with 100 money back guarantee we've done over
50:45
400 cars and we're still lucky to be at 100 satisfaction contact me on my
50:50
website jmerrell.com there you go and you can write to jim at jim jim marrow.com and like jim said earlier in
50:57
the podcast he's going to get back to the corvette forum.com questions as well as the mid-engine corvette forum.com
51:04
questions and answer those so if you do have some other questions you can ask them right through those two websites
51:09
just give me a month or two to do that because we're getting ready for this big trip it's gonna take three weeks so i will get to them though i promise that
51:16
sounds great jim thanks so much for being on corvette today again we appreciate your time and answering all
51:22
these questions and congratulations and continued success it's been an honor steve i'm just over the top humbled by
51:28
the fact that this is my third time doing this buddy i love having you on the show we'll have to do it again soon
51:34
thanks for listening to corvette today and please be sure to tell your family friends and other corvette enthusiasts
51:39
about the corvette today podcast and also thanks to our flagship sponsors american hydrocarbon at
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you've been listening to corvette today with steve garrett if you'd like to contact steve with any thoughts on the
52:12
podcast or ideas for guests on corvette today you can email him at steve stevegarrettdj gmail.com
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that's stevegarrettdj gmail.com garrett has two r's and two t's or
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thanks again for listening to corvette today
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you
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