[glamcem]

Originally Posted by TrackClub

Cem, i dont think it is the tire sizes at all. The fastest production car at the Ring has 255 fronts and the second fastest has 245 fronts. It is the car balance, which Randy Pobst suggested has to do with elsd. Given he's won Daytona 24 twice and is an accomplished pro otherwise, I'd take his musings over any amateur . Besides, with proper track alignment the C8 surprised him with too much oversteer not understeer. Noteworthy is also a fact that a C8 was only 1+ seconds slower vs GT500 on same tires at VIR. And while the Stang achieved it due to higher straght speeds, the C8 beat it in cornering.
To put it into perspective, the C8 would place 2nd on our fastest lap list, on measly 4S rubber against ZLE...
To your point, the C8 GS or Z06 may have slightly more rubber, but i dont think it will be much beyond 255 size. Because it is mid engine and any comparisons with C7 tire size wise are apples and oranges. Imo.

Tire and wheel size IS car balance though. I think you were referring to the Porsche GT cars (GT2 RS and GT3 RS), quick correction, they both come with 265/325 cheater Michelin Cup 2 R tires BTW and are rear engine cars so they require much wider rear tire even than those mid engine cars. Also they have steering in the rear and as Randy pointed out "they gain traction in corners they don't lose traction" . It would be apples to avocados because of that. I don't understand what his driver skill and experience has anything to do with any of this By adding more oversteer you're not actually fixing the underlying issue, you're simply lowering the car's overall limits, it's a "feel" thing. In order to fix the understeer, adding more grip (rubber) is the ideal solution. Most of the cars some with some sort of understeer from factory anyhow for general audience.

It's very early to speculate about the upcoming GS but I wouldn't be surprised if they put much wider tires up front. Of course on a front engine/heavy, RWD layout may benefit more from wider tires (up front) than a mid engine but that doesn't mean the C8 Z51 cannot. So far all that technology, DCT, mid engine, power is accounted for a slight performance bump ( 2 seconds) over previous car (C7 Z51) and C7 Z51 is much slower than a C7 GS in stock form. I also wouldn't use GT500 (700+hp muscle car) as a benchmark as Ford itself stated they're not interested in lap times. Yet it's still faster than a C8

[TrackClub]

Originally Posted by glamcem

Tire and wheel size IS car balance though. I think you were referring to the Porsche GT cars (GT2 RS and GT3 RS), quick correction, they both come with 265/325 cheater Michelin Cup 2 R tires BTW and are rear engine cars so they require much wider rear tire even than those mid engine cars. Also they have steering in the rear and as Randy pointed out "they gain traction in corners they don't lose traction" . It would be apples to avocados because of that. I don't understand what his driver skill and experience has anything to do with any of this By adding more oversteer you're not actually fixing the underlying issue, you're simply lowering the car's overall limits, it's a "feel" thing. In order to fix the understeer, adding more grip (rubber) is the ideal solution. Most of the cars some with some sort of understeer from factory anyhow for general audience.

It's very early to speculate about the upcoming GS but I wouldn't be surprised if they put much wider tires up front. Of course on a front engine/heavy, RWD layout may benefit more from wider tires (up front) than a mid engine but that doesn't mean the C8 Z51 cannot. So far all that technology, DCT, mid engine, power is accounted for a slight performance bump ( 2 seconds) over previous car (C7 Z51) and C7 Z51 is much slower than a C7 GS in stock form. I also wouldn't use GT500 (700+hp muscle car) as a benchmark as Ford itself stated they're not interested in lap times. Yet it's still faster than a C8

I stand corrected: GT2 RS indeed has 265/325 tires.
Tire size *can* relate to car balance, but many considerations have to be accounted for first, like engine layout weight distribution wise, suspension set up and by all means differential tuning! And that's why Randy mentioned the latter vs tire sizes. Why his experience as a pro driver has *anything* to do with this? Because as a pro racer, proper car tuning is crucial to him and he knows a thing or two about the subject no doubt whatsoever. And he didnt even mention tire sizes. If those were "ideal solution" i think he would have mentioned it
Changing camber on C8 didnt just "add oversteer" or "lowered the car's overall limit". To the contrary, the car went 3 seconds faster...How fast was faster? Look up 2min lap at VIR on 4S tires vs fastest laps sticky...
Now imagine what it could do on Cup2s...

Note that majority of race cars have highly tunable diff for a very good reason. At times, up to four of its components can often be adjusted individually: number of clutches, preload, drive and coast functions. Each making the car balance different depending on corner phase, driver inputs etc.
And Randy surely knows it. And that's likely why he suggested it.

Note the Carrera S (a car that a C8 is bench marked against) comes with 235/295 tires. GT3 with 245/305. The car that still officially holds a PRODUCTION (non modded) Ring record, Lambo SVJ comes with 255/355 tires. How's that for "balance"?

As to C8 being "only 2 seconds faster" than a C7: if i could go 2 seconds faster id be a friggin hero at the venues i run. I already pass many uber cars, including club racers on slicks, but extra 2 seconds would put me on a totally different orbit and on par with a completely different class of cars. Most importantly, that head to head test was done on street alignment the best i can tell. With track set up it could possibly be 5 seconds faster. At least that how i understand the comparos here.

As to Ford not caring about laptimes, i know this is their official corporate mantra, alas it is also a complete and utter BS. Why else would they upgrade GT350 to Cup2 tires as standard? To piss off ppl with higher replacement costs and poor longevity? No! To compete with 1le and have mags write about it. That's why.

Now about GT500 being a "muscle car"...dont know a single muscle car with full aero They clearly had a ZLE in their crosshairs as GT350R didnt quite cut it. Are you really not impressed that a measly C8 Z51 was only 1 second slower than the best that Ford can offer? Come on man

[glamcem]

Originally Posted by TrackClub

I stand corrected: GT2 RS indeed has 265/325 tires.
Tire size *can* relate to car balance, but many considerations have to be accounted for first, like engine layout weight distribution wise, suspension set up and by all means differential tuning! And that's why Randy mentioned the latter vs tire sizes. Why his experience as a pro driver has *anything* to do with this? Because as a pro racer, proper car tuning is crucial to him and he knows a thing or two about the subject no doubt whatsoever. And he didnt even mention tire sizes. If those were "ideal solution" i think he would have mentioned it
Changing camber on C8 didnt just "add oversteer" or "lowered the car's overall limit". To the contrary, the car went 3 seconds faster...How fast was faster? Look up 2min lap at VIR on 4S tires vs fastest laps sticky...
Now imagine what it could do on Cup2s...

Note that majority of race cars have highly tunable diff for a very good reason. At times, up to four of its components can often be adjusted individually: number of clutches, preload, drive and coast functions. Each making the car balance different depending on corner phase, driver inputs etc.
And Randy surely knows it. And that's likely why he suggested it.

Note the Carrera S (a car that a C8 is bench marked against) comes with 235/295 tires. GT3 with 245/305. The car that still officially holds a PRODUCTION (non modded) Ring record, Lambo SVJ comes with 255/355 tires. How's that for "balance"?

As to C8 being "only 2 seconds faster" than a C7: if i could go 2 seconds faster id be a friggin hero at the venues i run. I already pass many uber cars, including club racers on slicks, but extra 2 seconds would put me on a totally different orbit and on par with a completely different class of cars. Most importantly, that head to head test was done on street alignment the best i can tell. With track set up it could possibly be 5 seconds faster. At least that how i understand the comparos here.

As to Ford not caring about laptimes, i know this is their official corporate mantra, alas it is also a complete and utter BS. Why else would they upgrade GT350 to Cup2 tires as standard? To piss off ppl with higher replacement costs and poor longevity? No! To compete with 1le and have mags write about it. That's why.

Now about GT500 being a "muscle car"...dont know a single muscle car with full aero They clearly had a ZLE in their crosshairs as GT350R didnt quite cut it. Are you really not impressed that a measly C8 Z51 was only 1 second slower than the best that Ford can offer? Come on man

Well that would be an assumption As a pro racer his feedback is of course important but he has a crew to take car of the setup of the car (for him) based on his feedback. He wouldn't necessarily have to know about the details for each specific car..He wouldn't say things like "hey add more rubber, revise the MRC tuning" etc Like you said, the other things should be tuned to compensate those changes..like stiffer ARBs and/or, spring rates, different MRC or ABS tuning. That's where the GS or Z06 ( and their more aggressive Z07 variants) come in play, historically I mean. You may be right, they might not increase the front tire size about 40mm like they did previously but we just don't know yet, that would be another assumption. If the car understeers the easiest fix is to add more grip to the front so I wouldn't be surprised to see 285 or 295 wide tires up front, only time will tell.

For the sake of the staying on subject let's stick to C7 Z51 vs C8 Z51, because when we add other cars in the mix (Lambos, Porsche GT cars) they're much different cars and wouldn't tell us anything about the GM cars since like I said, Porsche also uses steering in the rear ..those cars and GM's cars couldn't be more different.

Btw, I think the reason why Ford clearly stated they're not interested in lap times (didn't announce official Ring lap times etc) is because they don't feel like they can compete with Corvettes or GM in general. To be able to tame that kind of power Cup 2 would be the bare minimum I think. So to answer your question, C8 is being 1 second slower than a GT 500 is not impressive for me because we already know the C7 GS can clearly beat both of them

Don't get me wrong I like everything I read about the C8 and I believe it has tons of potential but if all those crazy specs, better tires etc translate into only slightly better lap times than the C7 Z51 which is a car known with its poor track performance in OEM form, it'd make me think again. Who knows if the C8 GS is that good, I might consider getting one in the future too (just don't know if I would be happy without a manual and being underdog haha)

Speaking of tires, you know they used the old Michelin PSS tires on that C7 Z51 when they compared against the C8 Z51 with PS4S tires right? PS4S tires alone are 1.5-2 seconds quicker than the old PSS tires so I would really like to see back to back test with SS 1LE and C8 Z51, so far my money would go to C7 GS or SS 1LE for pure track performance.

[TrackClub]

Originally Posted by glamcem

Well that would be an assumption As a pro racer his feedback is of course important but he has a crew to take car of the setup of the car (for him) based on his feedback. He wouldn't necessarily have to know about the details for each specific car..He wouldn't say things like "hey add more rubber, revise the MRC tuning" etc Like you said, the other things should be tuned to compensate those changes..like stiffer ARBs and/or, spring rates, different MRC or ABS tuning. That's where the GS or Z06 ( and their more aggressive Z07 variants) come in play, historically I mean. You may be right, they might not increase the front tire size about 40mm like they did previously but we just don't know yet, that would be another assumption. If the car understeers the easiest fix is to add more grip to the front so I wouldn't be surprised to see 285 or 295 wide tires up front, only time will tell.

For the sake of the staying on subject let's stick to C7 Z51 vs C8 Z51, because when we add other cars in the mix (Lambos, Porsche GT cars) they're much different cars and wouldn't tell us anything about the GM cars since like I said, Porsche also uses steering in the rear ..those cars and GM's cars couldn't be more different.

Btw, I think the reason why Ford clearly stated they're not interested in lap times (didn't announce official Ring lap times etc) is because they don't feel like they can compete with Corvettes or GM in general. To be able to tame that kind of power Cup 2 would be the bare minimum I think. So to answer your question, C8 is being 1 second slower than a GT 500 is not impressive for me because we already know the C7 GS can clearly beat both of them

Don't get me wrong I like everything I read about the C8 and I believe it has tons of potential but if all those crazy specs, better tires etc translate into only slightly better lap times than the C7 Z51 which is a car known with its poor track performance in OEM form, it'd make me think again. Who knows if the C8 GS is that good, I might consider getting one in the future too (just don't know if I would be happy without a manual and being underdog haha)

Speaking of tires, you know they used the old Michelin PSS tires on that C7 Z51 when they compared against the C8 Z51 with PS4S tires right? PS4S tires alone are 1.5-2 seconds quicker than the old PSS tires so I would really like to see back to back test with SS 1LE and C8 Z51, so far my money would go to C7 GS or SS 1LE for pure track performance.

Completely agree with ya, that we got a whole bunch of assumptions here. But we do have some bona fide lap time data to at least draw some early conclusions. Ditto first hand feedback from a few sources, Randy being the best of them imo. To this point, do note that his comments about understeer are very minor by his own admission. And the car's behavior is different in slow vs fast corners. His BIGGEST issue is NOT understeer, but off throttle oversteer. Hence i dont believe tires play a role here and hence his specific comments about the diff calibration instead. Sure he has a crew at races, but he feels what the car is doing vs not. And any driver would have direct input of suggested changes during testing.
Anyway...his general feedback, even with existing small quirks is that a C8 is a much better BALANCED car vs a C7. Period.

So let's take a look at some laptimes: C7 GS is 2 secs faster at Laguna vs 1le, BUT that's a Z07 equipped car vs a standard version. OTOH a base C7 Z51 on old Michelins is only a fraction slower then a 1le. Hmmm...Then we have a 2min flat C8 z51 laptime at VIR that rival best recorded laps here of ZLEs on much better tires. That suggests incredible pace in my book.

We will have to wait till Randy drives the C8 at Laguna, but imo the car will eclipse the 1le laptimes by a large factor. There is ZERO chance, that a lighter, mid engine car, with more power will be slower than a 1le. Absolute zero! This also means it will rival GS Z06 performance. And defo beat a standard GS. Hands down.

C8 is by all means much closer to any 911, or exotic mid engine cars vs C7 because of its design. Rear wheel steering makes G2 RS special, but Lambo beats it nevertheless. So not at all apples to bananas. Slight design differences: sure, as no 2 cars are exactly the same and some tech will vary. But defo the same class of the car. And the C8 is in this class now much more so than any C7 ever was. But the C8 Z51 is a cheap version, so look at Carrera S as a proper comparison. When GM releases hi po versions, than we will be able to compare it to other uber models.

Armchair expert opinions are fun to dish out and apart from the VIR lap we dont have anything else reliable and will have to wait. But based on that posted time alone i think the C8 is a very stout performer. Here's a vid from a 2 time NASA champ driving one. And obviously he knows how to drive pretty good It is also interesting to see his specific comments. His message to my buddy who sent me the link was: "sell whatever you drive and get a C8" lol!

Cheers!

[TrackClub]

Oh, i should add a comment on PSS vs PS4 tires: not aware of the latter being 1.5 to 2 seconds faster.
The Tire Rack own tests scores them virtually identical re lap times and grip. If PS4 were that much faster they would be on my car a long time ago Kidding aside, the new compound is largely to increase longevity as far as i know and as such are a full class below ultra streets designed for track duty first and street second (re71r, rs4, cup2, g3, etc). And as such they are not even tested against these tires by Tire Rack and others.

[glamcem]

Originally Posted by TrackClub

Oh, i should add a comment on PSS vs PS4 tires: not aware of the latter being 1.5 to 2 seconds faster.
The Tire Rack own tests scores them virtually identical re lap times and grip. If PS4 were that much faster they would be on my car a long time ago Kidding aside, the new compound is largely to increase longevity as far as i know and as such are a full class below ultra streets designed for track duty first and street second (re71r, rs4, cup2, g3, etc). And as such they are not even tested against these tires by Tire Rack and others.

I remember reading this. According to MT, it's about 1.44 seconds faster in such a short track
https://www.motortrend.com/cars/bmw/...term-update-4/

[TrackClub]

Originally Posted by glamcem

I remember reading this. According to MT, it's about 1.44 seconds faster in such a short track
https://www.motortrend.com/cars/bmw/...term-update-4/

Good find Cem! It is likely they ran the original track test with used tires, while running the second track test with new rubber. Or it was colder. Or whatever. New to new tests has them neck to neck and PSS actually wins MT figure 8 test over 4S. Blah blah blah If 4S was really 1.4 secs faster on such a short track over PSS nobody would even look at RE71R, cup2 or RS4, or G3 for that matter.
That would make them extremely close to Cup2 performance. Good example is GS vs GS Z06 at Laguna.

I think we are bored stiff and look for something to "discuss" given our season is pretty much a write off
Cheers!

[glamcem]

hey don't jinx it sir! I just ordered a couple new front wheels and wanna try them on April 12th event (if not cancelled)

[TrackClub]

Originally Posted by glamcem

hey don't jinx it sir! I just ordered a couple new front wheels and wanna try them on April 12th event (if not cancelled)

Haha! Fingers crossed for ya, but play it super safe out there. Btw what set up did ya run the G3Rs on rim wise etc? And what rims did you order for your collection?
Cheers!

[TheRealJA105]

Originally Posted by glamcem

hey don't jinx it sir! I just ordered a couple new front wheels and wanna try them on April 12th event (if not cancelled)

MORE RIMS!!!!

BTW as far as you guys whole balance vs tire size debate in this thread. My opinion is that Chevy will and does need to increase the front tire size on track model C8s. I wouldn't say the tires are the chassis balance, I would say they are the easiest way to change the handling characteristics though.

[TrackClub]

Originally Posted by TheRealJA105

MORE RIMS!!!!

BTW as far as you guys whole balance vs tire size debate in this thread. My opinion is that Chevy will and does need to increase the front tire size on track model C8s. I wouldn't say the tires are the chassis balance, I would say they are the easiest way to change the handling characteristics though.

The C8 Z51 *is* a track version of a Corvette They will surely increase the tire sizes for future cars with more power though. Zero questions about that. But most likely F and R as in any mid/rear enginr car.

But, there are MUCH cheaper ways of influencing car's handling towards over or understeer vs tires alone, which is the most expensive consumable bar none, which cost is directly proportional to its size. And that was my point.
Here are some suggestions that will save a person tons of money over a long haul: simple spacers to change track width, rake change (if adjustable), different rate sways either F or R. Bottom line, in a properly balanced chassis, all components are calibrated to work together.

Of course as far as any manufacturer goes, they also have access to other excellent tools, such as diff calibration tuning, without having to invest money on anything else. Kinda when Randy gave GM his feedback on early 1le throttle response being too aggressive. And GM changed it in Track mode.

Looking at uber rear/mid engine cars, they all have tremendous size difference F vs R by design. And while hi po versions *may* offer bigger sizes, the stagger ratio is pretty much maintained. Meaning they increase BOTH F and R.

Time to start thinking according to different paradymes folks

McLaren Senna 245/315 (6 size stagger)
McLaren 600LT 225/285 (5)
Lambo Avantador 255/355 (9) ***
Ford GT 245/325 (7)
Audi R8 245/295 (4)
GT2 RS 265/325 (5)
GT3 245/305 (5)
Ferrari 488 Pista 245/305 (5)
718 Cayman GT4 245/295 (4)
C8 Z51 245/305 (5)

*** fastest, unmodified, production model at the Ring (on Trofeo Rs).

[glamcem]

Originally Posted by TrackClub

Haha! Fingers crossed for ya, but play it super safe out there. Btw what set up did ya run the G3Rs on rim wise etc? And what rims did you order for your collection?
Cheers!

I ordered 18x10.5" Apex SM-10 wheels (+22 offset) to be able to run 315 SQ setup. I really liked how the 19x11" SQ turned out and want to be able to compare them in both SQ sizes next time.

I shared more information on my build thread and didn't want to flood the other threads with my post so check out here for more info

https://www.camaro6.com/forums/showp...&postcount=322

Originally Posted by TheRealJA105

MORE RIMS!!!!

BTW as far as you guys whole balance vs tire size debate in this thread. My opinion is that Chevy will and does need to increase the front tire size on track model C8s. I wouldn't say the tires are the chassis balance, I would say they are the easiest way to change the handling characteristics though.

Agreed

I will soon list my 295/30/18 RR tires (two of them with one full session and two brand new ones) and two front wheels (Apex 18x10" also used for a one full session) if anyone is interested

[TrackClub]

Originally Posted by glamcem

I ordered 18x10.5" Apex SM-10 wheels (+22 offset) to be able to run 315 SQ setup. I really liked how the 19x11" SQ turned out and want to be able to compare them in both SQ sizes next time.

I shared more information on my build thread and didn't want to flood the other threads with my post so check out here for more info

https://www.camaro6.com/forums/showp...&postcount=322


Agreed

I will soon list my 295/30/18 RR tires (two of them with one full session and two brand new ones) and two front wheels (Apex 18x10" also used for a one full session) if anyone is interested

This will be one expensive experiment Cem
Thanks for reminding me about your build thread. Cheers!

[TheRealJA105]

Originally Posted by TrackClub

The C8 Z51 *is* a track version of a Corvette They will surely increase the tire sizes for future cars with more power though. Zero questions about that. But most likely F and R as in any mid/rear enginr car.

But, there are MUCH cheaper ways of influencing car's handling towards over or understeer vs tires alone, which is the most expensive consumable bar none, which cost is directly proportional to its size. And that was my point.
Here are some suggestions that will save a person tons of money over a long haul: simple spacers to change track width, rake change (if adjustable), different rate sways either F or R. Bottom line, in a properly balanced chassis, all components are calibrated to work together.

Of course as far as any manufacturer goes, they also have access to other excellent tools, such as diff calibration tuning, without having to invest money on anything else. Kinda when Randy gave GM his feedback on early 1le throttle response being too aggressive. And GM changed it in Track mode.

Looking at uber rear/mid engine cars, they all have tremendous size difference F vs R by design. And while hi po versions *may* offer bigger sizes, the stagger ratio is pretty much maintained. Meaning they increase BOTH F and R.

Time to start thinking according to different paradymes folks

McLaren Senna 245/315 (6 size stagger)
McLaren 600LT 225/285 (5)
Lambo Avantador 255/355 (9) ***
Ford GT 245/325 (7)
Audi R8 245/295 (4)
GT2 RS 265/325 (5)
GT3 245/305 (5)
Ferrari 488 Pista 245/305 (5)
718 Cayman GT4 245/295 (4)
C8 Z51 245/305 (5)

*** fastest, unmodified, production model at the Ring (on Trofeo Rs).

I get what you are saying, but I'll stick with tires being the easiest way to greatly affect handling. Also i'd wager to say tires are also the cheapest way for a Manufacturer to improve handling. They are only putting tires on once and don't really care about the consumable price. Compare the price difference in up sizing 2 front tires 20mm vs a couple hours in GM Engineering time and they are saving money immediately.