sam90lx

I think that's where Ox hangs out! With his Zaino.

OnPoint

Sin City

"Same" (notice the quotation marks) transmission with a different engine and program mapping is a different powertrain.

Big Dan 427

And not one of those cars has the LS or Ring or numerous other track records! Are they good handling applications for those particular cars, maybe but then why do the cars with the biggest foot print own all the records! You have all the answers so let's hear it or are you too busy eating those turds in your cereal?

Trackaholic

There was a post earlier that had the GM "authorized" explanation as to why. It makes sense from an engineering standpoint.

With the C7 GM is going for a more refined car. This means that the improved steering feel, reduced road noise, and improved economy are all important aspects of the car's design. If they can achieve the performance goals with a small tire, while improving those other aspects in part due to that smaller tire, then it is a win-win for the team.

Some other aspects to consider:
1. What do you think determines the tire's contact area? The answer is car weight/balance and tire pressure. So, just throwing in fatter tires won't necessarily improve the contact patch unless you change one of those other two aspects, which can impact performance in other ways.

2. Because the C7 is heavier, and has a more rearward weight bias, it has the potential to have a larger contact patch than any of the C6 cars (depending of course on tire pressure).

3. Does anyone know enough about any of these tire compounds to know if they are optimized for certian contact pressures? Do we know what the recommended tire pressures are for the C7 yet? It may be that the new compounds work better at higher contact pressures, and therefore a smaller contact patch is beneficial.

Anyhow, I don't know the answers to much of the questions, only that there is a fine balance between tire size, pressure, overall balance, steering feel, etc. It isn't always about sticking on a fatter tire unless you also change other aspects. Changing those other aspects can have a negative affect on other areas of performance.

Of course visually it is pretty badass to have massive rear tires. I fully expect the higher performance versions to run a wider rear tire with a lower pressure. Less sure about the fronts. I guess it sounds like the hi-po version will be supercharged, so that would mean added weight on the front, which would probably mean a wider tire up front as well.

-T

mo-shy

Guibo

Perhaps not all of those manufacturers care so much about track times. A lot of those cars are better roadcars than something as extreme as an ACR or the Gumpert (which is about as relevant to road driving as a Group C racecar). Some of those cars don't even break the 450 hp mark let alone 600. While the 'Ring does stress suspension and tires like few other tracks, it's still also a very fast track with some of the fastest average speeds around. Cars with very mediocre setups can still lap pretty fast there; the Koenigsegg, for example, sets a fast lap not because it handles exceptionally well, but because it makes mincemeat of the straights (800+ hp tends to do that).
Veyron has among the fattest tires for any stock production car at 365mm, yet it's not the fastest on tracks.

All valid points IMO. With regard to the Pilot Super Sport, it is not just the compound, but also the construction of the carcass. It is designed to withstand high pressures and temps far better than other tires, thus maintaining a flatter profile against the road/track.



Before anyone says the tire on the right is far wider, it's not. Treadblocks for both tires measured at the same points are roughly equal. It would take a much, much wider tire on the left to match the contact patch of the one on the right (and think what kind of unsprung mass would be involved just to match it). Like other Michelin tires, the PSS is multi-compound too, but it has a higher treadwear rating than the old PS2. Perhaps this is because by maintaining a more uniform shape, it doesn't need as soft a compound to outperform the old-style tire, nor does it need to be wider.

ck9887

So what they are saying is they chose a narrower wheel/tire combo based on the performance results they could achieve with one specific tire?

So what about after the first 20K miles when it's time for new rubber and the majority of owners don't go with the factory tire?

JustinStrife

How do you know the majority won't stay with the OEM tires?

Snorman

On my '12 GT-R, I decided to go with a set of HRE's. I did a big tire size upgrade to a 285/335 setup in a Michelin PSS (from the factory RFs). I honestly don't like the way the car feels on the PSS's. The bigger tire has more sidewall flex and doesn't feel as planted as the factory RFs. It looks better, and it may have some absolute performance benefits, but I liked the feel of the factory tire/wheel setup better.
OEM's put a lot of development time and testing into the suspension and tires, swapping out to a bigger tire just for looks or even for a perceived performance benefit isn't always a wise idea.
S.

JoesC5

Didn't you go from a fun flat tire to a non run flat tire? That could explain the differences in sidewall flexing. You made two changes(size and tire construction) yet you selected size as the reason for the difference you feel in the tire's performance. What made you think that size and not tire construction was the culprit?

sam90lx

Yes, runflats are a stiffer tire.

RedLS6

Just what Michelin has put out in their press releases; pasted as follows: It sounds like Michelin used FEA to design the dynamic contact patch shape under cornering stress.


**************************************** ********************************

•Footprint shape designed by sophisticated computer modeling and analytic tools traditionally used to predict the stresses occurring in racing tires. This is the first time these tools have been used to achieve higher performance in a street tire.
•A new, advanced Aramid cap ply specially tuned for optimum contact patch control for high speed and high performance tire handling and wear life.
•A new specially adapted internal rubber compound to reduce rolling resistance and maximize overall vehicle fuel economy without compromising other performances.
•Asymmetric run-flat inserts and carcass configuration are designed to broaden and emphasize a range of tire performances by focusing distinct functions to the appropriate sidewall.

The MICHELIN Pilot Super Sport ZP tire for the Corvette Stingray with Z51 Performance Package is different from the tire found on the Corvette Stingray.

The MICHELIN Pilot Super Sport ZP tire also features the next-generation of racetrack-born tread compounds found in the record-setting Pilot Sport Cup ZP of the C6 ZR1 and Z06. Unlike the MICHELIN tire fitted to the standard 2014 Corvette Stingray, the Z51 tire features a custom dual-tread compound and pattern that achieves near-racing-slick grip and handling levels, while providing longer tread life and wet handling capabilities.

Like the tires found on the standard Corvette Stingray, advanced computer-modeling techniques used to design American Le Mans Series racing slicks were applied to the Z51 Performance Package tires. The process resulted in tire structure and contact patches optimized specifically for racetrack-critical tire performances.





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Snorman

I realize that. And as with Corvette, Nissan designed and tuned the suspension around those tires. Now, with a non-OEM tire, the car doesn't feel as well. I'm not necessarily blaming it solely on the tire size, it's a function of changing tires. My comment was directed precisely to JustinStrife's questioning of people going to a non-OEM tire. With all the hoopla that surrounded GM going to a different tire, it stands to reason that GM has somewhat put their faith in the Michelins.
FWIW...I don't see Joe's posts. All he does is argue, and honestly, I have no desire to read them.
S.

sam90lx

I agree...once you have the Michelins from the factory I just cant see changing to another brand until there is something better.

VETTEMANN

Not to nit pick, but at least 2 of the cars on the list have AWD - helps when you have those fronts pulling too And the Shelby Mustang, even the Mustang, gets criticized regularly for have such skinny 285 rubber...

VETTEMANN

Very funny.

But it is kind of ironic that GM redesigned the Vette with the trendy C7 body to steal sales from Porsche among the younger 30-40 somethings ...the same Porsche-driving 30-40 somethings that valet park everywhere they can and go in through the back door in the thump thump night club scene...

theseal

Chevy is not presenting a sports car. This is a touring car. That means smaller tires. Better ride. Cheaper tires. Better mileage. Wider wheels would be appropriate for a sports car. All performance parameters would be improved. The marketing bs about lap times and miracle tires is for the audience that was hoping for a sportscar. Chevy's view of the larger audience, who doesnt care about this forum or sports cars, wont care much about the narrow tires. They are just looking for a cheaper jag or aston.

The real question is, can the car fit wider wheels and will they release a version closer to a sportscar.

BlueOx

The idea that the Corvette is and has been a sports car and a grand tourer is very old news. Maybe you should tell us what sports cars you think are better for the money.

Cheaper tires? Good luck with that.

ALL performance parameters would be improved just by wider tires? No.

Of course Chevy doesn't care about this forum. Of course they care about a larger audience. Duh.

Maybe you should wait to hear the lap times before you yammer on.

DREAMERAK

Since the C7 will out perform the GS, I guess that means the C6 Coupe and GS were not sports cars either, talk about BS!