Cal Club Autocross Forums

Arthur Grant wrote: I don't think the 295/35/17 Kumho is a useless size. For those of with multiple sets of 9.5" wide wheels the 295 represents the widest tire we can fit on that wheel. For the back of a torque machine like my C4, the 295's make great rear tires, and if I want to square up decent fronts. Would prefer a lighter tire, but since I am not going to be running for a championship in the next couple of years will trade wear for a touch more speed.

The issue for me are the comments on camber. The Vette is camber limited (about 1.7 degrees) so it may be the Hoosiers are not as suitable.

It is a turd, there is no polishing it. I spent nearly ten years in multiple C4s, all of them on Kumhos. The C4 already turns in slow, the 295 only hurts it. And the C4 does not have enough power to pull that big rear tire. You may not think so, but you are hurting your acceleration with it. There is a reason all (except one) of the top C4s have been 89's, it is the early 3.54 gear, extra grunt coming out of the turns. The taller tire only makes it slower, especially if you have an already taller geared car.

A 315 can easily be fit all around on a C4 with 9.5" wheels. In fact the only non-89' C4 to win Natls was Matthew Braun's LT1 car, with 315s all around.

Jason Isley BS RX8 wrote:In fact the only non-89' C4 to win Natls was Matthew Braun's LT1 car, with 315s all around.

Are you talking about only Stock classes? Not Street Prepared?

Christine Berry wrote:

Jason Isley BS RX8 wrote:In fact the only non-89' C4 to win Natls was Matthew Braun's LT1 car, with 315s all around.

Are you talking about only Stock classes? Not Street Prepared?

Of course... Who else would run a skinny 17x9.5" wheel.

Aaron Goldsmith wrote:Nationals SS results show them to be fairly equivalent with top tier drivers. Hoosiers perhaps having a slight edge. We go with who rewards with contingency.

Referring only to THE nationals, back when I had a C5,(08 maybe?) I checked every SS Corvette on grid. Every Corvette in the top half was on Hoosiers and roughly 50/50 split on 275s vs 295s front. I think all had 315 rear. Many had tried Kuhmos and generally agreed 25% to 50% longer life...but here they were on Hoosiers.

The V710 and A6 have both been around for many years. Use of Kumhos at the national championships has dropped dramatically since the hiatus in Kumho's contingency prize program, so your best chance of finding both tires represented by "top tier drivers" is to look several years back, especially during the time before Kumho dropped the contract driver program.

Jason Isley BS RX8 wrote:

Arthur Grant wrote: I don't think the 295/35/17 Kumho is a useless size. For those of with multiple sets of 9.5" wide wheels the 295 represents the widest tire we can fit on that wheel. For the back of a torque machine like my C4, the 295's make great rear tires, and if I want to square up decent fronts. Would prefer a lighter tire, but since I am not going to be running for a championship in the next couple of years will trade wear for a touch more speed.

The issue for me are the comments on camber. The Vette is camber limited (about 1.7 degrees) so it may be the Hoosiers are not as suitable.

It is a turd, there is no polishing it. I spent nearly ten years in multiple C4s, all of them on Kumhos. The C4 already turns in slow, the 295 only hurts it. And the C4 does not have enough power to pull that big rear tire. You may not think so, but you are hurting your acceleration with it. There is a reason all (except one) of the top C4s have been 89's, it is the early 3.54 gear, extra grunt coming out of the turns. The taller tire only makes it slower, especially if you have an already taller geared car.

A 315 can easily be fit all around on a C4 with 9.5" wheels. In fact the only non-89' C4 to win Natls was Matthew Braun's LT1 car, with 315s all around.

If the 295 hurts the turn in and acceleration, wouldn't a 315 be worse?

Jason Isley BS RX8 wrote:

Christine Berry wrote:

Jason Isley BS RX8 wrote:In fact the only non-89' C4 to win Natls was Matthew Braun's LT1 car, with 315s all around.

Are you talking about only Stock classes? Not Street Prepared?

Of course... Who else would run a skinny 17x9.5" wheel.

I am not sure what to make of that. Since I have 3 sets of said skinny wheels the answer would be me?

Arthur Grant wrote:

If the 295 hurts the turn in and acceleration, wouldn't a 315 be worse?

No, the 315 is the same diameter as the 275, so acceleration will be the same - less the effect of a few extra lbs of tire. The short sidewall will react quicker than the monster drag slick like sidewall of the 295, however, pinching a 315 on a 9.5" is not ideal for turn-in. The 315 is the lesser of the two evils, but you really need to get it on an 11" wide wheel to use it. A set of four GS rears are a perfect fit.

I like the A6s, especially if you only have one driver. At many events this year my fastest run has been my first on the hoosiers. The 710s I think like a little more heat. I do have a biased opinion though, A6 rubber is my drug of choice.

Jason Isley BS RX8 wrote:

Arthur Grant wrote:

If the 295 hurts the turn in and acceleration, wouldn't a 315 be worse?

No, the 315 is the same diameter as the 275, so acceleration will be the same - less the effect of a few extra lbs of tire. The short sidewall will react quicker than the monster drag slick like sidewall of the 295, however, pinching a 315 on a 9.5" is not ideal for turn-in. The 315 is the lesser of the two evils, but you really need to get it on an 11" wide wheel to use it. A set of four GS rears are a perfect fit.

I have considered going buying a set of 11" for the rear, running 275 front and 315 or 335 rears. Alternately I have considered and with Mako's help plan to test the idea of running a C5 Z06 18X11 on the rears to see if that works.

Arthur Grant wrote:

I have considered going buying a set of 11" for the rear, running 275 front and 315 or 335 rears. Alternately I have considered and with Mako's help plan to test the idea of running a C5 Z06 18X11 on the rears to see if that works.

You want to make the car push? Don't stagger a C4. 315s on 11"s all the way around.

As the original poster on this thread, I've got to say the topic has been regained, and everyone profits. Keep it up. Good info is coming thru.

FWIW - because I had one Kumho front (story not included), I ordered a 3 tire set from TireRack (using the CSCC link). This does not preclude a set of Hoosiers on my next go-round. I'm getting the sense that the majority think Hoosiers are a few tenths quicker but have a shorter life. Probably pretty hard to quantify where the fall off is between the two. It seems most folks think Hoosiers do not require as much heat as Kumho's, which I think is significant for 1st runs at championships. My experience is the first lap on 710's is used for tire warming. No way to actually go fast.

Jason Isley BS RX8 wrote:

Arthur Grant wrote:

I have considered going buying a set of 11" for the rear, running 275 front and 315 or 335 rears. Alternately I have considered and with Mako's help plan to test the idea of running a C5 Z06 18X11 on the rears to see if that works.

You want to make the car push? Don't stagger a C4. 315s on 11"s all the way around.

Thanks for the advice. Given the budget I am probably looking at 275's all round. Plan to stay with Kumho, 1/10 of second, even full seconds due to tire wont make that much difference at this point, there are clearly several seconds to be gained just by learning to drive. I am getting my butt kicked by Evo's and BMW roadsters running on street tires.

On the Kumho vs Hoosier front it sounds like it could be very venue dependent. If they really wear as claimed and we run a number of events at El Toro on hot days, there may be a advantage to Kumho. Venues like Auto Club and Norton would be advantage Hoosier. What would be nice is one of the more capable and financially independent drivers with data logger system installed run new versions of each. Bet a pit crew could be pulled together to allow the back to back comparisons.

The short sidewall will react quicker than the monster drag slick like sidewall of the 295, however, pinching a 315 on a 9.5" is not ideal for turn-in. The 315 is the lesser of the two evils, but you really need to get it on an 11" wide wheel to use it.

Does anyone have an opinion on running a Kumho 315 on a 10" wheel or running a 335 on an 11" wheel?