regganib

Anyone been autocrossing with Rivals on a C5Z yet. I’m changing to an 18/9.5 front. SCCA street class allows +-1” on rim diameter. 295-35 front is too tall to be used with 315-30 rear. Considering tire size cominations F275/R295, F275/R315, or F295/R295. Would a 26.1” tall 295-35 be too tall for front end lowered with stock bolts?

froggy47

talon95

Seems like 275/315 to me, or maybe 275/295. Depends on whether any more grip can really be had going more oversized with the 315. No way to know for sure without testing. But I haven't tried any BFG's yet.

gunluvS14

I'm assuming you are doing SS or AS.
We did 2 regional event on the Rivals so far on aslphat, not bad actually. In fact, it surprised me quite a bit. It's no A6 but let just say I'm very pleased with it.

Once thing I noticed it is not that difficult to drive fast. A lot of people complaint the car is undriveable without R-comp. I disagree.

We shall see how it goes in 2 weeks at Dixie Tour

Gordy M

Street tires like Rivals do not like being oversized for the rim so the 275 front might work better. I ran almost half the year on BFG's and found them to be very predictable, but I had to refine my driving habits. Stay within the tires as they recover slower than R comps, they do like low pressures...32/31 hot, and are consistent from the first run. If they over heat, then its like the old days and water them down between runs. HTH

talon95

Yea, that and the 275 has a shorter sidewall. I suspect if you gained any steady state grip at all with the 295 front, it would be lost in transitions.

regganib

gunluvS14 , Gordy M,
What sizes are you using?

I was originally thinking that the 295 might work front and rear since the 9.5” front is only .5” smaller than the recommended rim width. I was more concerned with the clearance of the 26.1” tire.

talon95

The 295 will fit on the front. Back when we ran 710's, some of us tried the 295/40/17. It's the same diameter (26.1) according to the specs. IIRC, it rubs slightly at full lock on the rear of the fender, but not enough to be an issue.

Gordy M

For 18" rims 9.5/10.5 wide the 275/295 combo will work the best. Tirerack has the dimensions on their website for that size wheels and it is very close to the oem tire configuration heights so the abs will be happy.

mountainbiker2

What front rims are you using? The size has to be 18x9.5

thanks,

Steve

froggy47

regganib

[QUOTE=mountainbiker2;1586321141]What front rims are you using? The size has to be 18x9.5

There are plenty of 18/9.5 wheels out there. Try any of the true race wheel companies or you can go a less expensive route by looking at knock-off style wheels that can be found at places like OE wheels or most Corvette sites.

regganib

Did the tire rub on the actual fender or the fender liner?

talon95

The liner and it just barely touched IIRC. No damage. My wheels at the time had the .25" max offset too which might push it further toward the liner.

ltborg

I'd go as close to the measured rim width for the tire as possible. Maybe 0.5" narrower if it gives you better tire options. I just picked up 255/285 Hankooks for my BS (formerly AS) car. Just for comparison, the hote setup on race tires was 295/315.

talon95

Which would be a 275/295 combo for C5Z wheels according to the BFG specs.

ltborg

Yeah, that looks pretty good to me too.

justkickin

Has anyone tried the 295/315 combo on the Rivals? That is what I was thinking of using.

Still have about 3 feet of snow on the ground here so I won't be racing any time soon.

regganib

A local guy has run a couple events with that combo and says the abs isn't happy. The 295 is quite a bit taller than the 315

ltborg

The only time my car has gone into ice mode with ABS is when I run a smaller rear tire than front. I've never seen ice mode engage with a square setup or a setup with a smaller diameter front than rear tire.

The 295 is also not specified for a 9.5" rim. I know people have done that on Hoosiers, but those tend to run small for the size on the sidewall. I have no idea if the Rivals run small, but if not, they would not work well on an undersized rim.