Swapping from 17/18 OEM Street to 18/18 Autocross
 

I'm looking to run my OEM 17/18 wheels with street tires (265/295) in my stock '02Z for street use, and then swapping to a 18x9.5/18x10.5 setup with Rival-S (275/315) or RE-71r (265/285) for A-street autocross. Car isn't lowered. Is there anything wrong with this that I'm missing? Does the suspension need to be altered? Is there a better way to go about running a good set of 190+TW autocross tires within the A-street rules (+/- 1" diameter rim, 9.5" rim up front, 10.5" rim rear)?

The only thing you're missing is a 19x10.5" rear wheel to run the 305 RE-71R. The current AS setups are either the 275/315 Rival S or 275/305 RE-71R. So you're close, but go with the extra tire.

OT they have autox in Alaska? My daughter & son-in-law lived/worked there a while. I have visited, great place (in the summer).

:)

The fast AS guys all run a 275 front tire, regardless of their chosen brand. This helps add front grip. The rear tire is a choice between the shorter BFG, which some people like, or the extra gearing and steering precision of the RE-71R. If you're running AS, these are your best options to be competitive. Anything else will be leaving performance on the table, IMO. Ignore what most people do here, and look at/talk to the folks that are competitive at National events. Most people here are either slow, or never leave their local lots (or both), though looking at my piss poor Nationals experience, I definitely fit in the former group.

If you want to forget about AS, get an extra pair of 18x10.5 rears, run 315 square Rival S' and run in CAM-S. The plus side here is that you can mod your car in whatever way you desire, and there are basically no limits.

Sorry, I deleted my post because it was a double post, but a mod got it, so now both posts are gone (I'm new here) :hide:. Thanks for the advice.

Froggy: Yeah they do have AutoX in the summer! SCCA runs 14 events, PCA runs 8. They're generally low speed/technical courses. Not looking forward to having to put the car away for the winter...

Just as a reinforcing opinion, I agree with mattastick's recommendations: use the bigger rear tires whether you go with the Rival S or RE71R. I'll add that the two tires drive quite differently, although I believe that they have pretty equal speed potential. If you can possibly do it, try to get a drive in cars with each tire to see which one you like better.

I ran 285/305 re-71 in A street with 18/19 front/rear aftermarket wheels...rules legal.

Why 275 up front? With max camber (I think -2.7ish) and lowish pressure (26-28 hot typically) I used every bit of the front 285s.

They fit just fine up front. If anything the 305s look more oversized to the wheel than the fronts as I struggle to get to the wear marker.

Still running this in cam until I wear out the fronts and switch to the cam rival setup.

Good question. The 285/30/18 RE71R is almost an inch shorter than the 275/35/18, and that makes it 1.4" shorter than the 305/30/19 rear. That would be my main concern with that 285.

Great call-out.

I think I reset my ride height and rake with the new wheels/tires on but now you've got me doubting myself.

​​​​​​I've never had a problem with active handling or abs using this setup for autox and hpde for anyone who is curious.

To be fair, I'm not sure exactly how all the effects of this add up. It might even be a good thing. And the fact that the C5 is fully adjustable for ride height in Street/Stock class may mean isn't all that important. It will still change the roll geometry even if you keep ride height the same, but that could be good or bad depending on a lot of other things.

18x10.5 square

Not for A Street solo competition - can't go wider than stock.

Can't do a lot of good/typical stuff in A Street....no CAI, no LT's, no dyno tune, no smaller steering wheel.

A-Street won't be the class for me. CAM-S HERE I COME!:willy:

I'm there now. But be warned, if you run 10.5" square in CAM-S, you'll be in the narrow-wheels club!

True, BUT 315/30/18 Rival-S are getting plentiful and cheap at the end of each season. The most common 18" tire. Or the 335/30/18

Definitely. It's just that most people run the 315 on an 11" wheel. The 10.5 will work - it's just not optimal. How much of a difference it really makes, I don't know. The 335s are mo' bettah, but on my C4 they would require flares to tuck properly with a lowish ride height. They are also taller tires, so there are tradeoffs.

Yep. It's super easy and cheap to go 18x10.5 C5Z rear wheels all around and 315/30/18.

Outside of that you are buying Forgestar wheels with capability of custom offsets for 18x11 or 18x12. And beyond that is Forgeline....

So yea, I'll stick with the easy button :) I don't have the wallet to play THAT hard.

275/18 305/19 RE71 is damn near the exact same tire diameters as the OEM 265/295. Your car will be exactly the same height and have the same wheel gaps. No changes needed.