[mbar]

Thanks Eric. Sounds like I should look for 19x10 with 20+ offset.

[Eric SS]

Originally Posted by mbar

Thanks Eric. Sounds like I should look for 19x10 with 20+ offset.

That would be ideal. I went with Apex because they have a good reputation on the track and were pretty cheap.

[Norm Peterson]

Originally Posted by mbar

Thanks for the info. I thought the car /computer might go bananas if the overall wheel diameter significantly changes

The bigger problem is differences in tire revs per mile, front vs rear. Differences that are too big (compared to OE differences if the OE setup is staggered) can make the ABS module think that the smaller diameter tires are closer to lock-up than is actually the case. If there's a maximum deceleration rate, it's going to be way up there.


265/40's on 9.5" wide is not a 'stretch' (9.5" is actually the "measuring width" for that size in any diameter). Change your '19' to '18' and you've got my DD setup. Which if anything, is a bit soft-responding and less precise compared to what I do run on the track with - even though the tread widths are the same.


Norm

[mcynet]

Im running factory width with 19" MRR rims and have a 285 Square setup . Im running the same setup as the GM Engineers are running on thier auto cross car.

[mbar]

Originally Posted by mcynet

Im running factory width with 19" MRR rims and have a 285 Square setup . Im running the same setup as the GM Engineers are running on thier auto cross car.

1LE factory width? (10X19 F / 11X19 R )
285/35/19?
Negative camber on the front?

Thanks

[mcynet]

Originally Posted by mbar

1LE factory width? (10X19 F / 11X19 R )
285/35/19?
Negative camber on the front?

Thanks

NO 2ss 8.5 F 9.5 R

Max Negative Camber on front i think we hit -2.3 R -2.1 L and some on the rear. I think the rear is -1.7 on L and R

[mcynet]

Originally Posted by mcynet

NO 2ss 8.5 F 9.5 R

Max Negative Camber on front i think we hit -2.3 R -2.1 L and some on the rear. I think the rear is -1.7 on L and R

the front it tow out 1/8in because the pinch on the tires to allow quick turn in and I have a front bar and end links.

[mbar]

Originally Posted by mcynet

NO 2ss 8.5 F 9.5 R

Max Negative Camber on front i think we hit -2.3 R -2.1 L and some on the rear. I think the rear is -1.7 on L and R

Thanks. I assume you stayed with stock width to keep the same class? (don't know much about AX rules)

[Norm Peterson]

Originally Posted by mbar

I'm trying to save money

Is this for a dedicated track setup (plus the driving to and from the track) or is it going to be pulling full dual-duty?

In the available wheels, is there a big $ difference between 9.5" wide and 10" or 10.5" wide? If not, and if tire pricing is such that you do have to go with 265/40's this time around, know that you can mark time by fitting them on wheels all the way out to 10.5" (max recommended width) which leaves you some room to grow next time around.



This past weekend I finally got to drive a 6th gen, briefly but hard enough to get some slip angles going on a couple of occasions (the owner is the other grandpa to two of my grandkids). 245/40's on 8.5 and 275/35's on 9.5 just aren't enough (but you know that). Even 265/40's on 10" would be a significant enough upgrade to be worth considering, with the idea of 285/35's later on in mind. For 295's or 305's you'd be better off getting 10.5" now, I don't think even I'd try stretching 265/40's all the way out to 11".


Norm

[Super Speeder]

Im on 275 square on OE wheel widths....

Apex, your pic shows FS class - Are you running a square setup in FS? i didn't think that was allowed?

I am currently trying to figure out if i want to buy RE-71's for my winter wheels (stock 20" sizes) or go with a wider 19" setup and move to CAM. I would prefer to stay in FS but I also would like to have a wider tire on the front.

[Norm Peterson]

Originally Posted by Super Speeder

Apex, your pic shows FS class - Are you running a square setup in FS? i didn't think that was allowed?

Tires can be 'square' in Street Category (or any combination of sizes you want that can be physically mounted on class-legal wheels).

It's the wheels that must remain OE width (in either OE diameter or OE diameter ± one inch).


Norm

[Super Speeder]

Just to be clear - I can run 9.5" wheels on all corners even thought it came with 8.5" on the front?

[DetCam]

Super Speeder: Just to be clear: NO.

To run in FS class, you have to have the same width WHEELS as what came on it. Tires are a different story... squeeze on anything that will fit.

You can go up or down 1" in diameter (either 19" or 21" dia. wheels). Most of the top guys in the Autocross world went down to a 19" diameter wheel. Same staggered widths as stock (8.5 and 9.5 I believe). BUT, they did squeeze a 275 or even 285 width tire onto all four corners. The fronts were "bulging" out a bit more on front rims as technically that is not the "correct" size tire for that rim, but it did work. It was not technically a "square" setup, as they could not rotate their wheels front to back. To rotate the tires around, you have to get them dismounted/remounted on the wheels.

Note: One of the first reasons they did this was there were more tire options in the 19" size than in 20's. More brands to chose from, and a little less money for the smaller size. (Granted, those light weight wheels more than offset any cost savings, as they are NOT cheap... hence the stock wheels still being on my car). PLus, the 19" wheels ended up with a slightly shorter tire, which provided a better gearing ratio at the lower speeds.

There are rules regarding offset as well, but most of the top guys were running light weight wheels with just enough offset to allow the wider tire up front. The only problems that I've ever read about was the ABS occasionally kicking into what they called "ice mode" where it just wasn't calibrated to have SO much traction. (More tire, plus stickier compound autocross tires, and you're stopping on a dime and making change).

[Super Speeder]

DetCam, Thanks for the clarification. That was how I interpreted the rules - hence my confusion.

So I'm back to deciding whether to get 19" wheel/tires, or 20" tires for my winter wheels.

I was originally thinking of going with 255/40-20 front, 285/35-20 rear RE-71R's. My winter wheels weigh 25.6/27.8 lbs F/R - So the cost of 19" wheels to save a few lbs doesn't see too beneficial. I think the benefit would come more from the lower gearing of a smaller diameter tire.

Anyone have thoughts on these two options?