Best Tire and Rim selection for autocross (FC3S)
 

So I recently got into autocross in a major way.
When I began, I had 245's all around on my FC which are considerably wider than the stock 205's, and they are on 17 inch rims to boot. The tires are somewhat old, but they seem to make the car slide around more than it should. I thought about it, and decided that it could probably screw the handling up since the weight is displaced over a wider area. I suppose this could cancle out the benefits of a wider contact patch, but I don't really know enough about suspension tuning to make a ruling.

I'm thinking of getting a set of 16x8's and running some 225/45R16's, my thoughts being that you get slightly wider contact patch with slightly less weight displacement, but the tire will be somewhat stretched on to the rim (reccomended is 7 to 8 7.5 being ideal for the tires I want to run) causing a squarer sidewall and as a result slightly better turn in.

I've got AGX's all around and suspension techniques sway bars. What else would be good without going to too crazy (I don't feel I need coilovers)?

Any help, thoughs and comments are appreciated.

Thanks,
Sam

Wider tires equals more grip, period.

If you are sliding all around, it's because:

*you aren't driving properly
*the tires aren't very good or are worn out
*the suspension isn't set up properly -- springs too stiff, shocks too stiff, anti-roll bars too stiff
*the alignment isn't setup properly

best advice i can give you is to go to the autox course and see what the guys that run up front are using.

if you are just starting out, chances are that you have to upgrade the nut behind the wheel. ;)

The mod of this forum (DamonB) has many very good threads and articles in the Suspension/Wheel/Brake Archive forum so check that out and start learning about suspension setup before you start pissing away your money on parts you might not need.

Please since you are local come by our place in Milpitas, www.autornd.com.

Address is at bottom of page. We work with FC's and are one of the few places that offer a lot of support for them. Dana and I are great with this stuff but would like to look at your car and under your car to do a thorough evaluation to arrive at a proper solution.

Hope to see you soon. We are returning to the office on tuesday. Several of my FC's are there, including my GTUs which we have setup for similar purposes.

16" is great for soloII. Other questions we have are class spec etc... Are you doing for fun or to compete? For fun i mean compete against your own time. We can assist you with setting up your suspension settings as well and will take a look into possible suspension mods you have that are not necessary for acheiving your objective. More isn't always better.

Not sure how you are fitting a 245 up front without coilovers, but a 235-45-17 (on a 17x8) RA1 is a good choice for a beginner R compound AX tire. You will be blown away by the difference. If these are not dedicated race wheels, then the Kumho MX is your best choice by far. Regards, Carl

agreed that wider is better, period.

for you I'd suggest some 245's up front and 265's out back, on 16'' wheels, getting the right width and offset will allow these to fit no problem if the car isnt lowered too much. the falken azenis and kumho mx are excellent tires for street/roadtire classes and will also be great on the street. see if you can run the widest, lightest 16''' wheels possible, it will make a noticable difference if you put that 265 rear tire on a 9'' wheel compare to an 8'' wheel.

are you buying wheels and tires only for autox or also for daily driving?

I kinda have the same question. I posted this in Race Car Tech, maybe I shoulda posted it in here ---

I posted this in Race Car Tech, maybe I shoulda posted it in here ---

Hey guys,

I'm getting into SCCA autocrossing. I did it 4 or 5 times last year with a different car but this year I've taken out my 90 GTU N/A to 2 events. I think I want to stay in E Stock class because I don't have the money, time or facilities to do extreme or expensive modifications.

The first event I went to, I got some bad oversteer, the back-end wanted to come around bad. I looped it and actually spunout once, did a 360. "Hang on, Gomer!!!" :)
This was with a set of street tires from my other car. I swapped another set of street tires for the other event last weekend and cranked up the pressure all around (44 rear, 34 front) and it seemed to do better. At least I didn't loop it and the rearend seemed to be more stable... or maybe I wasn't driving it as hard because I was "gun-shy" about the oversteer. Anyway, I didn't do so hot with the times.

I know R-compound tires make a BIG difference. I'd like your advice and input from your experiences and knowledge, please.

I think I can pick up a set (4) of used Hoosier R3S04 tires for about $200. I may be able to get either 205x50x15 or 225x45x15. According to SCCA rules in Stock classes, I need to run stock rims. I believe my stock rims are 6", is that correct? If so, then are the 225x45 tires going to be too "pinched"? These being wider might be better but if they don't fit my rims well, I may be better with the 205x50. If I can get either size, what do you think?

Of course I'd rather have new tires but not really in my budget. If I had the money, I think I'd go with Kumho V710 or Avon Tech R instead of Hoosiers, but I really don't want to spend $600 - $700 for new. As I said, the used Hoosiers are R3S04, not the A3S03 or 4. I'm sure the A's would be better than the R's, since they're autocrossing tires instead of roadracing tires and supposedly come up to heat faster. But I'm limited on my selection of used and don't really have a choice so I this may be what I have to go with... or am I wasting my money?

Ok, guys... jump in with your comments, suggestions, etc. on this, please. I appreciate any input you can offer. I'd also appreciate any other suggestions you may have as far as other things I can do to the car and still remain in E Stock class. Also, is my 90 GTU actually competitive in this class? And, yes, my driving skill and talent needs to be "refined", I just want to be as competitive as I can be and kick some ricer butt!!!

Thanks!!! :)

You're wasting your money. Forget the fancy tires and learn how to drive first. I think your tire pressures are way too high, personally, especially if those are cold pressures.

44 isn't bad if it balances the car the way you want it just remember to deflate it back to normal psi for the drive home. But learning to drive is really just as important. Go to an SCCA driver's school. Have the instructor take you out in your car, if he has experience driving a 7. You will walk away a better driver. Tires do make a difference once you have had some instruction and maybe 5-6 races under your belt. Look for a set of Yokahama A032R type S. I have autocrossed on the non S type before and they are superb - the S type should be even better. I have a gut hunch that they are better than the SO3s I just took off my car. They won't last long though if you leave them on your car and drive to work every day. LOL.

Best selection? really depends... I was using 225-50-14's RA-1's for a couple of years. I also tried a set of 205-55-16 but went back to the 14's cause I lost about 4seconds on a 60 second course. I say go smaller dia and wide as possible.