Preparations for the upcoming autocross season.

[ActionMan]

This is the first season for me and my new S2000 and I'm in need of some tips and tricks. My car is bone stock, no modifications whatsoever, although they are allowed by the regulations. No restrictions as to what tires can be used either.

The "VK" series in Latvia has 5 races and takes place on different cart tracks, not on an airfield with cones. There's tirewalls and everything.

What would be the recommended suspension settings (camber/toe/etc.)?
I've bought a set of Goodyear Eagle F1 GS-D3's. 205/55R16 in the front, 225/50R16 in the back. I'm also looking into a possibility to get a second set of wheels with Toyo R888's. Could You recommend any other no warm up tires?

I've read the Autocross FAQ previously posted but the tires mentioned there are unavailable in my region.

[gomarlins3]

I have gone to the UK settings on the alignment, that seemed to help a little. I also use Kuhmo race tires, those make the most difference. I have also found that the Comptech adjustable front sway bar makes a difference, but goodluck finding one now.

[Scott]

I wouldn't recommend R compound tires if you aren't fully accustomed to driving the car to it's limits. They have fantastic grip, but the traction limit is a pretty abrupt one, and they don't give you a lot of feedback before they let go.

I think it would be best to go a season or two on some good street tires (the F1 GS-D3s are a great tire), then if you want some more stickiness, make the move up.

[bjurasz]

Search the Suspensions thread for the exact settings on the UK alignment. I'm going to try that myself soon. Scott has good advice on avoiding R-compound tires if this is your first season. I'd do the alignment and stick to the street tires for the time being. You do want to add air pressure when at the event though. Probably up to about 38 psi cold. Drop that before you drive home though.

There is so much to autocrossing that your car is not going to be the limiting factor your first year -- your driving skills will be. Spend the first year learning your skills. Spend the $$$ on mods next year.

[Java Junky]

I godda agree with Scott on the abruptness n' increased lack'a (hmmm-m-m , , increased lack? Sheesh!) the lessened warnin' that's sometimes a part of true race rubber, but, if you're gonna spend the time, effort, money n' risk out on a track . . why half-step with street shoes?
Again, I'm jus' goin' with what I'm readin' in the funny papers (posts), but AMan doesn't seem like he's totally new to this. Spendin' any amount of time on street hoops is only gonna require readjustin' when it's deemed time to switch to race rubber n' always leave ya wonderin' how much better times you could'a turned with the real McCoy.
Be well n' keep us posted AMan.
Java

[ActionMan]

Good feedback, thanks guys! The F1 GS-D3's do grip tremendously well for street tires (plus they give more feedback, probablydue to firmer sidewalls, than TOYO Proxes T1R's that I had on before the F1's). I'll look into Kumho offerings.

I'm failrly confident with driving at the limit of grip and fairly confident with my skills when the wheels do let go, thus the choice of S2000 above other cars. Yet, it's true that I've never experienced the grip and limits of R-compound tires. I don't have high expectetions for my first season. The drivers I'll be up against are eperienced and have numerous mods to their cars, plus the top5-8 usually have the R-compound (unless it's raining). I do have faith in my S2000 though and, given enough pracitce, preparations and experience with the settings, I'm fairly certain the S will shine in "VK" cup.

bjurasz, could You explain the tirepressure effect on grip a bit further? Overinflated tire would have a smaller contact patch, however it would be prone to less flex. Is that it?

[bjurasz]

Every High Speed Driver Education event I've been to, every autocross I've been to, say "put more air in the tires than you would on the street". From what I gather you put so much extra cornering force than you would normally see that you don't want to be rolling onto the sidewalls in the corners, or worse rolling a tire off its bead. If you put white shoe polish along the edge you'll be surprised how far down the side of the tire it will wear during an event. If the wear is too low down the sidewall you need more air pressure.

[gomarlins3]

Most importantly: Start to spin= both feet in!!! In other words, if the car comes around on you GET THE CLUTCH PUSHED DOWN as well as the brakes!!!!

[bjurasz]

Ok, I just did an autocross on Sunday and I think I have a bit more feedback for you. I'm using the stock 050 tires on a bone-stock 2006 model.

The 050's did a bit better than I thought they would. The general rule about pumping up the air didn't seem to apply to the 050's. I started with 38 psi cold but got a lot of understeer in the car. I eventually dropped to 34 psi cold and got much more grip, and more importantly balance in the car. I was also able to get the tires to squeal a bit rather than just slide.

Overall I was a bit more happy with the 050's than I thought I'd be.

More things I learned. If you are running SCCA rules you can run a "Tire" class if you use DOT-legal tires of a 140 treadwear rating or higher. The scoring people will apply a handicap to your time designed to offset you against those running gumballs. Something to consider, and I will probably go this route with my next set of tires.

The tire-of-choice for competition but still street driveable seems to be the Toyo RA-1 tire. Apparantly you can get them in stock sizes for the 16" shod S2000. For the 17" cars you have to compromise on size and then I'm not sure if you are T-class legal any longer.

[bjurasz]

One more update as I got more info last night about tires and wheels and SCCA rules. For a stock class you must have the same size wheel as factory stock. That includes diameter and width. But you can use any size tire you can fit on the rim and have fit. So you can over-size the tires if they fit on the stock rims and still run a stock class. Going to a 225 front and 255 rear on AP2's opens up a lot of potential choices for our cars that you don't have if you stick with the 215/245 stock sizes.

[carguy123]

Your Goodyears are "undersized" for their rated size, especially on the rear so you will get a lot more oversteer which isn't all bad in an autocross situation since that helps rotation.

[Scott]

The way I learned was that you put more than enough air in the tires, then after each run, let a little bit out until you find that perfect balance.

[ActionMan]

"undersized"? I just went with the stock recommended sizes and they fit perfectly my stock 16" wheels. I'd probably go with a bit more width up front next time as I do understeer in some of the tighter bends.

[carguy123]

Originally Posted by ActionMan

"undersized"? I just went with the stock recommended sizes and they fit perfectly my stock 16" wheels. I'd probably go with a bit more width up front next time as I do understeer in some of the tighter bends.

I can see that you haven't been reading many S2000 forums. The stock tires are wider than the rated size would indicate. This is most evident in the rears.

The rated size of a tire isn't necessarily the "finished" size of the tread. If you will check the actual width of the Goodyears you will find they are narrower than many other brands. I had a lot of trouble finding the real size of the Goodyears because Goodyear, and all the others that make undersized tires, don't make it easy to get that info.

Let me give you a couple of for instances. My first aftermarket tire on the S was the BFG KDs because I had heard about how good they stuck. The front tires were about 1/8" narrower than the S02s but the rears were over 1/2" narrower than the stockers AND that's despite the fact that I had gone up one size on the rear!!! The car handled horribly.

When I was looking for 18" tires I knew that I needed to preserve the front to rear relative rubber sizes/contact patch to maintain the same handling BUT I also wanted to up the limits by putting more total rubber on the road.

After much research I found that in the same rated size there was over a 2" variance in actual width between the narrowest and the widest tires.

I ended up with a BMW spec S02 for the front and a Porsche spec S02 for the rear. This gave me the proper rubber balance and upped the amount of rubber on the road considerably. My rears are slightly over 11" wide.

[Java Junky]

AMan, have you tried jus' adjustin' the pressures to balance the car's grip better: i.e. understeer will usually correct with more grip front, or, less grip rear. That's accomplished with a bit less pressure up front, or, a bit more pressure rear . . or, a combination of both. It's a real balancin' act though, so patience and subsequent testin' will give you the best chance'a nailin' it down.
'Bottom line is you have to have a base-line to start from n' if you're serious, take notes after each setting change n' test run.
But mind what's already been suggested about needin' more pressure to keep the rubber where it belongs when you're really pushin' it. The white shoe polish/yellow crayon on the sidewall will indicate to you when you're reachin' as low as you can pressure-wize.
You guys r' puttin' out some really good info on this post. Thanks.
Be well.
Java

[bjurasz]

carguy123, intereseting about the tread widths. I've been told by several autocrossers to move to 225/45 and 255/40 tires, mainly because it opens up so many more choices. The Yoko Advan AD07 is a top-choice for a "tire" class. Front tread width 8.5", rear tread width 9.9". Good? Bad?

[carguy123]

Regardless of the rated size you want to preserve the front to rear rubber balance or else risk changing the handling characteristics.

For instance, if you want to reduce understeer then increase the balance of rubber on the front.

As someone else said you can to adjust tire pressures to make minor changes.

This may help, it is the stock widths.

Stock sizes are
205/55 X 16 = 7.1” wide (83.5% of rear tire)
225/50 X 16 = 8.5” wide (1.197 times the size of the front)

[bjurasz]

And we want to know tread width, not section width, correct? I have an '06, so 17" wheels. But I'm not sure I beleive the Tire Rack's data.

RE050 215/45-17 6.7" tread width, 245/40-17 9.0", front tires are 75% of rear. But that 6.7" number sounds wrong. The section width is 8.3". Sounds too big a gap.

Yoko AD07 225/45-17 is 8.5" of tread width (on 8.9" section width) and 255/40-17 is 9.9" tread width, so front is 85% of back.

Section width of the front Yoko's is only .6" wider, but the tread width is 1.8" wider?

[carguy123]

Yes, tread width.

As a rule of thumb, if they don't list the tread width but just section width then the tire is narrower than other comparably sized tires.

I had no idea there was as much variance in actual tire sizes until I got burned with the BFG KDs. I had always thought the rated size was the real size. It pays, in more ways than one, to do a little comparison shopping.

For some reason the rears are the ones that have the greatest variance in sizing.

[bjurasz]

Interesting carguy123. Who would have thought tire sizes vary that much? I think I will go with that Yoko combination though, even though it appears to make the fronts a larger percent of the rears. Enough people autocross that combination that it probably does work.

[carguy123]

I like a larger percentage to the front cause I hate understeer.

[Java Junky]

'Agree with ya there CG. 'Ain't never been'a fan'a understeer myself.
As for the greater size differences bein' seen in the rears: with innaccuracies, the greater the numbers (in this case, the size'a the tires) the larger the innaccuracy. 'Multiplys as the numbers grow. Usually, anyway. Leastwize, that's the best guess I can come up with.
Be well.
Java

[ActionMan]

I actually did alright.
I ended up 13th out of 40 in my class (1.8 to 2.5 liters, N/A) in my debut race. My laptimes were pretty consistent and I managed 1'02".7 on several laps. By comparison the guy that won my class did a best lap of 0'59".8 and he was running race slicks (not DOT street legal R-compound), while I was driving on my undersized Good Year Eagle F1's. More than haf of the cars in my class were sporting slicks. Sure, You can't really calculate like that, but if slicks do give an average of 3 seconds off a one minute AutoX lap, then I'd have ended up on a podium on my debut race. so, I guess I did good.

[Java Junky]

Nice goin' AM. But credit where credit's due: you did better'n alright pal.
Thanks for the heddzupp.
Be well.
Java (Yeah AM. That's better'n jus' alright)