For the past 3 years i've been autocrossing my 88GT on street tires and this year i finally scrounged up enough money to buy some R-compound tires. My car has koni specials front and rear .5 and .75 stiff respectively, WCF 1.5" front drop springs 350lb/in, rear coil over's 350lb/in, all poly suspension bushings, stock front and rear sway bar, -1.75* camber 9.5* caster ~1/16" total toe in front, -2.5* camber and ~1/32" total toe in back. My current street tires are 205/40/17 Kumho MX all around and i run them at 40psi front and back. My new tires are 225/45/17 Front and 255/40/17 Rear Kumho V700 Victoracers. I've heard that R-compound tires should run lower pressures but i'm not sure how much lower. Any ideas on what tire pressures i might try starting out with?

Atlast, a fellow autocrosser! Sounds like you have done quite a bit to get to this point. I have been running Goodyear Eagle LS for the last couple of years with 38 psi front and rear. Front end has 2 degree camber, 1/8" toe out, and 1 coil removed from stock springs. Rear end has 1 1/2 degree camber, 1/8" toe in, and 1 coil removed from the stock springs. Stock sway bars at both ends. My next step is to get some tires like your R-compound. I have also heard that you need to run them at a lower pressure than the street tires. Each track and outside temperature will affect the wear / contact patch. I am going to assume you already know about the shoe polish trick. But I will go over it anyway, I would start at 30 psi, dab a blot white shoe polish at 3 or 4 place around the tire. Right where the side wall and tread meet. Make a hot lap and look to see which part of the shoe polish is worn away. If it is up into the sidewall, then the tire psi is too low and the tire is rolling under. If no or very little is worn on the tread side, then you have too much psi and the tire is not using the whole tread contact patch. You know when you get it right when the round blot is worn away completely on the tread side and right upto where the sidewall starts. I usually change the pressure in at least 2 psi incriments till I get what I am looking for (keep in mind that you will gain 2-3 psi as the tires start to heat up).

There are more autocrossers on here then you realize. Including someone in a Finale...

I have been told to start at 5 psi less than you run in your street tires at events. I have also never had the money to run my own R-compound...

Do either of you mind if I add your suspension set up to the table I want to put on my website?
I would love to list any and all mods that autocrossers are doing for their cars...

EDIT: My avatar is from a Florence, SC event.

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2005 Smart ForTwo
1986 Austin Mini
1986 Fiero GT 5-speed (waiting on a brake upgrade)
2007 Ninja 500

[This message has been edited by midengineracer (edited 02-01-2007).]

yup, you can add my setup to your table if you wish. I guess i'll just go to the track with 40lbs and start lowering it from there. I was just hopeing somebody was running similar tires and could give me a rough idea of where to start.

Quickest way I've found is to use the tire temperatures. Check them with a pyrometer (an infrared thermometer kind of works, but it's not the best) on the outside, center, and inside. Try to get the temps as even as possible.

We don't autocross the Finale much anymore, we have the race car for that now. The hardest part, for me, is getting enough heat in the tires on a cold day, but on a KS summer day, the temp method can have it dialed in by the third run. 40 psi is probably a good place to start, I usually start at 38 rear and 35 or 36 front, but I have a light front end.

John Stricker

quote Originally posted by Zac88GT: yup, you can add my setup to your table if you wish. I guess i'll just go to the track with 40lbs and start lowering it from there. I was just hopeing somebody was running similar tires and could give me a rough idea of where to start.

Yes, you can add my info also. I think I am going to take the cheap way out, I have a set of aftermarket 14" rims, I would like to use a 17" rim, but I think I can get a 205/50-14 for around 50$ apiece. Even though the rim is smaller, I feel the better rubber compound will outway the 16" street tire I am using now.

If I had ever gotten the money, I was going to put 13s on my MR2 and run something like a 245/40 or something close to that. A little shorter for 'gearing' and much wider for the stickyness. I used to be regularly beaten (significantly) by a Miata with a similar set up. I think there are 13s that will fit the Fiero and if you are in Street Prep, you could get a reasonable advantage out of that set up. I think the really big detractor was that the only company making the size was Hoosier and I didn't have that kind of money. I still don't actually!

Thanks for the info and I will make sure to credit it. Unless you don't want your name listed on a racing site, insurance reasons and all...
I still remember all the new EVO owners taking off their license plates so that Mitsubishi wouldn't void their vehicle warranty.

well i had to go 16 or 17 because i have 12" brakes, i'm not concerned with classing, i just race for raw time. My car is E Mod i think, i dont pay to much attention to it. i have a N*, suspension stuff, power steering and more so whatever that puts me in. less and less 16" tires sizes are being made and more 17's are showing up so thats what made me go the route i did. Some of the fastest streetcars i've seen were miatas with modded suspension and nice wide 13's.

<-- got suckered into becoming the President of an autocross car club for the next 2 years.

I ran with a set of Hoosier R3S04's for a few events a couple years ago. I was ending up around 28-30 psi, roughly. I think that's probably where you'll end up as well.

You should hop the ferry over here sometime and play. There's a serious lack of Fieros racing over here. We need more! I've been building my engine for the last year, so I guess I'm not helping!

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'88 Pontiac Fiero GT - 5sp, 3.4L crate engine (in surgery)
'91 GMC Syclone - #449
'02 Yamaha V-Max - helps me poop

Rcomp tire pressure is gonna be dependant on size and brand too. I usually run 28-30 in my AS30x's. I have a fellow club member who has a temp probe. See if anyone in your club has one. For the past couple years I've run 225/50/15's for the lower cost over 16's & 17's and because 14's don't clear my calipers. I have a guy with some slightly used slicks for cheap money that I'm gonna use for this year.

The Fiero racers are scarce down here too. We had an 86 GT Auto with T-tops show up in January and said he'd be a regular. We'll see.

I have only done one season of autocross in my 85GT. I got R-Comps halfway through the year and found that about 30 psi did well. I got very frustrated on the street tires. My setup is similar to the original post, and the car does very well when I can drive it without hitting anything.

Z28, I used to run in the dixie region with my MR2, I was always looking for a Fiero to replace the MR2... It is times like now (you mention a race in January, how sweet it is) that make me consider coming back to the states before my original plan...

My first run driving R-compounds gave me the same adrenaline rush as the first time I autocrossed, it is so different from running on street tires!!!
Of course, I have beaten R-compound tires with street compounds on more than one occasion. I need to get back to racing before I lose all the honing of my little bit of skill.