ok so i am autocrossing my 89 gtu tomorrow and i want to know if it would be better to run on my 15 inch vert wheels or my 17 inch SSR wheels...


the 17 are 8.5 front with 215
and the rear are 9.0 with 255's

 

What class are u going to be running in? If its the stock class use the vert wheels, if its the sts2 class you might want to try the bigger wheels. As long you don't have any problems with the front end pushing when you are trying to turn, due to having the wider tires in the back.

 

Those miata's and crx's are tough competition in the sts2 class, at least the ones that come on a trailer. Is this your first time doing autocross?

 

im running in the class where its just mostly bolt ons... and minor suspention mods.. like strut bars and springs and under braces.

 

Thats sts2 you want then.

STS2 will follow the STS rule set, but the eligible cars will be restricted to two-seaters with engine displacements of 1.8 liters or less. This class will provide a home for a number of popular vehicles, including the Honda CRX and del Sol, Mazda RX7 (non-turbo, '79-'92) and Miata ('90-'97), Toyota MR2 ('85-'89), as well as other similar vehicles. STS category rules 14.1 to 14.10 apply. Further, as in STS, only original equipment viscous limited slip differentials are legal in STS-2.

 

This will brake down the classes for you.
http://cms.scca.com/documents/Solo_R...categories.pdf

 

Its gonna understeer like a pig with the SSRs. Run the vert wheels. Actually, what kind of tires are on each?

 

vert wheels have decent tires.. jsut cheap ****..

ssr's have good ****...

and yes this is my first time auto x'ing

 

Can you be specific? People have great variance in what they consider "good" tires.

 

If its some cheap tires with a low treadwear rating like, 400 AA or under I might run those.

 

I say bring both sets of tires & rims then switch them half day and see which really works better. The Miata's will blow your doors off, but it's still fun. I was put into CSP with my old N/A with tons of mods, I thought you had to have internal engine work to be STS? Anyway have fun.

 

No internal work allowed in either class.

Also, if this is your first time, pump your tires up to ~40 psi, take any loose junk out of your car the night before, and LISTEN TO YOUR INSTRUCTORS! Unless your bloodlines contain Moss or Schumacher you will get killed at your first event.

 

the 17inch SSR's
the fronts are nittos with 80% tread
and the rears are sumotumos with 90% tread

 

you might as well take the comvertible rims, mismatched tires dont help a lot, especially with that stagger, you'll understeer

 

when i did auto x with my vert i had 205/55/16s all around the car and into the day it started to push the front end a little. It was also quite warm out so that could have contributed to it.

 

Why pump up the tires to 40?

 

^less sidewall flex. Plus they can always be aired down if you feel the need.

 

Stockish, these things understeer at the limit. They are pretty well balanced and will spin on you if you do something dumb, but they love to push a few inches on turn in.

jfpimp is right on the air pressure

 

his fronts are 215s his rears 255s, pump up rear psi to compensate for the front understeer. More psi=less grip

I would have it at 37psi front and
45psi rear, and set your rear spring medium and front medium stiff with front and rear sway bars on.

If the car decides to oversteer abit too much, lower the psi in the rear and set the rear springs a few clicks softer..

and probably -3camber front and 0 camber rear....

idk thats how I like my setup

 

Max tire width in STS is 225... but you may have already found that out, or be finding it out right now. Best of luck.

 

Did you go? Was it fun?

 

Wich wheels did you decide to go with ?

I would of used the vert wheels, there excellent for autoxing or track days, nice and light.

I find a NA FC with 17s and a wide rear tire LOOKS awesome, but makes it VERY slow.

if your serious about your lapping or making the NA fun get some nice tires on the verts.

the Ventus RS2s in a 225 - 50 15 or even in a 205 50 15 all around and you will have LOTS of predictable grip

 

i wouln run the ssr. when i first started to autox my 88 z24 with the stock 215/50/14 i had major problms with sidewall flex on the fronts, it was running on the sidewall throu some cornners even with 50psi. i have ssr comp now 215/45/16 and i can beat the miatas in sts. all you need to do is get some better tires on your ssr, something with 200 treadwear or less, 225 all around, and you will be set

 

i ended up not running.. im going to wait untill i get some nice tires for the vert wheels...

 

Just run it. Autocross is not really that hard on the car and it's quick, cheap seat time. Don't worry about being competitive either. There will be plenty of people faster, and plenty of people slower, even at your first event.