Si wheel/tire size for G (H?) Street SCCA autocross?

[conehuntersi]

New member here, just picked up a new Si and looking to get some wheels during black friday sales to put a set of race tires on. I know these cars are pretty quick around the cones but I don't have much knowledge of FWD platforms, I've been racing in CAMC for the last few years. My question is what is the best size of wheel for street class, 17x8 or 18x8? 17s seem lighter and cheaper for wheels and tires, but there's no tall 200tw options on tirerack. 18s are a little heavier but can run a 245/40 or even 255/40 for longer gears. Any input from folks who have been autocrossing these platforms for a while? Thanks!

Sponsored

 

[AZCWTypeR]

Check the rules for the class you want to run. It used to be the stock classes had to run tires and wheels close to OEM diameter, width, and offset.

 

[86salmon]

As mentioned, you should look up the rules for the class you want to race. I believe max width for GST is 9"

18x9 +45 was the spec Tipple used to run with his FC1 at nationals on 265/35 tires


For street I believe you can change diameter by an inch and offset by +/- 7mm, however width is factory. Downsizing to 17 will make stickier tires more affordable


Here's the "unofficial class picker" from SCCA. https://www.scca-classifier.com/a/index.html

 

[conehuntersi]

Yeah my plan is to run street class for a little while (hopefully the Si gets moved down to HS with the GTI), so my options are 17x8 or 18x8. Looks like 18s are the way to go

 

[sackofcheese]

I ran a 18x8 + 45 with a 245/40/18 but was going up to a 255 the following season if my Si wasn't a lemon. The short gearing kills these cars if you have large courses, luckily for me my region only has super tiny lots, so I'd just bounce of the limiter. Using 18s gave me an extra MPH or two.

 

[conehuntersi]

Yeah we have a super large site, I've hit 70+ on a few courses in a muscle car lol. Got some 18s on order to help out on speed as much as I can, there's cars running top 5 pax with 52mph second gears so hoping I'm not too limited

 

[SlowAP2]

Yeah we have a super large site, I've hit 70+ on a few courses in a muscle car lol. Got some 18s on order to help out on speed as much as I can, there's cars running top 5 pax with 52mph second gears so hoping I'm not too limited

Just do 17X8+45 wheels and a 255 tire. Embrace the shift to 3rd. (I assume the big site you're talking about is GCAC). I use to tap the limiter in 3rd there on some courses with my old 19 SI LOL

Sponsored