Best wheel size and offset for autocross?

[Knox Joe]

I'm going to be going with coilovers and smaller rims/tires for next years autocross season. Just wondering if you guys found what works best.

I am currently on stock Tokico's, Espelir springs, and 18x7.5 +38 Enkie Evo's, on 225/40/18 Hankook RS2s. Will be going with BC coilovers with custom spring rates, probably 8k F/ 6k R, and I am looking at going down to 17's, because it rubs pretty bad right now with a heavy load on the suspension. Thinking about running Rota Slipstreams in 17x7.5. Tires will most likely be Hankook RS3s.

I'm just confused on the offset and what will let me run the widest, fattest rubber.

 

[CulRidr]

Any reason why you want to keep with such a big tire? 15" will fit over MSP brakes, are lighter, cheaper and offer more (much cheaper) tire options. Others can come and chime in on the best offset/width specs

 

[Knox Joe]

I guess I should have said this in my OP; I have a lot of problems putting power down. It smokes the tires all over the place. Going with a 16 or 15 is only going exacerbate the problem.

 

[CulRidr]

RS3s are MUCH grippier then RS2s... so that should help a lot. Are you having issues everywhere or just at launch?
And that much WHP on such little boost? Nice!!

 

[Knox Joe]

Yeah, everywhere. Exiting corners, straights, launch, all the above, lol.

Oh, and I have a lot of supporting mods.

 

[thecrash91]

what mods do you have? i have a hard time believing stock psi with stock turbo can make that much WHP, not trying to sound dickish or anything. have you gotten it dynoed?

 

[HighSpeed]

I have never seen slips on an MSP, but they are a good compromise of size and weight.

 

[Knox Joe]

Has anyone ran 225/50/16? I'm liking this look, and I can get RS3's in that size. The RS3's only other size that would fit the MSP would be 225/45/17.

 

[CulRidr]

The 225-45-15 would work as well

 

[rally2003]

Has anyone ran 225/50/16? I'm liking this look, and I can get RS3's in that size. The RS3's only other size that would fit the MSP would be 225/45/17.

These are the tires I'm getting next year. Should fit with a offset around 50+ I was going to get a set of 16 inch Kosei rims that weigh 16lbs and that same tire combo. I should be killer in STU next year. Coilovers with camber will help with the traction problem. I had Ksports on for 2 weeks and the difference was crazy, but they are racing coilovers. I'm thinking about getting rid of them cause I have to drive mine daily about 60-70 miles a day. I had Enkei Evo 5's 17" back in the day and they rubbed in the rear like mad too.

 

[Knox Joe]

So how low an offset could I run with 15x7's? I was thinking about running 15x7 +35 w/ 225/20/15's. Shouldn't rub the fender with that small of a tire, or at least I wouldn't think so.

edit: Oh, the reason for asking is I believe I'm going to go ahead and switch to r-comps.

 

[CulRidr]

Are you bound to a specific class? Do you want to stay within the fender or do you care if you stick out?

 

[Knox Joe]

Are you bound to a specific class? Do you want to stay within the fender or do you care if you stick out?

No, SM is pretty wide open. Don't mind a little poke.

 

[Knox Joe]

Okay, so I am ready to buy wheels (read: permission from wife), and just don't know what to get. Will be running 205/50/15 takeoffs, so probably go with a 15x7, but still undecided on offset. Also, are we sure there is no possibility of the caliper not clearing? And, what about hub bore? The MSP is 71.5 correct? So I'd need a 71.5 or higher bore, and if it is higher than 71.5 I will need hubcentric rings? Is this correct?

 

[CulRidr]

centre bore is 67.1 AFAIK, and a 15" clears, but just barely. Go for a ~ +45 offset as you'll get wider track without having to deal with rubbing issues.
here are my 15*7, 67.1CB, +45 offset wheels with MSP calipers using 195/50r15 RE-01Rs...

 

[Knox Joe]

I thought the higher offset would pull the wheel in towards the strut... I run a +38 on my 18x7.5 Enkei Evo 5 wheels.

I am looking at Roat Slipstreams 15x7, +40, maybe in black, even though I really don't like black wheels, but these are for autocross duty only

 

[CulRidr]

You are right, sorry, I was comparing to stock offset; forgot that you were running +38 on your aftermarket ones.
+40 should be OK if the coilovers are stiff and you are running a good amount of camber.

 

[Knox Joe]

Ended up buying 5Zigen FN01R-C, 15x7, 5x114.3, +42 in bronze. $560 out the door at discounttire.com.

 

[daonly1around]

if your going with 16's you should look into the FD rims. 16x8 and very light weight

 

[Knox Joe]

Already bought the 5-Zigen wheels. Had to stay with 15's because I have a connect on slightly used take-offs in r-comps, and they mostly come off Spec Miatas in 205/50/15. Going to be running race tires next season.