I'm trying to spec out the appropriate wheel spacer for my autocross set-up and I was wondering how much wider a Hoosier A6 285 30 18 is than a Kumho v710 in the same size (so that I only have to buy spacers once)? I'm also considering shorter front springs for my Ohlins.

I ran my first event with FN01RCs +35s, 285 v710s, a 10mm spacer, and the camber bolt turned to the min setting (for tire clearance). I was limited to -3.0 camber on once side and about -3.3 on the other and it appears that the tires had some light contact with the springs.

I'd like to flip the camber bolt, which appears to take away about 7-8mm of tire clearance to the spring by itself, so I was leaning toward a 20mm spacer. Now I'm wondering if I need to go to a 25mm spacer in case I decide to run Hoosiers in the future. Hence, my question about the actual width of the Hoosier vs. Kumho.

Another alternative to narrow the spacer a bit is to run a 6" rather than 8" spring, but I'm not sure how to calculate whether I would run into a coil bind problem if I did that. I'd probably put a 12K spring in the front if I were buying new springs. Has anyone else run a 6" spring in that rate range without coilbind issues?

When I was ready for my first event on the new tires/suspension I thought I was done with all this fitment stuff, but I guess not.

Thanks!

 

A Hoosier is about .5-.6" wider secion width..so about 1/4" per side. Everything on my setup clears great except for the coilover spring. I run a 7mm spacer to clear the spring. I've also considered running a 6" front spring...but haven't made that jump yet. You'll have more fitment issues I'm sure once you run them hard a few times. I rubbed through on the front fender liner and beneath it is a sharp piece of body panel seem. It cut my tires slightly...so I had to hammer it in a little. I also had front fender clearance issues with the spacer so I had to roll the front fender lips up a little as well. Now everything seems to work great.

 

What offset are your wheels?

EDIT: I just did a search and saw that you have +24 Forgelines, so if you are running a 7mm spacer, that's effectively +17, which would be like a 18mm spacer on my setup. Hmm...

Thanks.

 

Yep +24 front +36 rear. I have a good bit of clearance now. I may even be able to flip the camber bolt back the other way if I wanted to. I also run -3 deg camber.

 

I run 6" free length H&R in 700lb (12.5K) and 5mm H&R spacers up front to clear my tires...it's been a year now. No coil bind issues. These springs have more space between coils than the longer ones. Plenty of room for compression.

FYI, the wheels are 18x9.5 +38 with Kumho MX 275/35-18's. And yes I had to flip the camber bolt for clearance.

Hope this helps.
Cheers!

 

Those springs with less coils may have more "room" to compress, but they don't really have more usable travel. That type of spring tends to permanently deform before even reaching it's block height. So it's important to check the specs before purchasing.

 

Thanks for the analysis. The point was that the travel was strut limited, not spring limited. These springs are not "specially manufactured to have more space between the coils" or "a special type of spring which increases travel". It was a simple observation in contrast to the springs that came on several sets of coilovers I've had.

I selected these because of the specs, and chose H&R due to their time-proven use in winning at the highest levels of professional motorsport. That is the "type of spring" worthy to be on my car.

Regards,
Ethan

 

+1 ... I heard the same thing too about 1/2" ... I have the pleasure of stacking up 245/45/17 R3 (R3 S03s I think) against some 245/45/17 RT-615s and the difference was profound. Cheating Hoosiers