Widest tire on 17x7?
 

Thinking about new wheels, some with a 50mm offest and others with a 42.

What's the widest tire I can fit on stock suspension? I'm thinking 235/40, even 245/40 if it fits. Probably Dunlop ZII's or Bridgestone RE-11s.

These will be for autox only.

People in CS have done 245s

Correct. IIRC the Hoosier 245 needs the +42 offset but the street tire 245s can live on stock offset. +50 might be pushing it though. Regardless, why not maximize your track width?

Tire manufacturers recommend 215 maximum for 7" wheel and 245 maximum for 8"

An extremely stiff tire like the Z2 can do 235 or 245 on the 7". Something softer like an RS3 or any normal street tire (not competition level), I would stay with a 215.

Ive been running 235 Z2s, 215 RS3s and 215 daily tires for a while. I have effective offset of +47 and I can clear 245s on them (+50 with 3mm spacer). 245s will work on the Z2s, a few people are doing it but most are going 235s

I have 245/40 hoosiers on mine. My wheels are +42, and sitting in grid I can just squeeze a finger tip between the tire and the spring. Even on A6s, I think once you pass 235, you start getting diminishing returns. That is, the 245 puts down a bigger contact patch than a 235 will, but not the full extra 10mm.

When I go to street tires next season, I'll probably be on some flavor of 235.

With the right equipment, I've seen 275s on a 6" rim.

I know everyone runs RPF1s but what about Kosei K1 TS? The OZ wheels are just too expensive but the K1s are even cheaper and lighter than the RPF1s.

I run them, with a 3mm spacer.

I'm using a 245/40 RS3 Version 2 on RPF1s for CS. No problems so far.

I run the Kosei's, but I am using 225 tires. For me it's a cleaner fit and I can run the rears at lower pressures and the stay responsive and don't roll over. I think the majority run 235 though, which should still fit on the Kosei's, but I'd guess it would be close. 245 on the Kosei would definitely require a spacer.

225 is the widest I would go.

I run 225 Yokohamas which are wider than most/all other manufacturers in that size on Koseis +50. They fit fine, but I run a 5mm spacer now for peace of mind. I'll probably run 245 or 235 next.

You sound like the robotic dude who refused to mount my 245's on 17x7's at Discount tire.

"The tire could fall off the rim and cause a serious accident!"

245's fit just fine on a 17x7 in the rear, and I haven't died yet.
Pictures here:
http://www.ft86club.com/forums/showt...t=41955&page=2

Domo arigato Mr. Roboto.