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[irex511]

Hey Folks,

I just ordered a new set of wheels for track and autocross and am looking to figure out the widest tire I can get up front. Due to SCCA classing rules, I had to keep offsets within close range, so my Forgestars are F: 18x9et31, R: 18x10et25 (Competition Package).

Obviously for grip reasons, I'm looking to go for BFGoodrich RivalS's or Potenza Re71rs.

Given that they'll be on 18's, do you think I'll have any trouble getting the 275/35/18 on the 9" front (this is the same tire I plan to run in the rear unless a 285 will fit)? I know the 71's "like" to be pinched a bit but just want to make sure I wont be rubbing too much? If it's a better fit, I could also bump down to the 265/35/18's or the 255/35/18's.

Size 1 Size 2
Diameter
26" (255/35/19)

25.6" (275/35/18)

-1.5%

Width
10" (255/35/19)

10.8" (275/35/18)

+8%

Sidewall
3.5" (255/35/19)

3.8" (275/35/18)

+8.6%

Circum.
81.7" (255/35/19)

80.3" (275/35/18)

-1.5%




If anyone knows what the other FS guys are running for SCCA, that would be greatly appreciated. (I debated whether to post this in "track and autocross" or "wheels and tires").

Thanks so much for the help!

[AP3X_FTW]

Obviously slightly wider wheel widths would be preferred, but with due to class rules I understand why you had to stick with those sizes.

In terms of tires, you could run any of the following configurations without rubbing:

* Preferred for your wheel widths
Front: 265/35-18
Rear: 275/35-18

Front: 265/35-18
Rear: 285/35-18

Front: 275/35-18
Rear: 285/35-18

[CSBM5]

I've had no problems with 275/35-18 Rivals all around on nonZCP car hence used 8.5 ET26 and 9.5 ET17. Stock offsets are 29 and 23 for the nonZCP wheels. The 275 Rival on the 8.5" front wheel worked fine with only a bit of sloppiness in transitions compared to a 245/40 I had also tried. Edge wear was very good too.

I would mount the 275 on the 9.0 ET31 wheel and check for tire to strut clearance, especially with the Rival, but that would be the only area of concern.

[dab_of_oppo]

I'm in the middle of the exact same decision. Thanks to those who've replied !

[Richbot]

Yes.

Although if it were me, I'd try the 285/30-18 RE71R square. Worth it IMO for the gearing advantage out back and the extra tire up front. The 285 wasn't available when the car won last year. If you have to run a small 3-5mm spacer to clear the front strut (I don't think you would, the 295/30-18 Hoosier fits up there at stock offsets on an 8.5" wheel) it's a win/win, more front track = more front grip. The RE71R is such a stiff tire that over-tiring it doesn't seem to have many downsides on a heavy no-camber car like ours that punishes tires. Considering the tire size arms race the M3 faces, the 285 makes a lot of sense especially because it's on the narrow side of cars in the class but can still fit one of the widest tires under the frontend now that there is a good short-wide option in the 285/30. But bring your tire guy a six-pack or something to say sorry