Cannock

It is time for a new set of rear tires. I currently have 225's on the front and 255/40 on the rear. What I am wondering is can I go with 265/40's for the rear? If I do, do they have the same rolling radius?

Thanks

DJF1

Proly not. the 265 should be taller than the 255. With 225's in the front and 255's in the rear its a good setup for less understeer. My suggestion is to keep it this way.

STLPCA

What Danny said, assuming you care most about balanced handling. However, if you have other priorities, the increase in diameter will only be 0.3" +/- which should not cause any issues (unless maybe if your car is lowered a bunch). The larger rears will result in about a 1.5% F-R diameter difference which is not enough to cause ABS problems. The rake will change slightly & your speedo may be low by 1 mph @ 65. Otherwise, should work fine, albeit w/more understeer than you now have.

Bill Verburg

Well the Carrera RS used 225/40 & 265/35 in 18s of course, but the priciple is the same.

You might want to think about 235/45 & 265/40

you will find that the slr(static loaded radius) and rpm(tire revs/mile) are much better indicators of changed gearing and/or speedo readings. The 265/40 is really not much larger(in general) than a 255/40 ~.1" in this area but there is a lot of variation in actual vs nominal specs from the various manufacturers

Cannock

Thanks guys, my car does have the PSS9 kit on it. It is lower by about 1". I think I might stick with the standard tire for the street and get a different set of rims for the track. I am considering 18's for the track which I assume I can then use the 265/35's. Anyone have any 18" 8's and 10's for sale?

Martin S.

I run 235/45/17 fronts on 7" wheels and 275/40/17 rears on 9" wheels, all mounted up on standard Cup wheels. The Tires are Toyo RA-1. This combo works perfectly, andf the rolling radius is < than 1.5%, no ABS issues. I calculated this on an EXCEL spread sheet that all can have if they send me a PM with an e-mail address. If it were a perfect world, I would have 8" wheels on the front, and 10" wheels on the rear...I just didn't want to spend $3,000 on a set of custom wheels for the track.

Note I also drive these tires on the street...they are very quiet compared tpo my formar Kumho Ecsta MX tires.