rbauhart

Has anyone run a 295/35ZR17 and 245/40ZR17 Hoosier R6 combo on 10x17" and 8.5x17" wheels on a 964 narrow body? I have an RS America track car and some new Fikse's in these sizes, and am trying to run as wide as possible.

I know that 275's for the rear are common, but there is quite a large outside diameter difference between the 245/40 and 275/40 front/rear tires, and it's slightly less with the 295/35 rears. The overall section width between the 275's and 295's is only 0.6" according to Tirerack specs. Going to the 245/45 fronts will most likely be much too tall, as I have run 235/45 Yokohama A048's in this size and they have rubbed a little. My fenders are all rolled very well.

Any input would be appreciated.

Thanks,

Roland

LPM911

what are the offsets on the fikses?

i've been running 245 fronts on the 993 cup (cup 2) in 17x7 et 55 for last years race season with no issues.

joey bagadonuts

I'd solve the clearance issue by adjusting the ride height and adding negative camber. I've seen some 964's using 285 18's BUT these are fully-prepped race cars with 1,000-lb springs, monoball bushings, ERP spring plates, etc. 275's are already a tight fit, so unless you have a prepped track car, I'd steer clear of the 295's.

rbauhart

Thanks for the input guys. My Fikses are 8.5x17" with 51mm offset and 10x17" with 51mm offset.

I car is lowered with JRZ single adjustable suspension (probably going to Moton clubsports later this year), rolled fenders and the oil line in the rear fender well has been pinched and covered with a steel plate, I believe. I'd have to look at my spring rates, but I have tarett camber plates. Not sure on my exact camber angles, but there is a good amount of negative camber. I still street the car, but it's a track setup. What do you guys think?

From what I have read, I am thinking that if I put a 5mm spacer for a 46mm offset, that would probably be right about bang on and I should be able to squeeze 295's in there. I am trying a set of 275's to start the season with first, then might try one set of 295's and see if I encounter any problems. I just don't want to damage the car with any rubbing issues.

Roland

joey bagadonuts

I think the bottom line is whether the 275's perform well at the track. If your car feels balanced (no excessive understeer/oversteer) and tire temps are sufficient to extract maximum grip, then I would not make a change. If your car oversteers or the rears overheat, however, then a wider rear might be beneficial. A pyrometer would be helpful in making this determination.

As for the height issue, keep in mind that the 295's will only provide an additional 0.1" of vertical clearance while adding 0.6" of width. According to TireRack, the OD for the 275 is 25.5", while the 295 is 25.3". That's a 0.2" difference BUT you'll only get 0.1" of relief from the wheel well. The other 0.1" comes off the bottom.

Finally, if you do move forward, you'll want to measure the current clearance between the fender and sidewall. With 295's you'll be adding 0.3" of tire (per side) and then another 0.2" with the 5mm spacer, for a total of 0.5". If you can barely stick a finger between the tire and fender, then pushing the sidewall out an additional 0.5" will probably be problematic.

I'd also try to measure the clearance under load. Have a good friend stand on the threshold and jump up and down (seriously) while you insert a "feeler" of some sort between the fender and wheel to determine clearance. Something flexible (rubber maybe) that will give in the event it's squeezed between the fender and tire.

Sorry it's not more straightforward. The only definitive answer is for you to mount the larger tires and spacers and run them on the track. Trying to replicate track conditions, however, is the best predictor if you're not able to take your car in for a proper ride height and camber adjustment.

rbauhart

Thanks very much for all the input. I've decided to go with the 275's for now. See how they feel/handle/grip/fit. It's a good setup that I know will work and won't damage the car, and might be plenty of grip anyway, without the larger tire size. Might try the 295's down the road, but best to see if it is even necessary first.

Roland

joey bagadonuts

Agree!