No HTwo O

I plan to get a second set of wheels and tires for the 993. I am going to do the Yoko AD08.

Wheels are stock 996 hollow twists. Rears will be 295/30/18 for sure. I have questions about the fronts.

Since the fronts are an 8.0" wheel (rears are 11") can I still go with the up size 235/40/18 tire? Or should I stay with the OEM 225/40/18 tire?

Right now I have the 235/40 and 295/30 set-up, and love it, but my current Speedlines are 8.5" up front.

So, the question is, is an 8.0" wheel to narrow for the 235/40/18 tire?

Thanks.

Falcondrivr

I run 245/18 R6s on 8x18 my02s on the track and they run fine.

Bill Verburg

Choosing tires is a balancing game, one limiting parameter is wheel width, Y008 235/40x18 want a wheel 8 - 9.5" wide, you get the best performance from the 9.5 w/ least comfort and most comfort w/ least performance from the 8.

you also want to match f/r tire heights for best ABS performance 295/30 is a 25" tire, 235/40 is a 25.3" tire, while not a perfect match this is acceptable

Roche993

I run the exact sizes you are looking at on my 996 turbo rims and, to me, they work perfectly together on the track. So I dont think it is too narrow up front. Good luck.

certz

Bill - I run the 235/295 AD08 setup on the C2S and I do not have any issues. Cheryl and I autocross the car with this setup and it does pretty well. Bill V, as usual, makes very good points in regards to tire performance and how sizes can effect other aspects of the car - like the ABS. Of course, the TT is also AWD, but again I think the percentage difference in tire diameter is acceptable for this as well.

Bill Verburg

I never said or even intimated that there was a problem, I merely reiterated the fact that to extract the best performance from any tire you want to use the widest wheel that it is spec'ed for, to if you use the narrowest wheel that it is spec'd for then you will lose some performance and will get the most comfy ride from that tire.

This and cost are 2 of the main reasons oem's tend to spec narrow wheels

Another thing that I didn't mention is the oversteer/understeer question. I've found that you have to go to great lengths to increase front grip to reduce understeer to an acceptable level. changing tire and wheel widths and or o/s's also changes the over/under steer characteristic

Now each of us is likely to have a different definition of how much understeer is acceptable, it's just something to factor into these sorts of decisions

certz

Bill V - the Bill I meant at the beginning was the OP (I know him, he lives in Chicago also). I absolutely know what you meant as far as wheel widths and tire sizes go as I enjoy the numerous posts you have made about this subject. Your knowledge is invaluable as far as I am concerned and has helped me choose tires in the past.

The diameter difference is a common point in your responses, but in a recent thread you talked about using the narrowest tire recommended for a given rim width. I had not heard this before but it makes sense. I assume one of the compromises with a setup this way is the sidewall will be at its stiffest. Is there any other "negative" (negative is not the right word but I cannot think of a better way to put it), like is there a higher probability to lose the bead with this configuration, especially when driving aggressively. I ask this because I renecently had a set of 275's on the rear of the same rim the OP has (the 11" 996TT hollow spoke) and it looked really stretched.

cgfen

No
many of us use this combo.
Have fun.

Craig

No HTwo O

Thanks everyone.

Bill Verburg

that's just saying the same thing in a different way
use the widest wheel spec'd for a given tire

use the narrowest tire spec'd for a given wheel

yes, the idea is to stiffen the sidewall, if you look at the tires in professional road racing you will see the flanges of the wheel are further outboard than the shoulder of the tire...widest wheel for a given tire


The ride will be worse, the wheels will be more exposed to curb rash, the bead seal will be fine as long as pressures are nominal, but this is why you don't go beyond spec. 275/35 x18 is usually spec'd for a 9 to 11" wheel so your fine there. 295/30 x18 are usually spec'd for 10 to 11" wheel

No HTwo O

Thanks again, Bill!

Is this "difference" much different than the stock OEM sizes of 285/30/18 and 225/40/18??

JPP

I have the same setup on my new 996 TT Twists, Yoko AD08's and although I upgraded to 295's on the rears I kept the 225/40's on the fronts because they fit perfectly without stretching the sidewall too much.