Has anyone here run 285s on rear of a C4S or TT?

The reason I ask is that there seem to be a lot more options in that size and I wonder if perhaps it makes little difference. I've read on this forum that Porsche in this case selected the best sizes in the first place, but I'm just curious if anyone tried 285/225 setup. For example, In 285/225 the options are: BFG K/D TA $914 Bridge. S02 $956 S02A $924 S03 $902 Conti 2s $840 Dunlop 990 $908 Mich PS Rib $980 Pzero Sys As $936 Pzero Rosso $924 Also, for track tires, Hoosier RS303 $988 Kumho V700 $842 Mich PSC $1172 Pirelli Corsa $1170 Yoko A048 $1176 for 295/225, the options are: Bridge. S02A $944 Conti 2 $860 Mich PS 2 $1172 Pzero Sys As $914 Yoko AVS $856 Track tires: Mich PSC $1258 Pirelli Corsa $1214 I'm not saying we don't have enough options in 295, but there certainly are more options with 285s...

Yes, but only if I have no other reasonable choice, such as for track tires. The rolling circumference between the 295 and 285 is so small, PSM/ABS or the VC won't know the diff.

True, there would be a .946% difference so it wouldn't pick it up. I guess my question is more with reference to grip... Considering that the C2's run 285s, I don't really see why they put 295s on the c4s in the first place. The additional weight is in the front (at least added mechanical weight). Perhaps the wide body adds a little weight in rear but I doubt that would provoke the additional tire width.

In real life, I don't think there will be a noticeable diff. Especially if you're talking about street tires for street use. I can't really say from experience, since the 285's I use are R compounds while the 295's are street tires. As I know you've raced before, the better forum for you to ask this question may be at the Perf. and Comp. section of Rennlist.

I dont see any problem running the 285, but I think the rear tire might look a little small if your car is not lowered. I know the difference in height is small but on these low profile tire every mm counts.

They did it for looks, and to fill those fatter rear fenders. You will never notice any difference between the 285 and 295 on a C4S. Mainly, because you'll never reach the grip limits of the 285's. If you decide to use a 285 tire in the rear, Porsche has a matching Turbo Look II wheel in 10" that would work great. I would probably use a 5 mm spacer with it. 996.362.140.01 - 10" x 18" - ET47

Viken, Are you saying that he can't reach the limit of grip? I know I have with my C4S on the track. I agree that most drivers would never walk the fine line of adhesion difference between 285 and 295's, but there is a difference so it may matter to some people.

ghost do you think there's really a measurable difference between the 285 and 295 if our friend palting hasn't found it on the track? as for finding the limits of adhesion, i agree its findable on a really tight curve if you're cookin'. i do doubt that there is any real differences between 285 and 295. heck even the winter tires do a pretty good job holding a curve with 265's

Ken, Yes, of course it is possible to unhook a 295 on a track given a competent driver. However, for us mortals to do so, we'd have to make a bad move to get any of the four tires on a modern day AWD Porsche to lose grip. As such, I think the same applies to either a 285 or a 295. There is also the differences in rubber compound and tire construction between manufacturers. I'll bet a 285/30 P-Zero Asimmetrico will stick ten times better than a 295/30 S-03.

I had no idea that 4 wheel drifting in a C4S was so hard, it could be that our local track has just the right turn for it because it is one of my favorite things to do around a particular turn. I need to mount a camera and catch it on video sometime. I am in total agreement that the adhesion difference between the 285 and 295 will be slight and that brands may indeed have a greater difference than simply the size. Given the same brand though, it would be interesting to see in terms of G load and mph what the actual difference is assuming that all other factors are the same (car, temperature, wear, etc.) Those prone to doing physics calculations could probably tell us the theoretical adhesion difference of the size difference alone, but it has been awhile since I had to do calculations like that and I never enjoyed them then and wouldn't now. You know I might add that driving the C4S in the snow and getting familiar with when/how the PSM kicks in makes good practice for understanding what it is going to do on the track if you leave it on, which I normally do.