cgfen

Looking for input for appropriates sizes for new tire purchase.

Car = 96 C4S no mod’s.

Current tire sizes =
225 – 40 X 18 = F on 8” wheels
285 – 30 X 18 = R on 10” wheels

Car has obvious oversteer currently. I know that C4s tend to oversteer anyway do to extra mass up front, but I feel it even more since the tires are original 1996 oem with 19,000 miles.

If buying tires to work towards neutral handling with no other mods, what do you recommend as new tire sizes?

I was thinking of
235 – 40 X 18
And
265 – 35 X 18
On stock wheels if I can find proper diameters to keep AWD happy
I’m pretty sure that most 265 – 30 X 18’s are too short to keep AWD happy.

This will be a wheelset used for AX / DE / Track fun.

Thanks

Craig

Rich Sandor

Actually, the consensus is the opposite. A C4S will understeer in comparison to a C2S. Mass up front, and front wheel drive, actually contributes to understeer, not oversteer.

I would NOT downsize the rear tires. You will need more rubber to provide traction for the rear tires under accelleration and cornering. Putting 265's is only going to make the rear much more difficult to control. Conversely, going to a 315 series will give you significantly more traction, but will also take much longer to warm up during a run.

cgfen

[QUOTE=Rich Sandor;4627101]Actually, the consensus is the opposite. A C4S will understeer in comparison to a C2S. Mass up front, and front wheel drive, actually contributes to understeer, not oversteer.

You are absolutely right.
my brain was thinking understeer, but fingers typed oversteer.

Thanks for the input.

Craig

Wilder

I agree with Rich and would suggest you consider 235/295 as a good compromise. You can mount them on your stock 8/10" rims. If you want to dial out the understeer and make the car more neutral, you may want to consider going with ~ -.25 more camber in the front that the rear. It's worked great for me. I don't know what tire brands you're looking at but Falken Azenis 615s have worked great for street/AX on my C4S.

Check out this thread: https://rennlist.com/forums/autocross/363027-good-discussion-on-wheels-tires-and-other-performance-mods-great-for-newbs.html

cgfen

thanks for the comments
i was pretty much going down the path of the Falken 615s due to your thread with Ted (Drcar).
but
235 - 40 X 18 = 25.5" OD
295 - 40 X 18 = 27.2" OD
according to Falken web site

http://www.falkentire.com/rt615_sizes.html

that seems like to much delta to keep the AWD happy.
Are you using different sizing?


they also list
275 - 35 X 18 = 25.6" OD, not as wide, but shorter

thanks
Craig

Wilder

Glad you cought that. Yes, Falken sizing is a problem.

I've got 9" and 11" rims so I went with 245s and 315s. I'd like to try smaller sizes as 245/315 are too heavy and the width might be slowing me down. I most likely will go down to 235s and 275s for my next purchase.

BTW, I saw the pics of your car on the other forum. Awesome color.

Dr. Car

I think that 295/30 rear and 235/40 front Yokohama Advan AD-07 on some 11" and 8.5" rims would be ideal. Those tires are pretty much worth the big money that Yokohama charges for them. I don't know if the Volk TE37 Porsche is made in the right offset, but your 4S car has so much clearance it would probably work. The Volks are really light - although expensive, and you may or may not like the Euro/JDM contrast.

Wilder

Volk TE37s do come in WB offsets and in 11", 8.5" and 9" widths.

Paul E. Dodd

Craig,

I've had good luck with 245/35-18 up front and 285/30-18 at the back in my 993 C4S set up for SCCA A-Stock class autocrossing. These fit on stock 8"/10" turbo twists. I use a 5-mm spacer and -1.9 degrees camber in the front to prevent rubbing (mostly). I still get a slight rub on the inside front wheel well, but I got that even with 235/40-18 MPSC's. Both Kumho V710's and Hoosier A6/R6 are available in the 245/35 and 285/30 combo. I think that's the sizing that Paul Kozlak successfully used to win the SCCA Solo Nationals championship in A-stock in 2005 in his 993 C2.

I'm using the 235/295 (996 GT3 size) combo on the street and like it a lot. I'm currently running Kumho Ecsta SPT's in that size on another pair of stock 8"/10" twists. These tires are remarkably good and very cheap. Surprisingly, my datalogger showed that these tires were within 0.1-0.2g of the grip of the V710's at a recent autocross school.

The Volks are really nice (though unfortunately not legal for me since they don't make them in stock widths), but if you're relatively new at this, the standard twists should be sufficient for now.

Good luck with your choice and have some fun out there!

Paul

FlyYellow

go with 245/35/18 up front and 295/30/18 in rears... that will be a nice setup for your car.

cgfen

Thanks for all the input

for now i used the 996 TT HollowSpokes as my "track" wheels.
I bought Goodrich KDW's
235 - 40 X 18
295 - 35 X 18

initial impressions;
1. whoa, those rear tires are tall, nearly an inch taller than stock 285 - 30 X 18, no rubbing, but even higher gearing
2. still have mold release on tires so too early to tell about grip.

Also have stock 18" Technology wheels, might use these for track wheels instead and go with
Falken Azenis 615s
235 - 40 X 18
275 - 35 X 18

Yes, i'm just learning.
will report on impressions as time goes on

Weight data points
996 TT 11" wheel with 295 - 35 X 18 Goodrich KDW = 57 pounds
996 TT 8" wheel with 235 - 40 X 18 Goodrich KDW = 46 pounds

wasn't smart enough to weigh wheels / tires separately.

cheers

Craig