donuts

Hi, I have a 996 C2. I know this proposed setup is not the best but I was wondering how I can make the most of it. I can get a free set of 17" Boxter wheels 7" and 8.5" wide. I'm not sure of the offset. What is the best tire size to go with? I want to run an R compound for mostly auto-x, but I don't want to run autox compound because I want to drive to the event and possibly run a few track days. I guess this would mean RA1's? Will this rim width work or am I asking for too much with these narrow rims?

Joe Weinstein

If you can be sure to avoid water, you can track and drive on Kumho 710s, and
do very well. Otherwise street tires are the way to go. The Yokohama AD07s
are also good.
You have to find out whether those wheels have an acceptable offset for
your car. Assuming they do, just look at the specs for the tires you are interested
in, and choose the size tire that the manufacturer says is correct for the rim width.
Joe

Jim Michaels

donuts: I'm hoping you'll decide not to try to make the most out of the 7 & 8.5X17" Boxster wheels. Even with R compound rubber, I don't think you'll be able to get them to work as well as your OEM wheels with good road tires. Some things that are free are just not worth the price.

racer

Base OEM 996 c2 rims are what, 7.5 and 9 x 17? 7 and 9 x 17? If so, you won't be giving up too much since you could squeeze on the same size tires. A 225 front and 255 rear would work. You don't state how much experience you have re: AX and DE.

RA-1s are good compromise tire. I haven't run the V710s but they are great AX tires. I liked the Victoracers too. Not sure who makes which sizes these days.

donuts

Jim, that's what I was wondering. Will I be able to get wide enough tires on the boxter rims? What is considered the ideal size, front and rear?

Joe Weinstein

for autocross, you want as wide as you can fit (wheels and tires). For a given
wheel, go with what the tire manufacturer recommends for the rim size. Eg:
for an 8" rim, it is sometimes better for stick to run a 225 whos maximum is an
8" rim, than to run a 245 that has 8" as it's very minimum rim.

Jim Michaels

donuts: I'm not sure what the ideal sizes would be, but I think the 996 went to 8 & 10X18" OEM wheels in 2002. Thus, those Boxster wheels are narrower front and rear than stock; plus they have different offsets, which would mean using spacers to get the right fit. Then the spacers would force you to get longer wheel bolts to ensure proper thread engagement. Even after getting them spaced properly with sufficient thread engagement, however, you'd still be stuck with the narrow rims, forcing you to mount tires that are also significantly narrower than you'd like to use for autocross and track. You might like your car better in the snow like that though.

Dr. Car

The Toyo RA-1 is the favorite for the part-street, mostly track driver. However, the Kumho "Victoracer V700" (not the plain V700) fits the bill and is a lot stickier. I recommend that on those size rims you run the Victoracer in 225/45/17 front and 255/40/17 rear. I've run those very tires on those same size wheels on a Boxster, on the street and the track.

The Victoracer should be heat cycled, either by the tire seller or by you before you hit the track.

Dr. Car

Do you have objective data to back this up?

I disagree. Lots of top SCCA autocrossers consistently cram big tires on rims that are less than the manufacturer's recommended rim width. It is a hassle for the installer, however.

Dr. Car

Here too I disagree. 17" was the base wheel size on the 996 for most or all its years, and widths for the 17's were close to that Boxster 17" size, probably only a 1/2" wider for the rear rims, with OEM tires sizes of 205/50/17 and 255/40/17. I'm sure that was standard on the 993, and 964's that were optioned up to 17's.

The 17" diameter does not suffer in performance compared to 18" tires. The sidewall is sufficiently short for good performance and width of the tire will have the real impact on performance. Unsprung weight of a 17" wheel and tire combo is a little less, and tire replacement cost is lower. I am positive that even with a lot less rear tire, a 225/45/17 & 255/40/17 Victoracer combo will outgrip street tires in 225/40/18 (same stated width) & 285/30/18. 225/255 will provide a nice front-rear handling balance, even if the OEM size spread was 205/255. I like the idea of going up a bit on the front tire widths because stock 996 cars tend to push. So in an 18" tire combo I'd squeeze a 245/40 or 245/35/18 on an 8" front rim.

I second the concern about whether the Boxster offsets are correct. Just make sure if you haven't already. That said, a free or cheap set of track wheels is a great thing. I take it that you don't want to molest your OEM wheels and street tires, and you want a second set to go play with. You have the right idea.

Don't run the Kumho V710 on the street unless you're going very short distances and you know you won't have rain on the street or the track. I only recommend that tire for dedicated enthusiasts who bring a set of r-comps to mount at the track or who trailer their car.

Donut man, please get a good track alignment done. I recommend up to two degrees negative camber front and 2.5 degrees rear. Even toe front and a small toe-in for the rear. Ask around with other 996 track users. The negative camber will increase your grip and tire life on the track. Depending on your driving habits, the camber will either even out your street wear or make your insides wear out faster.

- Ted

Joe Weinstein

As you wish. You may be right.

Joe Weinstein

http://www.sfrscca.com/solo2/Results...nship/asp.html
http://www.sfrscca.com/solo2/Results...onship/t2.html

Grantsfo

The new Nitto NT01 would be ideal for your application. While I havent driven these tires I have seen them perform on other cars. I used to run 225/45/17 and 255/40/17 tires on those same rims when I had my Boxster. Those sizes worked great! The Nittos come in those sizes. And even wider.

Wonder if you could stuff 245/40/17 on fronts and 275/40/17's on rears and get similar or better performance?

Dr. Car

I am sure they could be mounted on the 7's & 8's, as I've run 255/40/17 Victoracers on 7" and 275/40/17 V700 on 8". I once ran Nittos NT01s on a Camaro - I thought they were an excellent street/track tire, though not as grippy as the Victoracers or Hoosiers that I also ran on the Camaro.

Irksome

Untrue. From 1999 to 2001 I believe you are correct, but in 2002, the 996 went to 18x8 and 18x10. The stock rear tire was 285. I am not certain on the stock front tire width, but I THINK it was 225. I can check when I go out to my car in a few minutes. This was a big topic for me last week as the local PCA tech inspection chart had the wrong width tires listed for the 996 and 997, and I had to get a clarification to determine if I was in street stock or stock.

I know this because I am trying to find some track wheels and tires myself, and I am struggling to find what I want. My street (and only) wheels are 997 takeoffs, 19x8 and 19x11, and I'm taking 2 points for my 295/30 rears. In the ideal world, I'd be able to find some 17x8 and 17x10 wheels, and put on 235 fronts and 285 rears, with decent tires. I'd rather take the points for better tires than the extra 10 cm on the rear width, especially since I have definite understeer, and have a very very hard time pitching the car.

I haven't yet found the wheels. If anyone has any recommendations for that I'd love to hear it!

Dr. Car

Irksome, are you running OSS or OS? And what kind of tire do you want to run - street or R comp? Do you want to run your a/x & d/e tires on the street, or will this be a separate set of wheels altogether? Whether you get 17" or 18" may depend upon whether your ideal tire model and size is made in one diameter or the other.

To help with understeer, I'd recommend going wider on the front wheel and tire. Instead of a 225 or 235, get a 245 or 255 for the front. Instead of an 8" front wheel, go with a 9". Although a 245 is commonly squeezed on an 8", a wider wheel plans a much larger patch of tire on the ground. When you go wider on the front wheel & tire, you'll have to be careful about offset/spacing, to avoid rubbing. A custom set of one-piece forged CCW C14 wheels in 18x9 and 18x11 with 245/40 or 245/35 front and 285/30 rear (if allowed) would be a dream. Those wheels are VERY light and the wider front tire would help with understeer.

Another solution to increase front end traction might be increasing your front track with spacers. IIRC, there are no points for spacers in local rules.

And, do you have a good alignment done, with max front camber and care taken to set the front/rear toe to recommended track specs? Talk to Mirage International about alignment and solutions for understeer. Mirage is located in Rose Canyon near the I-5 and Hwy 52. Jae at Mirage has forgotten more about this stuff than I'll ever know.

In the meantime, see what overinflating (another 5 psi...) your rear tires will do. Might reduce traction in the rear and aid rotation. Of course, balancing a car by robbing one axle of traction is always a crude and suboptimal solution.

Enjoy!