AutoX924S

Hi. I am new to the forum and I have a 1988 Porsche 924S. Right now we stock everything (except front shocks which are KONI's) and 195/65/15 tires on our 15 x 6 stock PD rims. Me and my dad always have long arguments about the tire/wheel combinations. I want to settle this for good! My dad thinks that we cant fit 17" rims without sacrificing tire durability and the softer ride by getting lower profile tires. He thinks by getting lower profile tires it will "significantly" reduce the tire wear and make the car really stiff and uncomfortable to drive on the road. I tried to explain that when you lower the height (profile/series) of the tire, it doesnt make the tire thinner, but only makes the tires stiffer so they dont flex as much under aggressive cornering. Hey says, "Im sure making the tires lower will put more stress on the other parts of the tire and reduce the tire wear". He also thinks that no one uses lower profile tires for racing (45,40,35 series tires) because of the durability. Is this true? So basically what we want to know is what size tire would be most efficent for mosty AutoX/DE and sometimes being daily driver. Feel free to correct me on my mistakes or misunderstanding... im just trying to learn.

Thanks

Kevin Baker

Your best bet is to go with a 16x8 wheel. That car should accept a 215/50/16 with no problem. On my 86 n/a daily driver I have 15x7's with 205/50/15 in the front 225/50/15 rear.

If you are looking for a good tire....check your local Firestone store and ask about Fuzion zri's. They are a "W" rated tire and should offer a 40,000 mile treadwear warranty. If you stay with the stock wheel, Id go 205/55/15 or 215/50/15.

Dave

I don't know about tire wear but switching to 17's will accelerate wear in a number of suspension components. You are both right (and wrong) about the affect that a lower sidewall will have, a stiffer sidewall will aid in handling and make the ride harsher, weather that stiffer sidewall is the result of a profile change or just better tires of the same size doesn't matter. Neither of you has mentioned weight, extra weight in the wheels (even just a couple pounds) will have a negative effect on handling, acceleration and especially braking. Don't forget to check the rules where you autocross, non-stock size wheels will usually bump you up a class or two.

M758

16" wheels are probably the best for as street driven car.

Slap some 205/55 on the front and 225/50 on the back.

They will provide the right stiffness comfort charateristics.

17" wheels are too big and heavy for the 924S and will make ride worse due to the stiff sidewall. Also the car was not designed for 17" wheels so it can put extra stress on the suspension parts.

Best thing would be 16x6 and 16x7 early boxster take offs. The 7" might fit in front, but would be tight.

BTW... I race on 225/50 R15 tires with 15x7" wheels. 17" and even 16" are too big and heavy. 15" wheels are lighter and with the 225/50 tire are 1" short diameter which improves the gearing. They can work steet car, but also look a little odd with too much space in the wheel wells. Not they 225 are tough fit on the front of a 924. They can fit, but they are close both to the spring and the fender.

Verruckt

I found some 16 inch phone dials off an 87 951 in a junk yard for cheap. 16 x 7 in the front with 205/50, and 16 x 8 in the rear with 225/45 The Pole Position SO-3 tires have been great, and I have gotten as many as 15,500 miles out of a set. The ride is a not as smooth as with the stock wheel and tire package, but still better then my wifes minivan. Good luck.