Mark I

DD is a 2004 C2 - I've decided to reduce the number of bent wheels and improve the ride comfort a little by moving to 17" wheels and tires. My goal is 1) to stay as wide as possible without clearance issues; 2) non-directional, so I can rotate the rear tires side-to-side w/o unmounting tires; 3)decent tread life.

Any suggestions as to sizes and specific tires very much appreciated. Thanks!

ivangene

how many wheels have you bent?

Mark I

When I bought the car (So. Cal.) both rears were bent - one had a welded repair. Replaced those with new rear wheels + 4 tires. Both rear rims now have runout and rear tires disproportionately worn at inside (which I understand is typical b/c of the negative camber & why I'd like to be able to rotate side-to-side). Haven't run over anything memorable. Front wheels seem to have stayed true, my guess the geometry being less extreme. Since I need to replace so much anyway, I think 17s are the way to go. Thanks!

V225

Not to hijack your thread, but when wheels bend, where do they tend to bend? Is it easily visible? I'm always worried that my track wheels might be bending but they look fine...

Sneaky Pete

I'm confused. You are bending the wheels? And would 17's be better?

Mark I

Varun: Outside rim vertical is what was pointed out to me by tire tech. But, that could be a result of stress to the inside. The variation is slight enough that tire itself ran true and rebalanced OK. It seems that on a 10" rim with so much unsupported levered area is more vulnerable than the narrower front. I'm guessing in my case bumps at interstate construction, etc.. I'd be interested to know from anyone who has run both 17s & 18s what differences they have experienced.

Mark I

Pete: I suspect it is at least partly due to the smaller amount of tire between the wheel and the pavement. I may be way off on this, just seems logical. I may also be too optimistic about the difference in comfort level.

bkjwhipple

yes, with a taller sidewall you will have more cushion therefore reducing the chance of a bend... you could also switch to the "touring" shocks to allow easier travel... i run 18's, haven't bent any rims, and I run tires that I can rotate. Dunlop sp 9000's ... maybe just changing shocks and a less aggressive alignment would be worth looking at?

Mark I

Thanks BKJ. I've never needed to have the car alligned, but I think I'll have the negative camber on the rear set to the minimum specs & look into the touring shocks, depending upon the ride with the different tires.

rpm's S2

To each his own, but your solution does not seem to fit the problem. The slight advantage you might gain would not stop the sort of damage you describe, which can only come from fairly hard hits to curbs, potholes, etc.

As for rear tire wear - you bought the wrong car if you don't want to replace rears more often than fronts. That effect is more a combination of weight balance and power in the rear engined Porsche than a wheel/tire issue. Drastically changing the wheel/tire geometry from Porsche spec could have a real impact on handling and performance. Even the base 17" rim on the 996 had different wheel and tire sizes front to back.

And it sounds like you needed a good alignment by a Porsche specialist a long time ago...

V225

Thanks for the info Mark. I'll keep my eyes peeled.

ivangene

what wheels?

maybe they just need to be replaced - I would NOT go to 17" wheels on a 996 unless you are driving on winter tires for a short period of time. Its a performance car and you are reducing performance ini lue of comfort and trying to get longer tire life?

get an alignment - a real one, not some shotty one, and replace the tires when they were out.... when you get new ones TRY and were them out as fast as possible, try to keep your MPG below 15 and try and go thru a set of brakes every couple thousand miles....

In the end you will forget about the tires and have a smile stuck to your face so big you wont be worried about how long those tires didnt last and how "roough" the ride was



(or get a Honda, ask Tim how long his tires last, i bet he can rotate then to any corner he wants)

tooloud10

I'm kind of curious as to the outcome of this little project. When I was more involved with the Miata community, almost everyone shied away from bigger rims in an effort to reduce unsprung weight. The 15" BBS rims on my '95 Miata weigh less than 12 lbs. each.

I don't see anything wrong with 17" wheels at all and truly believe that the 19" and 20" models are only for the bling factor anyway. I stick with the 18" OEM models simply because everyone says that the car was designed with that size in mind, but I'd be willing to bet that going to a high-quality (read: lightweight) 17" wheel wouldn't be better for almost all aspect of the driving experience over a +1 setup.

Mark I

Ralph, Ivangene & Tooloud: Thanks very much for the thoughts. I readily accept after 20+ years of 911 driving that the rears will disappear twice as fast as the fronts - but much more evenly. I want to reduce the negative camber at the rear to the low end of the factory specs and be able to rotate the rear tires to reduce that inside corner wear. As for a resulting loss in performance, my year car (2004) was offered with both sizes (although I don't know if the cars eqipped with 17" wheels were otherwise different) and I drive so far below the car's potential, the added comfort would be nice. Thanks again, guys. P.S. Still hoping for maximum 17" tire size suggestions. Merry Christmas to all!

Macster

Well, I've run a Boxster over 237K miles on 17" wheels/tires over the entire country west of the Mississippi and have never bent a wheel. And I have encoutered some pretty gruesome potholes. One I hit it felt like the front end of the car dropped into a hole. Horrible impact and I expected a busted tire (sidewall) and a damaged wheel but thankfully neither one occurred. Alignment unaffected too.

Cast wheels require a pretty good blow to bend. If they bend they are generally considered unusable.

I have 18"s on my Turbo and have put 40K plus miles on it and have never bent a wheel. The ride's a might harsher due to the stiffer sidewalls and higher tire pressures the Turbo requires.

Also, my experience with a properly aligned car even though the rear wheels have noticable negative camber the inside tire edges do not wear faster than the outside edges. Uneven wear between the inside and outside edges is due improper rear toe settings. It doesn't take much error -- I learned the hard and expensive way -- for a set of very nice new expensive rear 18" Contis to be worn out in under 8K miles when normally I can get 12K to 15K from them.

Sincerely,

Macster.