Moving from 18" to 17" - Any Tire Suggestions?

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!

how many wheels have you bent?

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!

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...

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

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.

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.

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?

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.

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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...

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

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)

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.

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!

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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.

I have stock 17" on my C4 - with the new Conti DW - which are very well rated in survey & tests on Tire Rack. While you would not be able to swap sides - I believe you will find these a very good deal $ wize and a very smooth ride on 17's. I doubt you will loose anything in handling in general street use. I am very pleased with these tires and have a very stiff Coil-over lowered setup.

As stated I think it would be fine, I still would like to know what wheels you have and wonder if a stronger wheel wouldnt be just as good as swapping to 17's - I had 17's on my car for winter and as much as I would say its OK... I really could not wait to get them off. Here is a pic with mine on 17's

The smaller wheel + taller sidewall makes the tires look like racing slicks.

IMO it drove a little wierd too, but those were blizzaks so not sure if that was part of it... the steerinig was extra light and girlie

What type of wheels are you considering in the 17s? I personally upgraded from the OE 17s to 18s. No major difference and no bends that I can tell. I live in NorCal and roads are decent. I try to avoid potholes, etc. when I can to avoid issues. Depends how and where you drive your car to I guess.

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That's the winter tires more than anything else, IMHO. The lightness of my steering always shocks me when I put my 18" winter wheels/tires on the car.

Put on Direzza Star Specs. The sidewalls are stiffer than aluminum.

Thanks for the replies. I have the regular 5 spoke wheels (not the twists). Staying with that general look would suit me fine, but will be scouting for interesting alternatives. I'd really like something polished, but not chrome. It's all totally subjective, but I think Ivangene's car looks fine with the 17s. Sidenote: I also picked up your link from another thread to rimsntires - the calculator is very usefull. A 265 takes you up .4" in tire height and a 275 up .7". Not sure if those increases would cause clearance issues at stock ride height or if makes sense anyway. I like Jack's idea about the Continental tire - even better, I think from the picture (if we're looking at the same tire) I think you actually can rotate them. Happy Holidays!

I'm not sure what the max. would be in terms of 17" wheels. I know the stock setup is 17x7 ET-50 w/205 50 17 up front and 17x9 ET-55 w/255 40 17 in the rear. I run this setup in the winter with hub centric spacers 5mm front and 10mm rear. There is still a significant amount of room left under the fender with this combo, especially up front. I should add that this is with the ROW M030 suspension. I think your biggest issue will be finding wheels and tires available in non-standard sizes if you try to go bigger. The ride is definitely less jarring with the 17" set but you give up a measure of control. BTW, I run 18" Sport Designs in the summer and have yet to bend a rim. Good luck with your search.

Mark I, The Conti DW is an Asymmetrical tire tread. Labeled with "OUTSIDE" on one side of the tire to keep a particular tread pattern on the out side edges of the tire for max cornering control. This said you may swap them left to right and they would be the same... However consult with TIRERACK consultants before considering this. Back in the day (yes I am that old) when radials where a new thing the story was you never want to reverse direction of the tire once it has been rolling in one direction for part of it's life. Story was that there could be belt separation caused by that reversal of rolling direction. Maybe that is not the case any more - or maybe it was an Urban Legend??? I think you would be very pleased with these tires. And if you want to go wider and taller - based on my experience the standard sizes leave a 3 MPH window in the Speedo. Strange but these replaced the OEM Conti II's in the same size but the same street-side speed radar units now show I am going 3 MPH slower - so the tire Diameter is smaller. TireRack just published another tire test with these tires against the Michelin & Goodyear competition and they came out #1. I bought them cause of the (yes it is true) frequent rain in Seattle - and they are highly rated in that aspect.

Mark I, I, too, am considering going from 18s to 17s. My '99's 18s are chrome (ugh!), dealer installed at delivery, and I see see no advantage to paying the premium for 18s and accepting the sacrifice in ride quality. Sorry tracksters. Let us know how things go. relinuca

I have a set of 17's and 18's. I like the ride of the 17's better than the 18's. When I drive on a trip I like to put on my 17's, they ride better. One time when I had the wheels off the car I weighed the tires and wheels for each size. The fronts were very close but the 18's rear tire/wheel combo was 4 or 5 pounds heaver than the 17 inch rears for each tire. Now I do not have the same tires on each but from my seat of the pants meter I feel faster on the 17's when I autocross. No way to be scientific but just a feeling. As for the looks department, I like the 18's. My 17's are chrome and well I would like something else for my 17's. For my next set of tires I am looking at the BFGoodrich G force Super Sport A S tire. I just put a set on one of my sons cars and really like them. They are directional so you would have to dismount them to change sides. I had my car realigned and my rear tires have lasted over a year now! I use to get 8 or 9 thousand out of a set of rear tires.

Thanks for the great replies and information. I just placed an order for some 17" wheels & tires from TireRack - tires are Continentals, which seem the best fit for my purposes. I�m in Germany now, expecting delivery by the time I�m back in the U.S.. First free moment I have, I�ll be making the change...(hope to clean & repaint the lug bolts in the process); then straight to the alignment shop. I�ll convey my impressions promptly. Wishing everyone happy holidays!

Wow, refreshing to know I'm not the only one with 17" wheels....and have been for 4 yrs.plus, winter and summer tires.

If you decide to get an alignment from a Porsche Technician, make sure that the gas tank is full....a little advice from my technician.

Unless you dismount the tires and reverse them on the wheel, rotating from one side to the other will not solve the inside edge tire wear. What was on the inside on the left will still be on the inside when you move it over to the right hand side. Or is one side wearing faster than the other? If the inside of the left (or right) is wearing faster than the other side, you are either driving in circles or have an alignment problem.

Interesting thread. I drove my wife's Boxster yesterday delivering some presents to relatives traveling along a smooth country winding road for almost 15 miles. It became apparent to me that the car felt much more pleasent to drive than my 996. The steering felt lighter, quicker, more responsive than what I remember feeling in the Carrera. I've noticed this before as well, and would try to re-evaluate the tire presssures and make changes to the 996 to make it better. Then it would be weeks until i'd drive the Boxster again and forget about it. The longer wheelbase of the Boxster would have the opposite effect, so I'm thinking it may have a lot to do with the 17" wheels and narrower front tires vs. the heavier, and wider on the 996. I can't say you're making the wrong decision going with the 17s.

My '99 Cab came with 18" chromies (Ugh!). So I (too) have plans to replace with stock 17"s when its time to replace the tires. Please keep us posted with your experiences. Anybody want some chrome 18"s cheap for track usage, coffee table stands, or?? relinuca

Results - carefully mounted the new wheels & tires after cleaning up the lug bolts with a wire wheel and brake parts cleaner, fine mist of "Rust Tough" silver spray paint to bolt heads, plastic sleeved socket on torque wrench. Immediate impression: the ride is infinitely more comfortable, though at first steering felt "lighter" as you guys said it would, quickly got used to it. I'm content with the appearance, but admit the 285 x 18s I had on the rear before had a more agressive look. Subjective, but for my purposes, definite A+.

And just a note... Tire pressure for the 17's is 36 Front & REAR per the Porsche notation on the 2000 C4 sticker under the hood. I would check to confirm this is the same for your MY. Tire shops insist on setting any Porsche at 36 & 44 Not good for ride or rear tire life on my other Porsche, as they do it on my 968 as well.

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Find a new tire shop--mine will happily put the pressure at whatever I tell them.