New 2003 996 C4S Owner--Snow Tires and Rims

I just bought a 2003 C4S. I live in Massachusetts and plan to drive this car every day of the week-right through the winter. Happy to hear from anyone that a) thinks I'm crazy or, b) knows this is doable. I need snow tires for this car and I'd like to avoid buying brand new rims if I can avoid it. At least until I have gone through one winter and can assess the results. Porsche recommends snows as follows: Front: 8 J x 18 H2 (same as front non-snow) Rear: 10 J x 18 H2 (non-snows are 11") Looks like I have no choice but to go out and try to find used rims to match these specs. Any other thoughts would be appreciated.

I am in the same boat as well--new C4S daily driver, need a winter setup. The factory turbo twist wheels in winter spec are very difficult to find, at least for a reasonable price. I'll likely go with 18" NB C4 wheels and utilize a spacer in the rear to correct the offset, so that's an option you might consider.

I think getting a new set of rims is generally the better way to go, then your not paying to have tires remounted twice a year and risking damage to the rims in the process. Also, you can get a cheaper set of winter wheels to take the salt and potholes of a New England winter on the chin instead of your summers. However, if you want to use the stock 11 inch wide rear rim the factory recommended snow tire size (265 rear) will be too stretched, but I'm told that a 275 will fit. That means the following fitment should work, and at least as of a few months ago Tirerack stocked Blizzak LM-32s in this sizing: 235/40-18 and 275/35-18 If you go with a ten inch rear, I think you could go to a 255 rear tire, or the factory recommended tire sizing, bringing some other sizing options into play. In theory, in the snow you want a narrower tire anyway (cut through the snow as opposed to float on top). I am having a set of Forgestar F-14s made with a ten inch rear for snow tires. The reason I chose them was that you can customize the offset, so you can go to a 10 inch wide rear wheel without getting a sunken appearance in the back that more conservative offsets give you. Unfortunately they need a centering ring and a different shaped bolt, but I guess you can't have it all. I'll post pics once I get my setup dialed in.

Thanks for those responses. That's helpful. Think I found some rims and tires right down the street on Craigslist that might do the trick, but my reading is that the offset will require me to use 20mm spacers in the back. Is that just a VERY bad idea? Here's the link-- https://boston.craigslist.org/bmw/wto/5846543476.html

I drove my 996 C4S in winter conditions when I owned it. I ran factory recommended sizes for wheels and tires. I bought a set of Sport Techno replicas in the correct sizes from www.wheelenhancement.com , and they worked very well. I found that a 17mm Porsche OE spacer on the rear wheels made the 10" rear wheel and 265 width tire look good. I ran a set of Blizzaks originally, and then I switched to the Pirelli SottoZero Serie II. Unless you are driving in deep snow frequently, I recommend the Pirellis.

Thanks, Dennis C. I've put in a call to wheelenhancement. They are checking inventory. They rejected the Sport Techno (I like those) rims at 10" out of hand saying you just can't get them. Seems you lucked out there. Gbug---You say you will likely go with 18" NB C4 wheels...NB meaning?

NB is NarrowBody. Factory recommendation for narrow body Mk2 (2002 and newer) is 265's winter tires on a 10" as opposed to the 285 summer width. That's what I run and it's great on my NB C2. You, having a widebody, need a spacer as per Dennis's suggestion for it to look "right" if using NB wheels or find a set of 10" wheels with a different offset. The 50 offset is for NB. 996's are great winter cars and your C4 should be even better than my C2 which has never been a problem. The ONLY real problem you may encounter is when there is either too much snow or if your snow plows make berms near driveways, intersections etc. The ride height then potentially becomes an issue and you could in theory high center it on the bottom.

I also have a 2003 C4S. An option you can consider is 235/40-18 fronts and 285/35-18 rears. These fit correctly on standard 8" and 11" wide wheels. I am told that the diameter is easily close enough for the all-wheel drive. There is no rubbing. I use Michelin A/S 3. They now have newer A/S 3 Plus which are supposedly better in snow. I find they are fine for the limited snow we get in the Pacific Northwest and better in dry or wet handling.

FWIW, my C4S came with 225/40s and 275/35s on the OEM 18" rims. No complaints...

Here's my winter setup ACE 130B Spyder Metallic silver wheels 18 x 9 ET52 and 18 x 10 ET63 with 225/40/18 and 265/35/18 Pirelli Winter 240 Snowsport RSS 18mm rear spacers with hardware (rear) Porsche C4S center caps

Fantastic, Peteb3. Why 9s in front instead of the usual 8?

Congratulations on the purchase! I bet you're all grins behind the wheel. I've been running Blizzaks snow tires for 10 years. I live in the Denver area and we don't get too much snow in the winter, but I did grow up in a mountain town that saw plenty. I have always been so impressed by how well they do in snow and ice that I just don't plan to change to a different tire. They also last a good amount of time if you switch between a summer/winter tire combination. I also have done ice racing events with the vehicle and the Blizzaks. They've really proven to be a great tire to me. I've posted a link below that gives you some good info and comparisons between different snow tires: http://www.tirerack.com/tires/tests/...y.jsp?ttid=181 Also, when it comes time to buying a new set of wheels, be sure to check out our tech article here: http://www.pelicanparts.com/techarti...el_Fitment.htm . Let me know if you have any questions!

A LOT of useful information there, PelicanParts. Thanks very much.

That's the way I found them, bought used Running them my 3rd winter now and on my second set of winter tires And we get a real winter here in Calgary, Canada Car is awesome in the winter

And then there's the story one Porsche parts guy told me that his buddy drove a 2003 C4S right through a Massachusetts winter on summers. Wasn't perfect but it worked. Bottom line seems to be you can be successful several different ways. I'm leaning towards sticking with the regular rims and using the fitment Rustler gave me above for a bunch of reasons. Those Blizzaks were available in those dimensions earlier today and now they're not--on Tire Rack. I'll track them down and will report my experiences. Thanks again to everyone who responded. Fantastic help.

Porsche parts guy did some calculations and confirmed Rustler's fitment numbers would be right and not screw up the 4 wheel drive sensors.

This is what I am running on my 2004 C4S with Dunlop Winter Sports. I found them used on RL last year with factory turbo wheels. The tires were brand new, a guy in Tacoma bought them for his turbo and didn't use them before selling the car.

I love Wintersports. Via TireRack, I got the Pirellis mentioned above. 225s and 265s on 8" and 10" rims. The rears could stand for some spacers. 2004 C4S, BBS wheels w Pirelli Winter Snowsport 225, 265.

"However, if you want to use the stock 11 inch wide rear rim the factory recommended snow tire size (265 rear) will be too stretched, but I'm told that a 275 will fit. That means the following fitment should work, and at least as of a few months ago Tirerack stocked Blizzak LM-32s in this sizing: 235/40-18 and 275/35-18" Per Rustler's suggestion above, I got the Blizzak LM-32s in these sizes for the standard rims. Both Tire Rack advisor and Porsche parts guy confirmed they should work just fine. I'd like to pick up a set of these stock rims to use for the snows. I've tried the forums here, Craigslist, Ebay. Just not finding reasonable prices (and in many cases, any listings at all) anywhere. Anyone have any other suggestions that might work?

Results are in and thanks to everyone here who helped. I bought the Blizzaks and tire sizes suggested by Rustler, plus a set of 996 Turbo hollow twist rims by putting out a request here in Rennlist. Thanks again.

Where abouts in the Hub are you? I'm over in Waltham, we should get coffee or a beer some time!

Thanks for the questions and answers in this thread since was also researching this tire size problem using OEM wheels for my 2003 C4S and now have BFGoodrich g-Force COMP-2 A/S XL 235/40-18 and 275/35-18 on the way from Tire Rack for use on my OEM C4S wheels (18 x 8 50 ET and 18 x 11 45 ET). Someone called me today from Tire Rack to make sure I ordered the correct tires! I referenced Rennlist useful info and also did the tire size calculation which shows these are going to be about 0.4" more diameter than OEM tire sizes on OEM wheels and the circumference delta between front and rear is only 0.5%. Tire Rack guy said 235/40/18 is needs 8" min wheel width and 275/35/18 needs 11" max wheel width. This link is a great tire size calculator if you want to do the math yourself and experiment with different wheel sizes and offsets and tire sizes etc... if you don't trust everything you read on the internet and want to check the math! http://www.myturbodiesel.com/1000q/t...calculator.htm I expect to use these in the snow driving to Lake Tahoe on Friday and again on Sunday if storms materialize as expected so will report back with a review if I have anything useful to share. I expect the high speed dry handling on curvy roads to be a little compromised with the slightly taller 0.2" sidewall height on each tire and more flex but the around town bumpy road and freeway comfort level should actually be better. I figure slow speed chain control area snow performance will also be just fine....or so I hope anyway.

Very happy with the selection of BFGoodrich g-Force COMP-2 A/S XL 235/40-18 and 275/35-18 for use on my OEM C4S wheels (18 x 8 50 ET and 18 x 11 45 ET). Dry road ride is actually a lot more comfortable than OEM tire size on our often bumpy California freeways, highways, and in town roads. Aggressive driving dry road handling was still very good but felt a little sidewall flex when doing 2X advised speed limit signs on mountain road curves - i.e. 60 entry on a 30 mph turn for example. Snow performance was really good after a 4 inch dump at lake level around town and roads were barely plowed. Plowed road 1 to 2 inch on curvy roads once out of town was able to comfortably and safely blow by cars with chains at 45 mph plus and felt as good as my old Audi S4 with either Pirelli or Michelin all season M+S tires. I'd recommend these tires for a C4S using OEM wheels. The fronts stick out slightly from the wheel and the rears look fine since the sidewall stretches out to the 11" wheel width. I fretted over using non standard Porsche tire sizes for a couple years and am very glad that with research here and examples of people with our C4S models and OEM wheels going ahead with this size can report good results so go for it in my opinion.

Quotes source post: 13708212

Sorry to revive an old thread, but is there any chance you could give me the contact info for the parts guy who did those calculations for you? I'm in a nearly identical situation with my NB C4 and my local dealership says they have no way to run that sort of calculation. I posted a thread asking about my situation ( Need advice on non-standard rear winter tire sizing for '02 996 C4 (NB) ), but so far I haven't gotten any responses. Thanks!

Hi, Here is the link to the excellent Tire Size calculator. Make sure to put in your wheel size, offset, new tire size, old tire size, etc... https://www.myturbodiesel.com/1000q/...calculator.htm Since 12/2016 when I last posted have had good results with the BF Goodrich for two ski seasons and have just last week bought a different size combination of Michelin Pilot Sport A/S 3 Plus after having a little sketchy drive on 50% rubber a couple weeks ago in a storm. My new size combination is 225/45/18 Front on the OEM 18 x 8 wheels (OEM is 225/40/18) with rear 285/35/18 on the OEM 18 x 11 wheels (OEM tire is 295/30/18). The car looks really good in my opinion since the Rear tires are wider and closer to OEM and the Fronts are now narrower and closer to OEM plus have an even better match between front and rear overall diameter which is what is most important for the AWD differential. However, the overall diameter is now about 26" instead of 25" so raised the car by 1/2 inch from OEM which is barely noticeable. I've yet to get on some winding roads with these tires either dry or wet/snow but after reading reviews of the A/S 3 plus am quite confident they are going to be great. Let me know if you have any other questions since have spent hours on this topic doing my research on this subject and finally am happy that I got over all the negativity about using alternate sizes on the OEM 18 x 11 rears which was not advised by many including my Porsche dealer service advisor manager among others. Steve

New Michelins 225/45/ZR18 and 285/35/ZR 18 on OEM wheels 18 x 8 and 18 x 11. Previous 235/40/ZR18 and 275/35/ZR 18 on OEM wheels 18 x 8 and 18 x 11.

Quotes source post: 15503555

Thanks 944, I've been using that calculator extensively in my research, but the recommendations in this thread are all for widebody cars like yours (as opposed to my narrowbody C4 with the 18x10 rears) and I've been having a bear of a time finding out how much difference in tire size is acceptable without exceeding tolerances for the AWD system. I just finished reading the extremely informative thread here: https://rennlist.com/forums/996-turb...cations-3.html and it seems that the only way to keep the AWD happy and useful is to have rear tires that are slightly smaller circumference (higher revs/mile) than the fronts, which is contrary to OEM-recommended winter sizes.

I think if you go with the same size tires that I just used you would be good to go. I've read elsewhere that keeping the difference between front and rear diameter to less than about 1.5% is fine for the Differential. Think about how our Rear tires wear so much faster than Fronts which must introduce a delta more than 3% by the time tires are getting thin in back. Hope this helps.

944: that's a good point about the wear rate changing these numbers! I spent all afternoon researching all of this and in the process I ended up learning some really fascinating info about the workings of the AWD system on our cars ( thread here ). Turns out the system only works properly when the rear tire is just slightly smaller than the front! If it's slightly smaller, it spins a few revs/mile faster and thus "pre-loads" the viscous coupler so that it's ready to send power forward when needed (the summer OEM size is about 1.4% revs/mile faster in the rear than the front). The head-scratching thing about that whole concept is that while the winter OEM size is better in the sense of offering a smaller contact patch, it is a slightly larger/slower tire and thus hampers the effectiveness of the AWD! Near as anyone in that thread can figure the reason for this backwards OEM recommendation is either A) there wasn't a better winter tire size on the market to recommend or B) Porsche favored the smaller contact patch as a priority over the AWD system, or both. If I was replacing the fronts it'd definitely open up more options (like your 225/45 + 285/35 combo if I could find them in stock), but since I'm trying to keep the existing fronts I think my best bet for the rears might be Michelin PA4s in 255/40/R18: they are between the summer and winter OEM sizes in diameter/circumference and just slightly smaller than the fronts to keep the AWD happy: Thanks again for your input!

Narrow body cars can use 17" Thats what I use. They work great and look good too