thorin

Hi guys, need some help on wheel sizes. I just called a local tire shop that I've been using for years (on my bmw) and asked them what winter wheels and tires I could use for my C4S. It happened that they had a set of 18" twist rims w/ porsche center caps lying around from another customer didn't want em back and sold em to these guys. I am able to get a pretty decent deal on a whole package.

My question is - do I have to worry whether these rims will fit my c4s? what if they're from a c2? are there offsets and stuff i have to worry about when it comes to winter wheels? or do all 996's have wheels that are interchangeable.

Ray S

Narrow body cars utilize a different rear wheel offset than wide body cars.

Post up the offsets and someone here will let you know if they will work.

thorin

Yeah, but will it damage the car even if the offsets are off? or is it just a matter of not fitting?

Ray S

Yes incorrect offsets can damage the car. They can rub the fenders at one extreme and sever brake lines or rub suspension components at the other extreme.

Just post the offsets of the wheels you are looking at (if you don't know call up the seller and find out, it should be stamped on the wheels) and we can tell you if they will fit.

thorin

so i just called back the tire shop... he said it would be a test fitting and if they don't fit, then we'd order up another set. he said the offsets were 50mm all around... does that make sense... i know my fronts are 50mm and my rears at 45mm...

ArneeA

For the turbo twists, there are two numbers by the valve stem. One is the width of the wheel and the other is the offset.

For my C4S, the front is something like this: 8 (valvestem) 50

The rear is: 11 (valvestem) 45

gota911

50mm offsets front and back does not make any sense to me unless all 4 wheels are 8" wide, which you don't want.

The narrow body offsets will work on your car but the outer edge of the wheel will retract 20mm compared to your current wheel. That is a little more than 3/4" the wheels will recede into the fender well. If you added 17mm spacers they would be about the same as your current wheels. That may be more trouble than it is worth.

Your best bet is to get the correct offsets from the start so you don't have to try to "make them fit."

Ray S

Ok,

Here's the deal. I believe the stock wheel size and offsets for the C4S are;

Front: 8 x 18 et (offset) 50mm
Rear: 11 x 18 et 45mm

As long as the wheel widths are ok (you didn't list widths) they should fit fine (however they will not fill out your fenders quite as well). A 5mm difference in offset will not be a big deal. Once you get the wheel widths you can check the difference (vs stock wheels) with the calculator in the link below (or post them here and we can help) .

http://www.1010tires.com/WheelOffsetCalculator.asp

Next step tires.......what size rubber where you planning on using?

Ray S

Tim is right, using the stock size, width, and offset is the easiest course of action. However, there is nothing wrong with playing with the size and/or offsets (within reason) to achieve a desired result.

For example for snow tires, you may not want to use the full 11" wheels so you can select a narrower tire that will work better in the snow. For summer tires you may want something that fills out the wheel well a little better and switch to 12's)

The key (IMHO) is to select the tires and wheels together so you can optimize them for your desired use (looks, track performance, winter performance, etc.).

ElTorrente

You may want to check out Tirerack.com.

They have winter wheel/tire packages for your specific car, and have great prices. They'll even do a "Hunter Roadforce balancing" at no extra charge.

thorin

That is part of the problem - the guy doesn't know what the widths are either off the top of his head and he doesn't have the time today (saturday tends to be their busiest day here in Toronto) to go find em and figure it out... I suspect that most likely these are rims from a 996/C2. Although potentially they could be from an even older 911 as well. Basically I just don't have enough info.

The tires he's recommending are 235/40/18 and 265/35/18 for the rear. The good thing is that I can go there tomorrow and check out the wheels to see if they'll work for me. If not, I can always ask for a new set of wheels.

Also the tires are Kumho - are these any good? I want to do this as he quoting $2000 for the full wheel and tire package which is very cheap here in Canada - usually these things run about $3000 atleast if you use original rims.

Ray S

This "guy" sounds like a real "tool". Who sells wheels without having this basic information???

The size he is recommending sound good for winter use, but if the rear size is stock (11") 265's are really too narrow for them.

Finally, you said you wanted "winter wheels". To the best of my knowledge Kumho does not make winter tires (only all-season).

It sounds like you are looking at dropping some real coin on this for your car. I'd suggest you talk to someone who is willing to spend the proper amount of time with you.

Try these guys;

www.tirerack.com

www.wheelenhancement.com

thorin

To be fair to him, he is not a wheel guy. All he does is tire changes. He just happens to have a set of wheels from another porsche which he is willing to offer for a cheaper price. But you are right. 2k is not a joke as far as pricing is concerned. If they're not the correct wheels, then I'll keep looking.

what is the correct width for 265 tires? 10s?

ElTorrente

Get Blizzaks or Michelin Alipines if you are going for *real* winter tires. These are the best options for high performance cars, and they supposedly perform as advertised. Everyone I've seen who owns them loves them and swears by them.

Check out Tirerack.com and get the best tires and the proper wheels, you won't regret it. They are cheap, too.

Ray S

According to Tire Rack the optimal size is 9.5". However the size range (that will work) is 9" to 10.5".

So, 10" wheels would work just fine.