I have the sport design 18"
The front offset / ET are 50mm
Rears are 65mm

No spacers required, perfect fit.

 

Offset num bers should be posted with a positive and negative direction I guess, but they aren't. Most 996 factory front wheels seem to have 55 of negative offset. That means the center of the tire is 55mm inside the mounting face of the wheel, where it bolts to the rotor and hat. "More offset", in this case, means that the tire centerline should be in the 65mm range inside the mounting face.

The original front wheels on most 928's are 7" wide with a 225 width tire. Some folks want to put wider wheels on the front, with wider tires. If you find a set of 7" wide front wheels that has the 55mm negative offset typical to 996 fronts, you give up half an inch of tire clearance to the outside edge of the fender. If you decide to buy 8" wide wheels with 55mm negative offset and a 245 width tire to go with it, you are giving up about an inch of clearance between the tire and the fender lip. Do you have an inch there to spare?

The issue of "tramlining" is caused by the tire moving outward from the suspension centerline. Any disturbance in the rolling resistance of the tire will have a greater effect on steering. The 928 features a "negative scrub radius", a fancy phrase that says that the center of the tire's contact area with the ground is inboard of the suspension, so that any disturbance in the rolling resistance on a front tire will cause it to want to turn towards the center of the car rather than away from it. Because that resistance to rolling is actually on one side of the car, the effect of the resistance on the total attitude of the car is neutral. Now move the wheels out slightly (not enough negative offset), and those irregularities in the road, grooves, ruts, potholes, etc., will all work to try to turn the car. You end up fighting th ecar to keep it straight on uneven surfaces. It can be particularly troublesome when braking on uneven surfaces too.

Some folks claim that theyt have success using front wheels with less than 55mm of negative offset. I've tried a couple combinations and can report that there's a very noticeable difference. My recommendation, therefore, would be to avoid anything less than 55, and look instead for something with more if you can find them. The 997 front wheel offsets are very close to the ideal for the 928. As you go wheel shopping, look for 997 Carrerra III takeoffs. They are commonly available in 18" sizes, and look quite nice on most 928's.

Hope this helps!

 

We did the exchange on the old 79 at thunderhill. the C2s fit well, but the 996 wheels, with their 9" front wheel is going to stick out about an " on the fender. wasnt even close. (2000 996)

with an 8" rim up front, that offset might work, but with a 9, the back spacing is such that the wheel just wont fit.

Here are the C2s with 205s, here are the 9.5" forgelines with 8" backspacing
and last, the Holbert car with the kinesis and 8" backspacing. (like 70 ET)

mk

 

I don't see a wheel width for these wheels posted. With most 996 fronts being 8" and these having 225 wide tires, I'd say these are probably 8+/-.5.

 

So do I buy them or not !

Me suffering with confused.com.......

http://cgi.ebay.co.uk/ws/eBayISAPI.d...:X:RTQ:GB:1123

 

Hi Nadine

NO....you shouldn't...for several reasons...

1...No ET number ( ET or offset on genuine Porsche wheels is ALWAYS stamped next to valve...so they ARE NOT GENUINE! )

2. Too expensive for copies that may or MAY NOT FIT....!!

3. NO pictures of tyre tread so forget 4 to 5 mm....they are probably bald...lol

I would leave them if I were you

All the best Brett

 

.....only if you okay with the distinct possiblilty that these wheels might NOT fit your car. But you can always resell them on Ebay.

You got a lot of good information on offsets in this thread but the bottom line is, you don't know what your getting with these wheels until you try them on your car.

IMHO I would pass on these and do a little more research.

 

02-03 996 10 spoke, 17x7 50mm front, 17x9 55mm rear no problems

 

thats because its a 7" rim. I was under the impression that the 996 was 9s and 10s. at least, thats what we had on that 996. might have been a different wheel combo entirely. BBS's.

Mk

 

Nadine, those are very nice looking wheels - particularly if they are Gemballa.
I'd be very hesitant to pull the trigger on a set of wheels (particularly in the £ 799.00+ range) without knowing for sure what the offsets are. If the fronts are anything under 50mm, going from stock 928 wheels to these wouldn't be a handling upgrade; they'd be a handling downgrade. They'd look mighty nice, but for that kind of money, you want the right fit.
I'd also ask the seller how they know that these are Gemballa wheels.
Take your time and get the right offsets. For the amount of money that you're considering spending on a set of used wheels, it's worth the wait to get something that fits.
EDIT: Assuming that you're in UK, I don't know if the style of 18" Cayman S wheels are available there. These are a great fit for our cars, in that they've got a 57mm front offset. You may get lucky and find a new-car takeoff set of these there, like you can here. Here's what they look like on a 928. They may not be your cup of tea, but I like them.