Kahdmus

These wheels look in good condition and at a decent price plus are so close I could pick them up and avoid shipping!

Why wouldnt they fit my 964??? THE SELLER SAYS PRE '86 ONLY....can anyone advise?

http://cgi.ebay.com/ebaymotors/ws/eB...tem=2466374336

Cheers,

--Howard

JoeW

Howard, the link is faulty (or at least my computer won't load it). J

joey bagadonuts

I'm not sure what the specs are for the wheel, but most pre-964 911's use wheels with significantly smaller offsets than found on our cars.

Offset is the distance from the imaginary center line of the wheel to the wheel's mounting surface, where it meets the hub. If the offset is zero, the mounting surface is located exactly in the center of the wheel and rub the fender lip.



The orginal wheel offset for the 964 is 52.3mm or just a little over two inches. A common Fuchs offset is 23mm which means the mounting surface of the wheel is over an inch closer (29mm) to the wheel's center line than the stock 964 wheel. The result is that the wheel and tire will be pushed away from the car by over an inch.

23mm is too small an offset for a 964, front or rear. 50-55mm is a good range to stick to. Also, you cannot use spacers to make the early wheels fit; they will only reduce the offset even further, e.g 23mm offset plus 10mm spacer = 13mm offset. Spacers will, however, allow you to use larger offset wheels on our cars.

Often 993 wheels come with 55mm front and 70mm rear offsets. By using a 15mm spacer with the rears, the effective offset will become 55mm. Of course such a spacer adds a couple pounds of unsprung weight but if optimal performance is not your priority, then this option will allow you to use a greater number of "late" 911 wheels.

Kahdmus

Link should be fixed now!

GREAT explanation Joey, thanks! When did cup wheels first come into being? I thought later (like post 91/92) 964's were the first 911's with cups!

--H

joey bagadonuts

Note: The Negative and Positve Offset labels from the above diagram should be reversed. Technically, our cars require a negative offset wheel.

Okay, good question, Howard. What you'll often come across are replica wheels which look like they should fit our cars but were actually built to work on older p-cars. In the case of the Cup I replicas from your link, those wheels come with smaller offsets to allow early-911 owners to use the later style wheel on their car. Wheels can be a very expensive mistake if you don't check all the numbers.

The great thing about our cars is that there's an absolute glut of 17" late-911 wheels in the marketplace. Often 996, 986 and 993 owners want to upgrade to 18's. That makes for some very attractive deals on Factory wheels for us 964 owners. Real Cup II's, unfortunately are harder to come by but they come up occasionally.

I think the 17" cups first appeared on the 91 C2 Turbo, so I believe your guess is right on the money.

Kahdmus

Great info Joey, thanks for getting some clarity around it for me! Just one thing...how can you tell the offset if it isnt listed (i.e. like in the example above)?

--H

jchaley

Based on the description "these wheels will only fit 1986 and earlier 944, 928, 911 bodies" these would not fit a 964. The 86 and earlier 944 shares it's offset with 89 and earlier 911's (excluding 89 C4). The offset for Porsches with ABS (or avalible as option) is different. 964 shares offset (52-55mm) with 87+944, 90 on 911 non turbo(turbo and turbo look have larger or smaller offset depending on 993 or 996) and some boxsters and 996 (may need spacers as 18" are usually 50mmf,65mmrear for boxsters and 996 wheels)

john

Christer

the rear tyres are the wrong aspect ratio anyway...

Adrian

Not only are the offsets totally wrong but these wheels will not fit over the 964 brake callipers.
Ciao,
Adrian
964C4

Kahdmus

A whole Wheel Education for the un-eductded.....thanks guys!

--H

joey bagadonuts

To determine the offset, you must take the wheel off and measure the backspace, the distance from the rim's inside edge to the mounting surface. Next, subtract HALF of the rim's width from the backspace measurement. Convert to metric and voila!, you've got the offset.

11" wheel example

Backspace: 7"
Subtract: 5.5" (half the rim width)
Offset: 2.5" x 25.4 = 63.5mm

Tip: Lay a straight edge across the inside of the rim which you can center over the mounting surface to help you get an accurate backspace measurement.

Jeff Curtis

Kahdmus, these wheels are repros and made for earlier cars...if you supersize the righthand pic, 2nd down, you can see the integrated "spacers" if you will, that comprise the smaller negative offset that the SC, Carrera ('84-'89) and many other P-Car models used.

These will absolutely, positively and undoubtedly NOT fit a 964.

PC2

Jeff, You've got mail! (PM)

Jeff Curtis

Saw that.

Thanks for the "heads up".