Standard offset of a 7 x 15 Fuch Wheel

[ljowdy]

I have a 1973 911, currently I have Deep 6 wheels with 195/65/15 tires. I'm entertaining the thought of installing 7 x 15 Fuch wheels all around.

Does anyone know which offset will fit properly and, what tire size I can use without rubbing on a car with standard fender openings?

thanks in advance

[911s55]

The standard offset is 23.3mm, the 911R wheels are 49.
You could run width from 185 to 205 with varying aspect ratios.
I've used 205/60 BFG with 7's on my '71 Targa. With stock T-bars/Bilstein shocks they will rub in the rear under hard cornering and accelleration. When I switch back to my 185/70's on deep sixes there is no fitment issues, the tire and wheel width fit under the fender not at it's edge.
If I decide to go back to the 7's I could either install larger T-bars, raise the ride height or go to a narrower tire.
Also regarding tires, the squareness of the shoulder should be considered, BFG and Michelins are square as are other models and a more rounded sidewall to tread approach would allow better fit.

[ljowdy]

That doesn't sound right, 23.3 mm is only .91 inches. The wheel's I've seen are somewhere in the vicinity of 135mm offset or backspace. To clarify, this is the measurement taken with a straight edge across the outer diameter of the rim than from there to the surface where the wheel mounts to the rotor

[911s55]

You asked for offset not backspace, two different things.
Offset is the distance from the mounting pad/plate to the wheel center.
Backspace is the distance from mounting pad to the wheel rim, inner edge.
The backspace is 124mm or 4.9"

David

[ljowdy]

OK, so the correct wheel has it's mounting pad (where the wheel bolts to the rotor) set at 23 mm's positive from the center of the wheel with a total of 124mm backspace.

Thanks for the speedy reply and explanation.

[Bill Verburg]

This diagram shows how the terminology relates to a wheel

[ljowdy]

Thanks, I also found a similar diagram on the good old internet