Down but not Out!!

[Speed Dreamer]

agree: I still have them. Waiting on the Tarox front disc brakes.

Now in I'm trying to figure out what is the correct offset for my custom wheels I'm going to order. I'm going to run a staggered setup. 17x7 on the front and 17 or 18 x 9 on the back. I have a 1974 1303/super.

Front: 17 x 7s with kerscher struts. The Tarox kit with vented disc increases track by 5mm over non vented kits similar to the ones sold by Topline, cb performance, ghia disc kit, etc. What would be the correct offset to keep these wheels with 205/40 tires under stock front fenders. I'm trying to do this without using a spacer, but don't mind using a small one if necessary. The offsets offered by the wheel maker are +22/+28/+35/+37/+43/+50. Food for thought phat73vw has a 73 1303 with 17 x 7 with +40mm et/offset, that fit. I have a 74 1303 and Jon at Topline informs me that my suspension is 10mm wider per side. My thoughts after reviewing this info, and checking out searches on offset /backspacing / is to go with either the +43 or +50 offset. ???? Help me.

Rear: 17 or 18 x 9s with offsets ranging from -1 to +50. I know I will have to order 2 or 3 inch wider fenders, and will purchase whichever ones I need to get 9 inch width wheels on the back. I'll be using either Topline or CB performance rear disc brake kit.

Zen and someone else, if I recall correctly have 8.5 and 9 inch Porsche wheels on the rear. Who has the 17 x 9s, what are they using?

Zen, what rear brake kit were you using with the 2 inch spacer and 8.5 inch width wheels with I think a 55mm offset, and 3 inches wider fender. With the spacer attached doesn't that wheel have a backspacing of about +5 mm? If you visuallize the spacer as being a part of the wheel, for example if it was welded to the wheel. Am I correct in thinking that with the spacer attached to wheel, you actually decreased the offset to about +5mm.

Do the math using the Backspacing formula, or just visualize the wheels off the car, one wheel with spacer attached and one without, lying flat on the front and you are measuring the backspacing using the actual wheel. The wheel with the spacer would have the mounting surface moved by about 2 inches toward the back of the wheel. Almost giving it a zero offset going from 55mm to 5mm, decreasing the backspacing by 2 inches (50.8mm) The wheel without the spacer has backspace of 6.25 inches

??Using a 5.5 backspacing as acceptable for the rear. My thoughts when taking all this into consideration is to go with a offset of about +12mm (1/2 inch)

With a 9 inch width wheel, having a real wheel width of 10 inches, and a 5 inch center line, the +12 offset(1/2 inch), would put the backspacing at 5.5 inches; will this work? No scrubbing on the inside axles or bump stops, etc.???

Using tires in the range of 235 to 255 / 35s, do I need 2 or 3 inch fenders???

Does any of this make sense, or have I made a mountain out of a mole hill??

I have to sort of get this right the first time.

These wheels are made to order, paid in full in advance, with no refund. Please help me, all thoughts, advice, and ideas will be greatly appreciated.
Thank you all in advance.

[vujade]

right off the bat Tony, Im gonna tell you that in the front, you
will want the 50mm offset...

I ran 55mm offset on the front of my 71 with a 10mm spacer,
which is the equivilant of running a 45mm offset wheel.

So if your car is 10mm wider per side, then you would be able to
use my 55mm offset wheels with no spacer

and if you are going to increase your track width by 5mm per side
with your brakes that means you could run a 60mm offset with no spacer.

So I would suggest that you run a minimum of 50mm offset, if not 55 or 60.


Now to the rear wheels..... the 8.5" boxster wheels that Zen is running
in the rear have a 48mm offset which makes them sit out 26mm closer
to the fenders the the 7 x 17 55mm offset wheels.

Plus he is running 944 brakes and wide aluminum arms which make
the rear 3" wider per side. And he has this all under 3" wider rear fenders..

Your rear brake kit should wider your track almost an inch per side I
believe so if you wanted to run 3" wider fenders then you need to make
up another 2" with wheel offset. So that means you would have to run
a wheel with anywhere from zero offset to 5mm on a 9" wide wheel.

If you want to run 2" wide fenders, then you would need to run between
a 25mm offset and 30mm offset on a 9" wide wheel.

[Speed Dreamer]

I came to the exact same conclusion!!! I also think it would be best to run the highest offset offered for the front, which is +50mm. So that's what I'm going to order.

On the rear I picked the middle of the road with a +28mm offset. If any adjustments need to be made, the spacer will be very small. Not sure if I will use 2 or 3 inch wider fenders. Thinking about 3 inches, I'm want to tuck the tires about a 1\2 inch under the fender if a use a 18 inch wheel.

Thanks, I just really needed a second opinion to verify my calculations. I feel more comfortabe with making the purchase now.

17x7 et +50mm front
17 or 18 x 9 et +28mm rear

If anyone disagrees, please speak up. All opinions, advice, thoughts, ideas, will be greatly appreciated.