luckett

What do you base this on? I don't see how you could stuff that under the wheel well.

Matt H

The fact that I have seen it done, nothing more, nothing less.
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luckett

Wtih what offsets?

Matt H

You would have to ask the owners. Search around, there are more than one set of 11s. I have pictures of a car with 13s on the front but it is a tube chassis with widebody. They are almost too small Must be nice, right?
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luckett

I can see how the 11 might fit, but I bet the 12s with stock fenders would require a bit of crow bar action!

Oddjob

11s and 12s w/ 305s on stock fendered cars? Track or street cars? I cant imagine that the tires/whls dont hit the inner or outer fender when making tight turns just getting out of the driveway. And with some body roll and loading on the track, that would be impressive to see w/o any rubbing.

Matt H

Jim, I have seen the 11s on a street car with stock (rolled fenders and coil overs). I have seen 12 and 13s on non stock fendered cars.
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Danno

"Danno, Why did you take out you RacerX951 link from your signature?"

Whoops, thanks for catching that. When I put the little guy with the sign on my sig, I didn't re-link it to my website.

"Thanks! can that be achieved using OEM wheels? There was a refernce to using rear wheels on the front."

Maybe, there's a couple of 17x9" 911 rear wheels, C2, Cups, etc. But they're all 55mm offsets, which isn't quite enough. You'll only be able to run 225/45-17 or 235/45-17 front tyres. You really want 65mm like the TurboS wheels in order to fit a 255/40-17 in front.


"Yeah big difference, you need to add +29mm to the backspacing and -29mm to the frontspacing to convert my wheels to late-offset in your comparison table.."
"Doesn't it need to be +/- 17 to correct for the difference? 17x9.5s are 52 and 17x10.5s are 35."

We don't want to introduce too many variables here. You want to keep the rim-edges on my wheels completely fixed to keep the wheel in the same location. The only variable that changes is the hub and mounting-surface location. That's 29mm between the early and late offset cars. So... add +29mm to the backspacing and -29mm to the frontspacing and you end up with your new dimensions:

EARLY: 17x10.5", 7.00/4.25" back/front-spacing = 35mm offset
LATE: 17x10.5", 8.14/3.11" back/front-spacing = 64mm offset

remove 0.5" from each edge to get a 17x9.5" wheel and you end up with

LATE: 17x9.5", 7.64/2.61" back/front-spacing = 64mm offset

With this configuration, you'll be able to run a 255/40-17 front tyre, but no more than a 225/45-17 with 52mm offset, maybe a 235/45-17 perhaps, but that's it.

FWIW, point of reference: Adrial's 17x8" 47mm offset withs with 235/45-17 tyres rubbed severely on his TurboS. This moved his wheels outward "only" about 0.7" compared to stock, but with 10mm wider tyres, it rubbed badly enough that he went with new wheels. When in doubt, move the wheels inwards with more offset.


"It is a matter of what it up front, with coilovers you could fit an 11, maybe even a 12 up there with a 305 or so. "
"What do you base this on? I don't see how you could stuff that under the wheel well."

You sure can fit a 11" up front, again increasing the offset is the secret. Here's my next set of wheels since 17" rubber in wider sizes can't be found in the proper 24.87" diameter for our cars:

FRONT: 18x11", 35mm offset , 285/30-18
REAR: 18x12", 30mm offset, 315/30-18

I might just get widebody fenders in the rear and go up to 18x13" with 335/30-18 tyres like Paul Bloomberg... hmm...

L8 APEKS

Darn you Danno!

My girlfriends always told me size didn't matter! LOL!

streckfu's

Danno,
Are there any OEM rear wheels (maybee with spacers) that would allow the use of 9" wheels up front?

luckett

That sums to an 11.25 width. Shouldn't that be 6.68/3.87 at 35mm?

Danno

"Are there any OEM rear wheels (maybee with spacers) that would allow the use of 9" wheels up front?"

Whoops, just added a comment to that, you beat me:

There's a couple of 17x9" 911 rear wheels, C2, Cups, etc. But they're all 55mm offsets, which isn't quite enough. You'll only be able to run 225/45-17 or 235/45-17 front tyres. You really want 65mm like the TurboS wheels in order to fit a 255/40-17 in front. There was one oddball 964 wheel with 70mm offset, but that's a 16" wheel.


"That sums to an 11.25 width. Shouldn't that be 6.68/3.87 at 35mm?"

A wheel's stated size, 17x10.5" is measured across the inside of the flanges on the bead-seat where the tyre sits. This is known as bead-width or inside-width. Whenever doing wheel calculations, you will measure outside-width or overall-width, which is easily done with a ruler and straight-edges with the tyres mounted. The thickness of the flanges is added to the bead-width. Depending upon how thick the rims are, the outside-width is usually 0.5-1.0" wider than the bead-width. So my 17x10.5" wheels actually measure 11.25" wide on the outside edges. Go out and measure the actual dimensions on your existing wheels. This actual measurement is what you want to use in order to figure clearances.

Usual wheel-upgrade procedure would be to measure your existing clearances and draw a picture like I did in that PDF file I posted. You'd want to remove the springs and move the suspension up and down through its travel to find the spot with the mininum clearance. Also turn the steering left & right to figure how much compression it can take with how many degrees of turning you get before the tyre hits the fender, most likely 45-degrees forwards and up on the fender.

Then with actual measurements, you can play "what if" with upgrades. So let's assume the stock 16x7" with 225mm tyre has the following clearances:

- 1.75" of space between the tire and spring and
- about 1.25" between the wheel and spring perch.
- 1.00" between outside tire edge and fender at 3" compression, zero steering
- 0.00" between outside tire edge and fender at 3" compression and 20-degrees steering

With that data, we figured we want to keep the outside edge close to where it is for maximum outside clearance and turning angle. We can also get a longer spring to move the perch lower to clear the rim completely. Along with the larger diameter rim, we can assume that the critical clearance here is only between the tyre and the spring, of which we have 1.75" to play with. We start with the stock 16x7" dimensions:

BEFORE: 16x7", 6.04/1.71" back/frontspacing = 55mm offset

Since we're going 2.5" wider and we want to keep the outside edge close to the same, we can put 1.75" of the extra width on the inside and 0.75" on the outside:

AFTER: 17x9.5", 7.79/2.46" back/frontspacing = 68mm offset

We're going to assume that due to the angle of the strut, a larger diameter wheel will place the middle of the sidewall bulge higher up and we'll end up with 0.25" clearance, down from the 1.75" we had earlier.

Serge944

CCWs (9" front, 10" rear) for early cars come in 6.75 backspacing front and rear. Thats all you need to know.

streckfu's

They make them in the correct offset for '87+ cars? Cool! Did you buy a set? How much did they run?

streckfu's

OK, why can't I find CCWs website?