911R wheels on Early Cars Revisited

[kstar]

Once again, I have found the Pelican archives to be most enriching and valuable in my quest for deeper Porsche knowledge. And once again I need to clarify some points and reduce this topic to a definitive "answer".

Mr. Anderson recommends 7x15 wheels w/ 205/60-15 tires for a 69-77 911 in his Second Edition of the "Bible".

I might assume that this 'suggestion' consciously fails to mention the 911R type wheel for reasons of cost.

I am running 205/50zr16 SO2s with 16x6 'standard' offset (x4) now on my '72. I am rubbinig on the leading edge of the front fender and caster adjustments are not going to fix this problem - too far back and these tires will rub the well.

Given a choice between 4 15x7 911R wheels and 2 15x6 deep-6 (front) and 2 15x7 911R wheels (rear), what is the best choice in a "perfect world".

1) My gut says that 4 911R 15x7 wheels with 225/50 tires is the choice. If this choice was pursued, what do you pros say about fitment? If spacers needed, what size and where: front and/or rear?

2) This choice uses 911R 15x7 in the rear with 225/50 tires and deep-6 15x6 wheels in the front - what size tires does one use in the front?! And again: if spacers, what size and where?

In a "perfect world" which option is better if you may have 300hp to the rear wheels and subsequently more weight in the back?

Note: This will not be a track application, but an aggressive street car.

I know I am asking too much from this application, but I would like to know what combination will be more effective!

Happy Holidays and thanks again to all of you folks!

Regards,

Kurt

[Randy W]

Hi Kurt, I have the second combo you mention (6x15 deep in front with 205/50 and 7x15 911R in rear with 225/50 AO32Rs). These are on my '72S with 2.7RS engine (220hp). This is a great combo and the car does not feel undertired. To make the rears fit on an early car you need longer studs (56mm) and spacers (I'm using 17mm total). This rear stud/spacer/wheel will also work with a 225/45 Hoosier with the spring plate bolt shaved down and rolled fender lips. Four 911R wheels would be even better with this tire combo, but then you would have to add studs and spacers to the front as well as buying two more R wheels. I have found that having larger tires on the rear of these cars provides a better sense of "balance" at the limits, but you may feel otherwise and want 225s all the way around. It's a great look and the increased traction will help with all that HP!

Randy Wells

[tobluforu]

Hey Randy, On my 72, not s, The widest tire i can fit seems to be a 205\50-Fender not rolled. If I increase camber in the rear i can maybe get a 215. Do you have flares in the rear? Or, is it the type of wheel that you have that makes this possible. Thanks!

[Randy W]

No flares on my '72S (blue car). It's the wheel's offset that allows for a 225 in the rear. Another option besides the pricey 911R is an "R offset" 7x15 Revolution wheel that also requires a small spacer but not longer studs.

[tobluforu]

Thanks Randy, What does the revolution wheel look like? Like a Fuch? Is there a picture somewhere of these wheels? Thanks

[Randy W]

Check out www.revolutionwheels.com
I think the RFX wheel is the one, ask for the 911R offset.

[CamB]

Please excuse the complete lack of correct technical words in this...

First up, why would Kurt have rubbing with the 16x6s running 205/50 when the SCs could fit 205/55 (which should be worse) - I thought the arches were the same?

And second, if I am comparing, say, a 15x6 to a 16x6, there is no difference in offset - correct?

Then, if I compare a 16x6 with a 16x7 (both off an SC), is the difference entirely on the "outside" of the wheel (more "dishing") or is it on the inside too?

And how do the 911R wheels fit in this equation? I know I need to go track down one of those pics with a cross section of a wheel discussing offset vs backspacing etc etc etc.

It sounds to me like the 911R wheel has more rim on the "inside" of the wheel - is this correct? If so, how much room do 911s have back there? I guess a spare inch give or take?

Thanks for helping me I have been confused on this for a while. Next question will be in regard to brakes inside these wheels .

Oh, and what is the difference between a 911 16x7 and a 944 16x7?

Thanks!

[kstar]

I'm actually running 205/55 at all four corners w/ the 16x6 Fuchs - this extra amount of sidewall probably explains the rubbing I am getting at the leading edge of the front fenders. Sorry for my error!

Re brakes, I will probably go with the 917 style brakes from the '78-'79 Turbos. These fit inside 15" wheels but I am wondering if they also work inside a 15x7 R wheel? Will the R offset provide fitment problems w/ the early Turbo brakes?

Thanks for the help so far!

Regards,

Kurt

[Reg]

Interesting thread. Thanks for this information.

I am wanting 7" rears , or maybe all around for my '70 T

I have 205 60 15 on 6" rims now that I have no problems with anywhere.

I was thinking of using 4 SC 15" diameter x 7" fronts all around my car with 205 50's on them all. My car will not be 200+ HP and I am thinking that will be plenty of grip for a 2.2 T E or S powered car.

I have 15 x 6 early Fuchs now ( I think they are deep) and wonder if two 911 R wheels will be much more money than 4 911 sc fronts.

I'd like the R wheels for rears. People say they are expensive. What are we talking here?

[kstar]

Originally posted by Reg
. . .
I'd like the R wheels for rears. People say they are expensive. What are we talking here?

I think the going rate is $1000 per wheel these days. That is what I have found in my research.

Regards,

Kurt

[Randy W]

Hey Guys ... let me see if I can help.
Cam, in answer to #2 no difference in offset, both 6x15 and 6x16 are 36mm offset wheels. In answer to #3, the offset is different for a 7x16 (23.3mm) so the difference in width is on both sides. 911R wheels have a 49mm offset (more rim on the inside), which is the largest of any Porsche wheel - that's why you need spacers to move the wheel out so 225s don't rub on the inside. There is not that much room in there! The only differences between the regular 7x16 and the 951 7x16 Fuchs is the later has countersunk lugs and more room for bigger brakes (offset is the same at 23.3mm).

Reg, regular 7x15 Fuchss with 205s should be fine for your car!

There is an excellent article in PCA's Up-Fixin Vol 10, page 90 by Allan Caldwell for helping to understand offsets, backspace, etc. Bruce Anderson's 911 Performance Handbook (pg 215) has all of the Porsche wheel offset info.

Randy Wells

[Reg]

Thanks again Randy, everyone.

I have found a pair. Now to find a second pair...and Bruce Andersons book!

[CamB]

Hmmm, so 36mm - 23.3mm is 12.7mm, or exactly 1/2". So it sorta goes 1/2" each way - makes sense. I assume 1/2" offset is matched by 1/2" more rim on the "inside"....,. wait wait wait, I am getting confused again and don't have the upfixin' article...

Off to a suitable wheel manufacturers site.... here we go, this will do...



Right. I think what I wrote above is completely wrong. Based on the picture, a 6" wheel might have 36mm offset. Moving to a 7" wheel involving a greater lip only (ie wheel is more dished), would move the centre line outwards by 1/2". Therefore... offset becomes more negative by... 1/2" as set out above. Therefore... I conclude that the 7" wheels have 1" more lip and (more importantly) the same backspacing as a 6" wheel. The change in offset is not due to different backspacing.

So... 911R wheels. I did some basic maths and basically it works out that 49mm offset implies backspacing 1" larger than the 6" wheels. Phew, so I just proved Randy right

So, you might ask where all this is going... thus, it makes sense that if you can fit bigger brakes behind a 7" wheel then you can fit them behind a 6" wheel?

However - this doesn't take into account the greater suitability of the 944 wheel, which seems to have different backspacing but the same offset.

Back to my thinking. Kurt and many others have proved you can fit 16x6" wheels under standard guards, and I have 15x6" well "under" my guards, and am pretty certain I could fit 16x6" with a 10mm to 13mm spacer under there too (and I mean under - see http://www.pelicanparts.com/cgi-bin/vb/showthread.php?s=&threadid=52380). I could MAYBE even fit a 16x7", as I could run camber and could roll the guards.

So, the question, and apologies to Kurt for jumping on his thread - does the 930 brake conversion require more than, say, a standard offset 6" or 7" 911 wheel plus a 10mm spacer? Hey - I see Kurt wants those brakes anyway, so I guess this is not OT.

Thesis over...

Cam

[Wayne 962]

I don't recommend going with 911R wheels - as they are very hard to find (in good condition), and they run about $1000 per wheel. That's an awlfully expensive option, considering that I don't think you will be able to run wider tires than a standard six on it anyways. You might get some better performance because of the reduced stresses on the tire wall, but I'm not 100% sure on that one.

You can slightly roll the fender to fit the rear 7" wheel (non-R wheel). See Project 101 in "101 Projects for your Porsche 911" for more information, and a photo as well!

-Wayne

[911driver]

I agree with Wayne. Have experimented with quite a few variations, and the "R" solution, requires tweaking of spacer sizes, 17mm spacers are not a one size fits all solution for all '72 to '77 911 cars.

Also have tried the 52.5mm (3.5mm difference from "R" Fuchs wheels") 944 phone dial wheels, again, spacer requirements were extreme.

The Revolution wheels, while having a 49mm offset, were many pounds heavier than a standard Fuchs, the last time I checked.

I recommend 205/55 x 15 on 7x15 all around on these cars with stock fenders.

With a custom alignment, and/or fender rolling, some brands of 225/50 x 15s may work.

A note of caution -- Hoosier 225/45s x 15 are actually wider than Yoko or Bridgestone 225/50 x 15 tires. Note tire tread and section width variability between brands and models when going beyond 205/55x15 tires on these early 911s.

[Wayne 962]

Hmm, didn't know non-stock was an option? Then by all means, go with a set of Kinesis. Very strong, and the lightest wheels out there. They are also custom made, and WILL fit your car perfectly. Of course, they are $750 each. My favorites are the Supercups...

-Wayne

[911driver]

Wayne,
For 7x15" wheels, original factory fuchs are readily available, depending on condition and finish, with or without caps, $150 to $250 or so, light, and strong.