951 15" Phonies

[TZepeSH]

Hello,
I bought from a 951 the front spindles, rotors and Brembo calipers and a complete rear axle, which was disassembled.
Problem is that I have 15" Cookie Cutters that hit the calipers. I found some info on Rennlist and Pelicanparts forums, that early Phone Dials 7x15" ET23 would fit. PN is 95136210400.
I have to use 15" wheels, it is very hard here to homologate bigger wheels. I barely made it for 185/65/15 fronts and 195/65/15 rears. I have to find a set and test, hopefully they fit, otherwise I have to stay with the older sliding calipers ATE.
Did anybody test this before?

[Lanner]

There isnt a 15" phone dial wheel that will fit. The 16" phone dials will clear the calipers.

[TZepeSH]

I will not be sure until I try a set. Several people said they installed 15" phonies without problems.
My cookies are almost fitting, but there is a "strangling" in cross-section where it rubs a little. The 951 coded 15" wheels seem not to have the strangling or it is further out, and combined with et23 seems not to hit the calipers. I'll post an update when i find a set to try.
16" or larger are not an option for me, and i like so much those brakes. Maybe more than i likes my cookies.

[Piledriver]

Probably won't help, but T1s at least ALL originally came with 16" wheels... Perhaps not yours, but that was the only option until well after WW2.

Seems sort of an odd thing to restrict, but most bureaucracies are like that to some extent.

Welcome to the STF, Lanner.

TZepeSH, if that's the same Lanner I think it is, he has probably tried every possible combination of ~everything Porsche parts swap related at some point.

[TZepeSH]

I think it is him, i know him from germanlook and I think he's also behind vdubengineering. I've got some parts from vdubengineering long time ago, very good parts and support. I totally respect his advice and work.
In this matter, I still want to test, because several people here in Europe used 15" wheels with 944t bralkes. I just found a set from the same guy who sold me the brakes, and he will test on one of his cars to see if they fit. Next week I shall get the wheels if all is ok.
The legislation here states that individual homologation is needed if the wheels were not mounted by factory on the specific model. Mine is a 1303s, so different model than the older 1200. There is also the tire width, I could only homologate the original size and width, not the wider ones I have now. I've homologated 185/65/15 and 195/65/15 some time ago, and it was crazy. It's amusing they charge 500 euros to turn the steering wheel side to side to see nothong hits, and they can even reject because they want to. I don't want to go through all of that again.
What bothers me more is that 17" wheels are homologated to another 1303s, so there is data that the wheels fit, bit authorities told me that it doesn't matter, there are no two identical cars and I have to make my own homologation if I want bigger wheels. Just Romanian authorities, I would go to a TUV anytime if it were available.

[Lanner]

Welcome to the STF, Lanner.

Thank you Pile.

I think it is him, i know him from germanlook and I think he's also behind vdubengineering.

Guilty as charged!

The homologation laws seem like a headache. I've got it much easier up here in Canada, as long as the vehicle passes the provincial safety inspection there is no requirement to prove the heritage of components to vehicle.

Mock up the wheel and go from there. It's usually not the diameter that is the issue, rather the back-of-spoke-to-caliper clearance. Maybe if minor you can clearance the caliper a touch.

I did a setup last year for BoxsterS brakes (318×28, 4 piston monoblock) and made it fit under 15s. Squeeky tight!

Lanner

[Piledriver]

Std boxster rotors and the 944T are 299mm might squeak in a little easier and plenty of stopping power.
My Wilwood Superlights up front have more room than the Brembos would have, but I'm running 16s.

Careful wit the caliper sizes, a T1 (esp lowered) wants almost the same piston area front and rear.
That actually gives you something to make the rear adjustable with via a proportioning valve.

Go too big up front and you end up with a proportioning valve up front like FJCamper...

[TZepeSH]

Hopefully no clearancing on the calipers is needed. It is all in the wheels cross-section. Below is a Cookie cutter, and I marked with th red arrow where thw caliper hits. That is the "strangling" I was refering to. Cookies have that sharp change of diameter. I was missing around 5mm ET difference to not interfere (maybe something like ET15 would have worked).

s-l400.jpg

Below is a 951 15" Phone dial wheel. The profile is different, there is no sharp change of diameter, but a nice curve. Please note that the ET for both types of wheels is ET23.

s-l400 (4).jpg

We'll see, next week I can get the wheels, but maybe the guy who sells them has time to put one on a 944T that he has with Brembo brakes and see if it fits, before I buy them.

[Lanner]

Let us kniw how it works out. It looks promising on the pictures and the part number (951) suggests compatibility.

[Lanner]

Let us know how it works out. It looks promising on the pictures and the part number (951) suggests compatibility.

[Lanner]

Let us know how it works out. It looks promising on the pictures and the part number (951) suggests compatibility.

[TZepeSH]

For sure I will come back with an answer. The interesting part is that 944T (951) never had the 15" installed by factory, and they are not mentioned in the manual or option list. They were a one-year only as I understand, somewhere in 85-86, this is why there are quite rare. They might have been installed in NA 944, with the early ET. Most of the 15" Phonies are ET52, for later cars, when they were preparing for ABS (reason for the ET change). 951 had only 16" wheels installed by factory.

[TZepeSH]

New info!
The rear brakes fit without any interference. I only tested the fronts until now. Pics below, you can see quite a large distance from caliper to wheel. It is even largen in reality, the angle of the pictures makes it a bit worse.

rear1.JPG

rear2.JPG

rear3.JPG

And here is where the front ones rub:

front2.JPG

I compared the brakes and here is where the difference comes from. On the rear, the face where the wheel attaches is more to the outer of the car than the caliper, by approximately 12mm:

rear4.JPG

The front however, is more to the inside of the car, and the caliper sticks out from the face by approximately 17mm. So there is a total difference of 30mm front to rear.

front1.JPG

I can easily solve this with a 15-20mm spacer on the fronts, with longer studs. This will help me keep my Cookies, which I like a lot, and use these brakes, which I like a lot.
What problems could appear by using 20mm spacer? The ET on fronts would become close to 0. My feeling is that the ET helps keeping the center of the wheel close to the center of the bearing, to reduce wear. Having a small ET puts the wheel outer, so there will be a pulling force to the bearing. But anyway, using the ET23 Phonies would still be a problem, because the original wheels had ET52. Is my thinking right? Something like in the picture below. I marked in black what is wheel related, red what is brake related, and green resulting force vector.

ET.JPG

So is it ok to use spacers, at all, even with longer studs to make up for the sapcer thickness? This would be my preferred solution now, because I would keep both the wheels I like and the brakes.

[TZepeSH]

Today I'll buy a lot of 14mm shims to see exactly the spacer thickness needed to clear the caliper. I tested last night with 10mm and it seems right at the edge, and 20mm clears easily, but maybe I can get away with a thinner spacer. What clearance shall I shoot for?

[Piledriver]

For caliper<>wheel clearance 3mm is plenty.
Don't use a thicker spacer than absolutely required for clearance.