Question about centerlock hubs for braintrust

mpeastend · 08-12-2015, 09:37 AM

Any Pelicans know for sure if the 74-75 RSR, 934 & 935 centerlock hubs are the same size? By size, I mean in diameter of the hub post. I realize there are subtle differences in other measurements between them (like spacing, axle shaft size, etc.) but will a centerlock wheel bolt up the same on all three? The drive pins fit the same and the thrust cone on the nut/wheel center engages the same? I realize there are two types of nut styles as well (A & B), but they all spin on interchangeably?

mpeastend · 08-12-2015, 09:45 AM

An example of what I'm talking about. I think Byron posted this photo a while ago. It looks like a mix of various hubs from 934, 935, etc. In the photo they don't necessarily all look the same diameter but the photo can be misleading.

Cory M · 08-12-2015, 09:46 AM

post the question here:

More 935 favorite photos

a few folks with hands-on 934/935 are on that thread

tadd · 10:00 AM

If you are talking about the wheel side of the hub, then yes, they are all identical. The hub drive changed with the 962 (smaller) and the number of drive pins changed.

Of course the choices listed are different for the bearing side of the hub. The 934/5 are based on the turbo bearings/spacing. IIRC, as I have never held one in my hands, the 74 RSR is based on the earlier non turbo bearing design.

As a note, the early BBS design for the 934/5 was used on several early race cars of various makes so watch your offsets if you buy monolithic wheels.

Although a good machinist can adjust the diameter of the center hole larger giving you other wheel options, be careful with the pin drives. 6 and 12 pins have poor overlap unless the bolt circle is very different and can leave pins with too little metal supporting them although a spacer (adapter plate) can work if there is enough offset allowed.

tadd · 08-12-2015, 10:02 AM

Mine. Finally getting boxed up to go to get the nickel chrome finish redone.

The first plate shop I took them too did not treat them well and gave me the run around for 4 months.... I was pissed when I got it back rusty.

They were just going to acid dip it real quick. I told them just to give me my stuff...

mpeastend · 10:15 AM

Thank you Cory & Tadd!

Tadd, I have later-style 930 arms. Do I understand you correctly, in that I would need to use 934 (or 935 hubs) to be compatible with the larger bearings? I thought the RSR trailing arms had the same larger bearings the turbo used, due to the 14" wide wheels they were running. BTW, those centerlocks are awesome, hope they're going on a great project car!

tadd · 08-12-2015, 10:21 AM

Yes, you will need the 930 design. I'm modifying early 67 steel arms to take the larger bearings by welding in a cassette I turned on a lathe. I should update as they are actually welded in now. Its truly sad I have more PARF postings than car fix posts anymore....

Turbo arms in an SWB

I have spoken with an ex toad hall driver who is now a engine guy and the NA RSRs were small bearing design and they had as much tire as they could stuff under the fenders :-). Said they never had any issues with bearings.

mpeastend · 08-12-2015, 10:33 AM

Tadd, to be clear, you are saying that RSR centerlock hubs will not work with 930 trailing arms? Glad I asked! It's also a problem, as I see the repro RSR hubs for sale in various places but haven't seen any 934/935 hubs. I may have to contact Mr Torres from Burbank Coachworks.

tadd · 08-12-2015, 10:59 AM

The original factory non centerlock RSR cars used the narrow/small bearing spacing with lugs/nuts. I have been told that the widebody naturally aspirated 74 RSR with center locks used hubs made for the early small bearing design. I have not actually held a real 74 RSR hub in my hand so I cannot verify this. The 934 got the updated bearing design from the 930 as did the 935.

I would guess that the repops would be the big bearing as I would assume most cars that are are either big bearing 'later' model cars or early cars that have had the bananas changed.

Mr Torres is an excellent source of parts and info. He was very helpful to me several years ago.

tadd · 08-12-2015, 11:11 AM

If you compare this pic from Armandos site to this pic in the same sequence, you'll see the diff in the bearing side of the hub...even though both are listed under '74 RSR'.

Id guess the first link is a small bearing 74 while the other is a later 934/5 hub.

Parts got mixed and matched so much cause people were just doing the racing thing. Faster was the goal, not 'factory correct' :-). I would bet money, most of the original 74 cars were converted to big bearing when things were bent/broke cause the parts were there and the 'chunkier' design.

1974 Porsche 911 RSR Center-Locks - Photo 3 photo - slidevalve911rsr photos at pbase.com

2 RSR Front Center-Locking Hubs + one Rear photo - slidevalve911rsr photos at pbase.com

mpeastend · 11-05-2015, 07:39 PM

Just wanted to update this thread in case anyone else stumbles across it with the same questions. I was able to get in touch with Jim Torres who cleared it all up & was able to set me up with the proper centerlock hubs I needed. Thanks Jim (a gentleman & a pleasure to do business with)!

First off, tadds info was 100% correct: RSR, 934 & 935 hubs all the same diameter, thread, etc. They differ in offset, bearings & the style of centerlock nuts that are used.
RSR rear centerlock hubs use bearings that fit in RSR steel trailing arms, which will also fit in 911 aluminum trailing arms. I have late model 930 trailing arms and needed 934 rear hubs which are made for the larger turbo bearings (I didn't inquire about 935 hubs as I wasn't planning on using them). The front RSR & 934 hubs are the same, so no issues there.