75 911 S moving to 930 trailing arms???

[Duc Hunter]

On my 1975 911 S I’ve been having a chronic problem. The car eats rear wheel bearings at an alarming rate.

It’s a wide-body car with turbo rear flares. When I bought the car, it was set up with the turbo wide-body, and had very large spacers on the rear wheels, very much like the early 930s did. I had Braid custom build me a set of wheels, and I removed those spacers entirely, having my wheels just be much deeper dish. The wheel bolts up to the brake and hub just like it would on a narrow body car, and just like it does on my 89 3.2 Carrera.

I believe the reason I’m eating wheel-bearings is the load the wide-body flares, and the wheels that go with them, put on the standard narrow body bearings. It’s my understanding the 930 rear trailing arms have much stronger, tapered, roller bearings, to tolerate the load. One of my local Indie mechanics has suggested I get a pair of 930 trailing arms and swap them over to stop eating bearings.

What I’m curious about though is can I do this without having to change the offset of my wheels? I understand that the trailing arms are at a slightly different angle. That said, I believe the early narrow trailing arms for the turbos and the later arms both have the upgraded bearings, and similar offsets without the turbo spacers to the Carrera setup. Since my car is a 75 I assume I would have to source the early turbo trailing arms, and run them without the big turbo spacer that they typically have? Would that work? Could I use later model 930 trailing arms? Any other ideas?

Any insight into this little challenge would be appreciated. Again the biggest thing I’m trying to do is get larger bearings that will tolerate the offset that wheels that fit under a turbo flare require.

And for those that may not know it doesn’t matter whether it’s spacers or all done within the barrel of the wheel The basic problem is the leverage the outer edge of the wheel exerts on the wheel bearing inside the hub, because of the distance between the two.

[gled49]

Wheel offset will not work as the wheel flanges are further outboard. But the big challenge will be modified the torsion tube, replacing or sectioning in a Turbo torsion tube. And if u do what I did u will have to add 915 trans mounts.

[Duc Hunter]

OK, I think I understand what you’re saying.

Am I correct that the early turbo cars had very different trailing arms from the later model ones? I somehow remember that the 75 through 77 or something Turbo‘s had different wheel offsets different spacers and different trailing arms than the later 80s 930s?

And I think the real crux of what you’re telling me is that there’s no way to avoid tearing up rear wheel bearings with my current set up, being a narrow body car with widebody, fenders and wheels… Short of significant work to the rear torsion tubes to accommodate the turbo trailing arms, etc.?

[Dan J]

You might consider another approach. Over the past 25 years I've built and run
many 911 race cars with the narrow body control arms that you have with 285/35 Hoosier tires
What I learned a long time ago is that the bearings whether they be FAG or SKF do not come with sufficient grease . We pull off the seals and repack the bearings with high quality synthetic grease
and presto the bearings last a full season instead of 1 weekend
It's certainly cheaper and easier then putting in 930 arms

[gled49]

All turbos thru 89 use the same trailing arms. Only difference on early ones is brake caliper and sway bar mounting. That torsion bar pix is from 76 Turbo service info. Good luck with the project, there are easier ways.

[Jim2]

To answer your question about offset, the turbo trailing arms (all years) are 1" wider track each side, so a total of 2" wider track.

I think you may be confusing the front where 1978 through 1980.5 they use 911 hub with two piece rotor and factory 19mm wheel spacer. After 80.5 the hub incorporates the 19mm spacer dimension and uses a one piece rotor.

[Garen]

I'd give Dan's advice some thought. The man knows a thing or two about setting up 911s. He may have done a couple...

It's certainly less hassle than ripping out the torsion tube, sourcing 930 arms, etc.

[Duc Hunter]

Originally Posted by Dan J

You might consider another approach. Over the past 25 years I've built and run
many 911 race cars with the narrow body control arms that you have with 285/35 Hoosier tires
What I learned a long time ago is that the bearings whether they be FAG or SKF do not come with sufficient grease . We pull off the seals and repack the bearings with high quality synthetic grease
and presto the bearings last a full season instead of 1 weekend
It's certainly cheaper and easier then putting in 930 arms

Great idea!!! I will give that a try on the next swap.

[proffighter]

Originally Posted by gled49

Wheel offset will not work as the wheel flanges are further outboard. But the big challenge will be modified the torsion tube, replacing or sectioning in a Turbo torsion tube. And if u do what I did u will have to add 915 trans mounts.

If you are looking for a 930 turbo torsion tube, I have one cut out of an car (accident) I bought as donor for roof and rear part for my rebuilt. Can post pics if interessted. Regarding price I have no idea, but will offer for a fair one, but shipping from Switzerland will take some money.

[r lane]

I have a good friend that races an IROC style car with base aluminum trailing arms. Raced it for years hard, and never have I heard him comment on a rear wheel bearing problem. He and I regularly discuss our cars issues and that has never come up. I would be surprised to find that that stock bearing couldn't handle the load. Something else going on I would think. Bob

[Duc Hunter]

Originally Posted by r lane

I have a good friend that races an IROC style car with base aluminum trailing arms. Raced it for years hard, and never have I heard him comment on a rear wheel bearing problem. He and I regularly discuss our cars issues and that has never come up. I would be surprised to find that that stock bearing couldn't handle the load. Something else going on I would think. Bob

I don’t disagree at all. That said the car is a street car only, and ahs had the rear wheel bearings done twice in 6,000 miles. Both times I used SKF bearings too, not cheap crap. The only conclusion we can come up with is too much load from the offset. Everything is being torqued to spec, so it should not be over tightening etc.

[analogmike]

The problem with wheel bearings on '74+ 911s that have hard miles is often due to wear of the bearing hub. If the old bearing comes out easy, the banana arm is probably worn out. There are also different style nuts you can use, the ones I used early this year got loose and I replaced them with a different type. Best to mark the nut so you can see if it moves.