Bill Gregory

We've had a number of 964's that see track time require wheel bearing replacement, both front and rear. In itself, that's not bad, just maintenance. However, we've also seen in our local region several that suffered broken rear hubs, with the failure point being around where the shaft of the hub joins the outer side of the wheel bearing. When a hub breaks there, you have the rear wheel held on by the axle nut, not a good situation. Don't know for sure whether a bad bearing causes the hub to fail or what exactly causes it.

Reason for mentioning this...I'm replacing my wheel bearings, and in inspecting my rear hubs, one of them has two slightly visible cracks started, enough that I'm replacing it. I'll probably get the other magnafluxed to ensure there's nothing starting there too, although it looks OK.

garrett376

Thanks for the head's up - I'll check mine out next time I swap my tires. Thank you Bill.

garrett376

By the way, are you (or the other cars that had failures) running 18" wheels per chance??? Or do you have spacers so the offset of the wheels is no longer factory? I am curious what the etiology would be...

Tom W

My wheel bearings (front and rear) have been failing after about 20 track days and have been a yearly replacement item. While I think that some of the problem came from using straps thought the wheels to hold my car to the trailer, I'm going to be buyiong a puller so I can learn to change the bearing myself (at the track). I run 17" wheels with 6 mm spacers in back and had been running with no spacers in front (just added a 6 mm).

Any suggestions on what puller to buy?

Bill, thanks for the post, I'll pay extra attention to the hubs when I do my next service/checkout.

Bill Gregory

You can look, but you may not see anything. At a minimum, you'd need to remove the rotor. Of the two cracks I found, the larger of the two was under the outer edge of the bearing, out of sight until the hub was pulled, and a smaller one was right at the base of the shaft.

Bill Gregory

I run 17" rims with a 6mm spacer. Two others I know of with hub failures, one runs 18" rims, and I'm don't recall about the other, and don't know if they run spacers or not.

Bill Gregory

A mechanic friend tells me the current bearings just don't hold up as well as the originals that shipped on our 964's. He's seeing about two years life on current replacement bearings. I got mine from Porsche, as they are competitively priced when sourced from a discounting dealer, and are manufactured in Japan (rears) and Germany (fronts). A friend bought SKF? bearings made in Brazil, which only held up for a year.

You need two tools, one a slap-hammer or other bearing puller to extract the hub from the bearing. The other are all the pieces to extract and install the bearings. SIR tools makes a complete kit with all sizes needed for bearing replacement, I believe it's their B90 kit. Zdmak had the best price last I looked, or you can source the individual pieces for about half the price.

Marc Shaw

Bill - could you add a photo so those of us who are less technically inclined will know what to look for (and exactly where)?

Thanks.......Marc

Bill Gregory

Here's a picture of the hub....For reference, the wheel attaches to the hub on the left and the hub shaft goes into the rear wheel bearing on the right. The white arrows bracket the crack and the black arrows point to it. The other lines on the hub are surface scratches only. What the picture doesn't show (camera couldn't get any closer) is a jagged line that interrupts the grain of the metal. Sort of like a heat crack on a rotor that hasn't opened up yet, but finer. There was another similar crack closer to the hub, above to the left just out of sight in this picture. Note, in this case, you'd only be able to see this if you were replacing your rear wheel bearings. Pulling the hub out is a destructive operation, as it usually brings half the inner bearing out with the hub.



And in case you're wondering, 964 hubs are a stocked part by Porsche, and they run around $375.

springer3

I agree stay away from SKF. They have quality problems (no affiliation, needless to say). *** (Germany, I think) and NTN (Japan) are good bearings.

Marc Shaw

Thanks for the picture, Bill.

Marc

mark lintott

Hope I'm not hijacking this thread but it is related..........

I'm interested to know what the signs of hub/bearing wear or damage might be. Reason being that my right rear wheel has a ticking noise which has recently got very noticable and is getting more and more "intense" - especially on right bends (!). I've pulled the wheel and can see nothing catching or rubbing at all and I don't have any symptoms I would normally associate with bearing failure ie grinding or roaring noise.

I'm beginning to think it must be the hub or the bearing especially as I've recently changed back from 18" to 17" wheels and last year that wheel got hit fairly heavily in a spin. Of course the OPC who did the repairs didn't pick up any problems in that area (of course)

Any thoughts anyone?

Thanks

Bill Gregory

That's normally a CV joint problem, almost a textbook description of one that's failing. If the outer CV joint is failing, you have to replace the axle as the outer CV joint is not replaceable. If the inner joint is going, you can by a replacement joint for it. Replacement axles, new, run between $300 and $400 US. Rebuilt axles are a bit less.

mark lintott

Thanks Bill. Thing is the axle on that side was replaced about 1 year ago as a complete unit/CV joints etc, as you mention. Thats what made me think it must be a bearing. Either way sounds like its not something thats going to go away so I'll have to let the OPC check it out I suppose. Feels like another big expense in the offing.

Thanks

Bill Gregory

I would inspect the CV joints for a damaged rubber boot, missing metal tie wraps around the ends, and/or grease leakage, although you would certainly hope that you wouldn't have a problem on a one year old axle.