930 (same as 911) hubs and bearings...now what do I do?

[Craig 930 RS]

http://forums.pelicanparts.com/showt...26#post3014126

Update:

Had the bearings/races replaced up front about a month ago while in for rotor/hat replacement.
Returned from shop, MAJOR shudder up front, both sides. Never a problem before.

Return to shop. Re-do of install and drive away.........shudder virtually the same.
Installer says he tried all possibilities and (if I recall correctly what he said) that each side is .005-.010 runout. Also turns out he hasn't done this project often.

Go to shop #2. Front (and now rear) bearings and races now replaced approx 2 weeks ago.
Those same 2 week old fronts were now worn to the point where they looked ~years~ old. Shop freezes/heats to get best fit, etc.

Drive away and shudder is virtually gone, barely detectable.
Seems a non-issue, so I do a track day.

Shudder is like a cheap hotel massage.....not good.
At this point I've spent over $1,000 on the bearings/races.

What do I do now? Hubs thrashed or ?
Anyone else been down this frustrating road?

[Dutchie]

Graig are you sure the shops used the right procedure for the bearings ? most cars need them torqued down to specs. The 911/930 is diffrent from most cars in that i,m not very good at explaining how but there are lots of threads about how.
Not to hard to do yourself btw ! you also said the rotors were changed maybe look at those too while checking the bearings ?

[don911]

Yikes! sounds a little scary. If you end up tearing into it yourself, I have a bearing parcker and a bearing insert tool. I've done my bearings/races a couple of time and can help if you want.

[patkeefe]

Craig:
Does it shudder under braking, or all the time?
Did you happen to keep the old bearings and races? If so, see of there are any shiny spots in the race where the baring may be contacting it at a bad angle (not squared up).
I have seen races pressed into hubs that weren't in square, such that it will push a little sliver of aluminum in the bottom seating area of the race, and the race/bearing thus is "crooked", because it will not seat correctly. Then, every ensuing bearing change compounds the problem. The hub can be repaired, but for your application, you may need new. How much runout does the entire assembly, including the wheel have (jack the car up and spin the front wheels, you will be able to see it)?
Pat

[Nine9six]

By the method suggested above, how would you know what is rim runout (imperfections) as opposed to bearing induced runout, due to a bearing not seated correctly?

[patkeefe]

Well, it could be inferred with an indicator on the rim. The big picture I had was you can get a quick idea of what the runout is at the contact patch. I am further assuming the shudder is actually the front track becoming successively narrower then wider on each wheel revolution, which would be hub runout. When Craig mentioned .005-.010" runout, I assumed this was at the rotor surface. You could have a runout of whatever in the rotor, as long as the hub doesn't have any runout; this you would notice during braking exclusively. The source of the shudder could be caused by any number of other things, but the ancedotal information leads to the coincidence of changed bearings = wheel shudder.

Pat

[Bill Verburg]

I've seen the type of shudder you describe, under heavy braking, a # of times. Always on 930s or SC/Carreras w/ big brakes.

The issue, the struts need to be replaced.

[Chuck Moreland]

.005 to .010 runout..... where (and how) was the runout measured?

The problem did not exist before you took it in for bearing replacement?

[Craig 930 RS]

Does have a bit of a wobble in the steering at speed - stands to reason I suppose as the hub/disc and therefore the wheel & tire would be rotating at a varying lateral runout, correct?

The nearly new front races and bearings (from the first attempt) looked like hell.
2nd shop swore they looked as if never replaced, they were that thrashed apparently from
the wobbling.

I think Pat has it exactly:

"I have seen races pressed into hubs that weren't in square, such that it will push a little sliver of aluminum in the bottom seating area of the race, and the race/bearing thus is "crooked", because it will not seat correctly. Then, every ensuing bearing change compounds the problem. The hub can be repaired, but for your application, you may need new."

and in fairness, the first shop did say that constant replacing can do this.

I appreciate the help!

2nd shop also said that unless one section is heated and the other frozen - this will directly cause
the sliver of aluminum to jam in the bottom of the race seating area from what may amount to a case of an installation that could have been 'more properly performed'.

At any rate, it isn't good and it's costing a load of money for stoopid arse bearings -
I believe 1st shop said 5 thou + runout - measured off the disc face.

Basically I just want it fixed correctly and maybe the hubs 'are just old and worn out'
Never ever had a hint of a wobble until immediately after the front bearings were replaced.

[Nine9six]

Originally Posted by Chuck Moreland

.005 to .010 runout..... where (and how) was the runout measured?

The problem did not exist before you took it in for bearing replacement?

Pat,
What Chuck asks, is what I was getting to. Unless you know where your runout originates, you can make adjustments till times get better, without touching the root cause.
P.S. 930 rotor runout is spec'd at, or less than .004 TIR. I agree that you would want your hub running as close to 0 as possible.

[Craig 930 RS]

I clearly recall "the runout on your car, both sides, is 2x the factory specification" -

[patkeefe]

I usually check mine at the rotors, and at the hubs. This assumes the radial play has been taken out i.e., you could have the wheel bearings "loose", and still see little to no runout. However, if there is something boogered in the bearings, the indicator will tell.

I knew what you meant though

[Jeff Alton]

Have you tried clocking the rotors on the hubs to see if the runout reduces. For my big brake application the happy spot is less than 4 thou run out on the rotor. I achieved this by buying one replacement hub, and clocking both until the runout was 4 thou or less.

It takes time to do it, but it is a simple process.

Cheers

[DW SD]

what happened here, Craig? All this good advice with no climax? What was the wrap up?

[Craig 930 RS]

Funny you mention it - I was just giving this some thought -

Appears that the hubs have been compromised from the previous bearing attempts - despite a great shop repairing it the latest try, I still have some brake shimmy -

[DW SD]

What was the issue? Were you able to isolate how they were compromised?

Doug