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rc7424 · Posted: Wed Jul 22, 2015 10:22 am Post subject: Rear Wheel Wobble on '82 931

Restoring an '82 931. Looks good from 30 feet, interior looks great, but it sat in a barn for 20 years and needs a bunch of mechanical work. I'm currently working on the rear brakes...new rotors and a caliper rebuild. I put the new rotors on and noticed that they wobble as I spin them. The old rotors were rusted on tight so I had to bang on them from the inside to get them off. Could I have bent the wheel hubs or am I looking for a different problem? Any guidance is most appreciated.
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Autonomous Vehicles are for Automonous People

'82 931
'22 Alfa Giulia
'21 BMW 840
'02 Ducati 998
'11 FXDWG
'75 Honda 750 F

jason c · Joined: 13 Jan 2014 Posts: 1018 Location: Nwi

Unlikely you bent anything unless you got super rough & used a sledgehammer or something. You most likely have rust/corrosion on the hub between the hub & rotor. Clean all surfaces well & try again.
You can check runout of the hub, a small amount off will be a lot with the wheel on.

rc7424 · Posted: Thu Jul 23, 2015 3:17 am Post subject:

I didn't beat them to death, but I had to hit them pretty hard with a mallet to crack the rust.

Removed the rotors. When I rotate the hubs I can see that there's about a quarter inch of movement on the rear left side a little less on the right.

Any thoughts?
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Autonomous Vehicles are for Automonous People

'82 931
'22 Alfa Giulia
'21 BMW 840
'02 Ducati 998
'11 FXDWG
'75 Honda 750 F

Fasteddie313 · Joined: 29 Sep 2013 Posts: 2595 Location: MI

Thaught: WOW, 1/4" runout on a hub is massive.. What are your wheel bearings up to?
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80 Turbo - Slightly Modified

rc7424 · Posted: Thu Jul 23, 2015 4:27 am Post subject:

I guess we are going to find out. Anyone know how to loosen the crown nuts while the transaxle is out? Had to pull the fuel tank.
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Autonomous Vehicles are for Automonous People

'82 931
'22 Alfa Giulia
'21 BMW 840
'02 Ducati 998
'11 FXDWG
'75 Honda 750 F

fiat22turbo · Joined: 18 Jan 2006 Posts: 4040 Location: Portland, OR

jam a strong screwdriver into the vanes of the rotors between the calipers and the caliper mounts.
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

Grenadiers · Posted: Thu Jul 23, 2015 7:08 am Post subject:

He's down to hubs, but same thing, put long strong rod of some sort, between wheel studs, and then remove nut. Might take an extension on ratchet wrench or breaker bar. I use 3/4 inch equipment for my safety~!
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'83 944 Track car.
'88 924S Track car.
'89 944 Turbo
2004 Winnebago Vectra monster RV
2012 Jeep Wrangler
2014 Kia Soul
2001 Ford F350 powerstroke

jason c · Joined: 13 Jan 2014 Posts: 1018 Location: Nwi

rc7424 · Posted: Thu Jul 23, 2015 12:05 pm Post subject:

Thanks all for the responses. I measured the hubs again as I spun them. The deviation is actually very slight, so sorry for the chicken little routine.

The rotors are cut incorrectly inside the hat and do not completely mount flush to the hub. They'll go to a local machine shop and get fixed. The mfg will reimburse me. They are Centric part number 125-37007...be careful.
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__________________________
Autonomous Vehicles are for Automonous People

'82 931
'22 Alfa Giulia
'21 BMW 840
'02 Ducati 998
'11 FXDWG
'75 Honda 750 F