924Board.org

alanbp · Joined: 07 Nov 2005 Posts: 9 Location: Aberdeen Scotland

Morning chaps

My 86 924S has what feels like warped front discs (rotors to you on the otherside of the atlantic!)

My friend had a similar problem & it turned out to be just the discs sitting badly on the hub. The discs themselve look to be in good order with virtually no wear and no blueing or cracks.

Anyone else had this is a 924/944 and is it common. The car is in for its MOT test today & I think it is something that will be picked up on.

Cheers

Alan

Lizard · Posted: Tue Nov 15, 2005 11:20 am Post subject:

you can take them off and have them turned but the way these hats/rotors go on if the wheel is torqued properly it will suck it down and into place.
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3 928s,

gohim · Joined: 02 Nov 2002 Posts: 4459 Location: Rialto, CA

The front and rear rotors only have about 1.5mm of wear thickness when new.

That means that most any wear is going to mean that they are worn past spec, and cannot be turned/ground (whatever you want to call cutting the discs/rotors).

A mistake that I have seen over and over again is over-tightening and/or not uniforming tightening of the five bolts that secure rotor discs to the wheel hubs.

The bolts are only supposed to be torqued on with 17ftlbs, but time and gain, I have seen replacement rotors attached with 50ftlbs or more and unevenly tightened to the wheel hubs. This can cause warping of the rotors.

What I suggest that you do is remove the wheel hubs (with rotors) from the car, and measure the thickness of the rotors. If they are scored, and worn (do they have athick wear ridge on the edge?), then replace the rotors. They don't cost that much. If the rotors are thick enough to take a turn, then go ahead and loosen, then properly retorque the bolts that hold the rotors to the wheel hubs, and have the rotors turned. Personally, I would probably just go ahead and replace the rotors, unless you recently changed the rotors for new ones already.

Since the brake rotors on the front of the four wheel disc brake cars are attached to the rear of the wheel hubs, proper tightening of the road wheels on the car does not affect the proper mounting of the rotors to the wheel hubs. this is not the same situation as the rear brake rotors, and the brake rotors of other cars which are held in place when the road wheel is mounted on the car, sandwiching the otherwise loose rotor between the wheel hub and the road wheel.