divil

I removed my front brake pads to replace the wheel bearing (following the procedure in Van's excellent video), but afterwards when I put them back in, the wheel would not spin freely. It spins just fine with the pads out, but with the pads in it stops before turning a full revolution, almost as if the disc is warped (but it's not).

I tried compressing the pistons back further but it doesn't seem to help. I thought it might settle back to normal after some driving, but it did not. I plan to rebuild the calipers soon anyway, but is there anything I can do in the meantime to fix this?

Van

Check for debris between the hub and the mounting face of the rotor... it sounds to me like the rotor might be just a wee bit cockeyed, thus, as you spin it, it's wobbling and pushing against one of the pads.

You can also check with a dial indicator against the rotor to measure the run-out.

divil

Thanks, I'll check that. I cleaned the face of the hub while I had it off the car but it's possible there's something in there.

Van

Since you cleaned the hubs, there's another possibility... perhaps there *was* something between the hub and rotor causing a wobble, and after time the brake rotor got machined down to the point there was no run-out. But now, that the hub has been cleaned and the rotor is sitting flat, there is a new relative wobble.

divil

I'll keep that in mind. I did clean the hub when I first mounted these rotors, which was not that long ago, and I don't think they were dragging then...but I didn't really understand the impact it could have so I may not have been very thorough. I think I will get a dial indicator and measure the runout. It's the only way I can be sure.

divil

I got a dial indicator and checked...it looks like I have .020" runout on that rotor. Going by Clark's Garage that's about 5 times too high! I removed the rotor and cleaned up the hub some more, and the inside of the rotor too. Still about the same after that.

I just changed the other side today too and that's much better, at around .004", but even that is pretty much at the limit.

Is there anything I could have done to cause this, particularly to do with installing new bearings? I've never noticed any vibration or unevenness with the brakes.

Lizard944

Did you also do the races when you did the bearings? Maybe one isn't seated all the way. I'd try driving it a few miles then check it again the same way you would diagnose a loose bearing, by rocking the wheel. If it now feels loose, then the races have probably fully seated now. Tighten the clamp nut as hard as you can then back it off and set the proper tension.

divil

Yep I changed the races. I tried really hard to make sure they were seated all the way...I did quite a bit of tapping and they looked right when I installed the hub.

I have driven a few miles, and it the bearing hasn't loosened. There was some play in them on the old bearings, but they're nice and tight now.

Here is a bit more detail: I changed the bearings/races on the driver's side, then ran out of time to do the other side. The wheel was dragging but I assumed it was because I had removed and reinstalled the pads, and it would go back to normal with a little driving. The next day I drove about 6 miles to work. Everything seemed fine.

When I was going home, there was a strange, brief bearing-like noise as I was driving out of the parking garage, which seemed to be coming from the passenger side. I hadn't heard it before, but I thought that bearing might be getting worse. The noise dissapeared before I got outside the garage, so I drove the rest of the way home (6 miles). When I got home I took a closer look, and I noticed the driver's side was still dragging. Passenger side seemed ok. I didn't drive the car again.

Today I went ahead and did the passenger side bearings and races, but first, I spun the wheel, and there was zero dragging. After changing the bearings, it's much better than the driver's side, but it is dragging slightly, which it was definitely not doing before. So it does look like I've done something to cause this by changing the bearings. But I can't see how I could have seated them any more.

Van

Brake rotors are new or old?

It might be worth it to put on a new brake rotor and measure the run-out then...

divil

They're not new, I got them last year and have a few thousand miles on them. If it comes to it I'll try new rotors but I think I'll try and see if I can get the bearings seated better first. I've pretty much exhausted my own skills there so I'll probably take the hubs to a shop with a hydraulic press.

One thing I did differently on each side was that on the drivers side (the one that has the extreme runout) I just tapped the races into place with seal drivers and a hammer. On the other side, I first froze the races, and then tried using a makeshift driver made from a large bolt and some washers to squeeze the races in with the seal drivers. When I couldn't tighten them any more, I resorted to the hammer until they looked fully seated. But this may explain why I got better results on that side. I am absolutely 100% sure the passenger side was not dragging at all before I did the bearings, now it is a little.

968 GUY

New pads or old? I seem to remember when I changed a set on one of the 968's or the 951, one of the pads had worn at a slight wedge. could have been my imagination, not sure. I try to put used pads back in the same side as they came out.
Any way you can measure runout on discs only, off the hubs?

divil

Pads were replaced with the discs.

I have no way to measure just the dics, but I just pulled the disc and tried to measure runout at the hub. I wasn't able to get a perfect set up with the dial indicator I have - I had to use it an an angle to clear the studs - but there was definitely a lot of runout there on just the hub.

So I pulled the hub and put a seal driver on the race, and sure enough I could just about see a slight uneveness with the naked eye. It's hard to tell because that seal driver is pretty beaten up, but looking at the inside of the hub seemed to confirm. So I popped it in the oven for 20 minutes and then got to work with the seal driver & hammer again. That seemed to get it as close to perfect as I can tell. I know it moved a little, because some grease was squeezed out between the race and the seat on what looked like the high side.

Reinstalled, and now I have .004". Still at the limit of acceptable runout, and still a little dragging on the pads, but it's a dramatic improvement.

This time I cleaned both the hub and the mating surface of the disc very thoroughly, and so I'm sure this .004" is not coming from debirs. But maybe it could be the disc, especially considering I now have both sides exactly the same?

Van

You can also measure the rotor thickness in a bunch of places with a caliper or micrometer... This might tell you if the 0.004" is from an uneven rotor thickness or if they hub is really spinning non-concentrically.

extanker

please have a repair shop check this car

divil

I tried this...caliper showed fairly even thickness everywhere, but I realized as I was doing it that a micrometer would have been better, as there is a slight lip on the edge of the rotor. Still I think I got a good enough measurement.

Also, I noticed that the transition from the high to low points on the dial indicator was fairly smooth, so I marked the high/low points and they seem to be about 180 degrees apart, which I think points towards it being the hub or bearings. Does that make sense? Both rotors are the same in this regard. When I have time I may try re-indexing the rotor on the hub to test this.

The driver's side brakes are definitely still dragging a little more than the passenger side, but the runout measurement is about the same on both. I think I will have to take it to a shop to really get to the bottom of this. I hope I haven't warped the hubs somehow...