awilli6

Hey guys,

About a month ago I changed the right rear bearing on my 87 S4. I changed brakes and got it all put back together. The only issue I had was the bolt that runs through the top of the hub broke when putting it back together. I replaced that with bolt form NAPA.

I'm getting a rubbing noise from that wheel when braking at slow speeds. Indy said its moving when brakes are applied. Is it possible for bearing to move or is it more likely the bolt isn't holding appropriately. The bearing noise is no longer there. Indy just looked w/wheel off. Didn't really get into it. The bolt was the same size but should I have gotten it from Dealer?

Bill Ball

Wheel bearing move?? No. It's press fit super tight into the hub carrier and the axle nut should be torqued 341 ft lbs. Somebody did tighten this properly, didn't they? I've come across some that were only hand tight.

Also, a worn hub (mine got worn when I seized a wheel bearing) might move in the hub carrier/wheel bearing assembly. The brake caliper is mounted to the hub carrier, while the wheel and rotor are mounted to the hub. So, any problem like this with the hub could cause this brake issue.

The bolt at the top of the hub carrier goes through a bushing in the upper control arm. That wouldn't affect the brakes.

During the process of replacing the wheel bearing, the parking brake is disassembled. Something could have been reassembled incorrectly there.

The rotor might not be fully seated, say, from some debris bteween it and the hub or possibly warped. See if it spins true. There is a runout limit of 0.1mm for a mounted rotor. The hub also has a runout limit of 0.05mm.

awilli6

Thanks. I'll pull it all apart today

dr bob

Make sure that you put the big circlip back in when the new bearing was put into the hub. As Bill points out, the stub axle is located in the bearing by the spindle nut. The bearing is press-fitted into the carrier, but is retained by that big snap ring, in a groove in the bearing bore of the carrier. I.m thinking that there's no good way to inspect the snap ring once the hub is installed on the stub axle, since the shield is sandwiched in place there. Removing the hub will spoil the new bearing. Perhaps a starting point would be to see that the rotor is centered in the caliper frame, easy with just the wheel removed. Easy to check runout at the same time.

awilli6

Ok, I've taken everything apart and it all appears to be put together correctly. I had my Indy press out the old and press in the new bearing. I really couldn't tell you if he put the circlip back in or not. I guess the only was to tell is to press the bearing out, which will damage the bearing right?

I'll buy another bearing & clip. Is the my best option?

The rotor spins true. The caliper sit correctly on the rotor. The wheel nut is tight. By the way, no car shops here can torque to 340 ft lbs. only tractor trailer repair shops.

dr bob

If it only makes noise when the brake is applied, it isn't the bearing.

I'd go after the brakes first as the possible problem. With rear of car raised on stands and trans in neutral, you can spin the wheels by hand and listen for the noise. With a couple folks you can put the car in gear at idle and have the wheels spinning slowly as one applies brakes and the other listens. Take the wheels off and hopefully you can isolate the source.

Torquing the stub axle nut:

Divide 326 by your weight in pounds. Multiply that number by 12. Measure that many inches out on your breaker bar from the pivot pin, and put a mark there. I use blue painter's tape. Put the bar in the socket, socket on the nut so the bar is horizontal and to the right of the nut. Stand on the bar with your weight over the mark, and you'll have the correct torque.

eg: 1 Bob weight = 180 lbs. 326/180=1.81, the number of feet of leverage needed. 1.81x12=21.72, the number of inches of leverage needed. Tape mark at 22 inches from the pin. on one foot, stand with weight centered on that tape mark. No bouncing, just steady weight. If you want to be more precise, put a little loop of rope or maybe some tow/tie-down strap on the mark, looped big enough for your foot to slide in. Weight on the loop with the bar horizontal, and you've got it correctly tightened..

I looked long and hard at buying the extra-capacity torque wrench for the axle nuts. My 3/4" drive torque wrench "only" goes to 300 lbs/ft. So, after eating a few Fig Newtons, I decided that the above method would be adequate.

WallyP

I agree with dr bob - it doesn't sound like the wheel bearing is the problem.

I would jack the car and check with the wheels turning, as suggested.

awilli6

I've had it torqued to the correct specs. The problem is that the rotor moves when the brake is applied. The bearing makes no noise whatsoever since the change. If the circlip wasn't put back in, would that cause the rotor to move?

WallyP

"The problem is that the rotor moves when the brake is applied."

How? In what direction? How much?

awilli6

It moves about 1/2 inch. The rotor moves towards the caliper.

dr bob

Ditto on Wally's questions, plus:

The 4-piston fixed caliper applies the same pressure to both sides of the rotor, so a correctly operating system should not cause the rotor to move axially (towards or away from the differential in this case) when brakes are applied. A stuck piston in a caliper -might- cause this, but it would have to be really stuck.

If the circlip was left out, the bearing would be alowed to move in the carrier towards the outside of the car, away from the differential. Braking force would not immediately affect or cause that movement. You would see that the rotor is displaced in the caliper towards the outside, but there would be no specific movement on braking.

Bill Ball

You said earlier the rotor and hub spun true. Now you are saying applying the brakes moves the rotor 1/2", a huge amount. Note that with the wheel off AND IF THE TWO SMALL PHILLIPS SCREWS ARE NOT INSTALLED AND SNUG, the rotor is free to move about on the studs. Is that the case here? Regardless, once the wheel is installed and torqued, the rotor cannot move unless the hub is loose (i.e., bad bearing) AND in that case neither the rotor, hub or wheel would spin true. A small video showing the rotor spinning and the 1/2" shift would sure help me understand what you are seeing. It's not making a whole lot of sense at this point.

Mrmerlin

I would venture a guess that you have not correctly installed the lower link pin and its beveled washers between the hub and pin,
If one of these washers is missing, this will let the whole assembly pivot about 1/2 inch as the brakes are applied.
Posting pictures of the work you have done is necessary for a proper diagnosis

awilli6

I took the wheel off and had my son put it in gear. Couple of things I noticed:

1) Right rear wheel isn't spinning as freely as the left. Actually have to goose it hard to get it to spin

2) I can't get it to squeel/rub the same way it does when i'm driving down the street. While driving, its noticable 3 cars away

3) the wheel does a little backspin after brakes are applied and released

The movement information came from my Indy. I did not see it moving. If it makes a differrence, I completed a rear CV boot in that side about 2 months ago. I didn't have any problems after the CV boot was done. The only issue after the boot was the bearing.

I'm trying to attach a video but its not working. The file fails to load. My file is a .mov file and that doesn't appear to be accepted here

awilli6