1996 850R Rumbling When Braking and Half Shims

wackenhut · Post by **wackenhut** » 04 Aug 2017, 22:36

Hi,

So about a year and a half ago, I had this terrible rumbling noise when braking from the rear of the car. I learned that the issue would be resolved by installing half shims with the rear brakes. This solved the problem.

I just experienced the same rumbling now but only when braking from a higher speed and turning (either left or right). I am not sure what is going on. Could the shims or rear brake pads come out of position? It is odd that this only happens when turning and not when braking on a straight road.

Any help would be great.

Thank you.

Post by **scot850** » 04 Aug 2017, 22:55

Just to clarify the issue is with the rear brakes again?

If the noise is coming from the rear of the car and only when turning I would suggest it may not be the brakes but could be a rear wheel bearing starting to go. They like to show there displeasure when going around corners as it stresses them more than a straight line.

Only other thing it may be is the parking brake shoe(s) could have separated, but I think in this case it is unlikely as they would be noisy all the time straight or turning.

Neil

wackenhut · Post by **wackenhut** » 04 Aug 2017, 23:16

Yes, the rear brakes again!

What is strange is that the noise only happens when the brake is applied when turning a corner. The car corners fine if nothing is applied. You still think the bearings?

Post by **scot850** » 04 Aug 2017, 23:33

That is strange that it only happens with the brakes applied when turning. At any speed, even slow? If so I am less convinced on the bearings being an issue. Try checking you don't have a stuck brake pad or caliper at the rear. That could induce a rumble if the rotor is being flexed or is warped. Do you get any pulsing from the brake peddle?

Neil.

Post by **Clemens** » 05 Aug 2017, 05:12

in my case the exact same rumble/brake/steer issues was solved by a new rear caliper. i think it rubled in right turns and it was the left rear caliper which was stuck on the inside.

wackenhut · Post by **wackenhut** » 05 Aug 2017, 08:28

It is only when going fast and braking while turning, slow turns do not present an issue.

If it is a stuck brake pad, caliper...how would I tell?

Thank you.

Post by **scot850** » 05 Aug 2017, 09:17

Only way to tell is to remove the wheel and try to remove the pads. If your car has the duel pistons on the rear, leave one of the brake pads in and get someone to gently press the brake pedal and see if the piston extends. If one is ok, then open either the bleed nipple or the master cylinder lid and lever the piston back in and then repeat for the other one. If they move smoothly then the caliper is good. Check the pads have little room in the caliper on their ends so they don't jam. Check both sides.

Other issue could be the brakes are dragging. Maybe a collapsing flexi-hose. Those are a bear to do from an access perspective.

It is hard to do, but you can tape a pencil to the caliper with the pads removed and rotate the rotor and see if the tip to rotor gap varies to see if you have a warped rotor.

I should have also said, check the pads are all wearing at even rates. If on pad is thinner than the other you have a caliper issue. Naturally check the dust boots for splits or tears.

Good luck!

Neil.

PeteB · Post by **PeteB** » 05 Aug 2017, 09:32

If you look at worn rear pads it can be seen that the shims cause uneven wear
probably making them less effective as this wear happens.
Picture of uneven wear in second post of this thread:
viewtopic.php?f=1&t=81876

I'd remove the shoes as if you are doing the pads and make sure that no pads or
pistons are frozen. Lube the edges of the pads where they touch the caliper.

Maybe you can rotate the pads to even out the uneven wear on the pads, have
not thought about how to do this, side to side or? Then the shim will help again.