Low pitched rumble from (rear?) brakes

[lonesailor]

My NA8 has just developed a loud low pitched rumble from, I think, the rear brakes when light to moderate braking, it is not every application but does happen often, seems worse when pads have warmed up a bit. I have had a look at the passengers side rear,where it seems to come from, the pads appear to have adequate material left (around 5mm against the manuals minimum spec of 1mm). I have adjusted the hand brake lever which was loose . Is it appropiate to adjust the freeplay using the allen screw on partly worn pads? or is this just used when fitting new pads ?. The sound does sound like a vibration perhaps excess freeplay?

[hks_kansei]

Usually the allen key is just for new pads, they're supposed to somewhat self adjust as they wear down.


I'd remove the pads and confirm they have plenty of meat all over, often pads will wear in a tapered fashion, so what may look like 5mm of material from the outside edge could be at zero on the inner edge.


Other than that, rear rotors may be warped, but that normally doesnt cause noise.
Or a rear wheel bearing is going/gone.

[manga_blue]

First up, the brake cable must be a fraction loose when the handbrake is off. Otherwise it cannot self-adjust. Self-adjustment only happens when there's absolutely no tension on the levers at the calipers. So if you've tightened it util there's no slack you'll have to loosen it again.

Rumbles typically come from worn wheel bearings or collapsed suspension/swaybar bushes or loose coilover mounts. Virtually all suspension noises in my NA8 transmit themselves to me from the rear passenger side, no matter where the problem really is. It's an NA8 thing. You may have to widen your search.

Test the wheel bearings by swerving left and right both uphill and downhill on smooth roads to listen for differences in sounds.

Test the bushes by jacking the car up and using a pinch bar or big screwdriver to see if arms move so much that they can touch the mounting points. Check the coilovers for looseness at the same time.

[bruce]

Diff? Low fluid level?

[lonesailor]

I decided to look a bit deeper, took of the caliper and checked the slider pins ,they were clean and smooth but the top pin was loose and one M spring was missing I have tightened the pin , adjusted the allen screw so the pads are just clear, couldn't find a m spring so assembled with just one, (it took a while and several curses to work out how to assemble the unit without losing the spring but got there in the end. took her for a test run and couldn't provoke the rumble so will call it fixed until shown otherwise, thanks for all suggestions.

[93_Clubman]

As you mention it sounded like the noise was coming from the rear passenger side brake, it's worth keeping in mind that's the caliper that usually sticks partially or fully on as corrosion begins in the caliper adjuster mechanism.