Rusty Rubbing Sound at Rear

zephyrus17 · Postby **zephyrus17** » Mon Jan 17, 2011 6:42 pm

When driving there is a very loud rubbing sound like a rusty bearing at the rear. Initially it was to the right in which I thought it was a wheel bearing. But now it's moved to both sides. The noise gradually grows as I speed up and resonates between 50-60kph. Then grows gradually again, but not as loud as 50-60kph. It's not RPM related, so it's not the engine. Any clue on what this is?

Garry · Postby **Garry** » Mon Jan 17, 2011 7:21 pm

Have you checked how much meat you have left on the rear brake pads. They are fitted with little tabs that rub against the brake rotor when the bads have worn beyond their serviceable limit.

de Bounce · Postby **de Bounce** » Mon Jan 17, 2011 7:25 pm

What Garry said or possibly the rear brake calipers are seized and the brake pads are dragging on the rotors.

project.r.racing · Postby **project.r.racing** » Mon Jan 17, 2011 7:40 pm

brake pads or diff.

zephyrus17 · Postby **zephyrus17** » Mon Jan 17, 2011 7:46 pm

Could it be the diff or some part in there?

zephyrus17 · Postby **zephyrus17** » Sat Jan 22, 2011 10:07 pm

Well, I put the car on the jacks and ran it with the wheels off and found that it was the brake-pads having un-even contact with the rotors. I adjusted the rear brakes really really wide and the sound was gone during the test. So I put it back to the original width, but added a bit of distance, and the noise's been down a lot.

However, I've noticed that the left rear pad doesn't go back into place when the brake pedal is released. So probably the spring needs to be replaced? I did a test drive around and there's still a tiny bit of noise, but not as bad. At least it's not a diff issue.

So should I replace the rear pads even though there's still a lot of meat left? Or Is it something to do with the rotor?

(Maybe a mod could move this to the brake forum now?)

Guran · Postby **Guran** » Sat Jan 22, 2011 10:19 pm

Don't have the springs on mine - no problem with the pads returning. Suggest you have a close look at your pad depth (as suggested already - anything less than a few mms and you should think about new pads), check the slider pins for wear & lubricate them well, and put some brake grease on the rear surface of the pads. Then adjust the grub screw to give the pads correct clearance (tighten so brakes lock, then back off about one third turn). I'm pretty sure this is all covered in a DIY guide on this forum or miata.net.

zephyrus17 · Postby **zephyrus17** » Sat Jan 22, 2011 11:58 pm

The pad is still very very thick. I've been reading my Haynes Manual and the miata.net too. Thanks for the info. I'll get some lube. What brand of grease would you recommend for the wheel bearing and other rotating areas (Not brake related)?

zephyrus17 · Postby **zephyrus17** » Mon Apr 18, 2011 3:16 pm

Dropped it down at Southern HiTech Dyno in Adelaide, (who's a great bunch) and they say the sound is from the diff! Totally didn't expect that. They said they have an open-wheel diff available that'll be $400, or I'd have to look around for a limited-slip. Since I don't do any AutoX or track days, would an open-wheel be "ok"? Advice, please!

jerrah · Postby **jerrah** » Mon Apr 18, 2011 4:33 pm

What sort of diff do you have fitted now? NA6 came with an open 4.3 stock.

zephyrus17 · Postby **zephyrus17** » Mon Apr 18, 2011 4:47 pm

I'm not too sure, actually, I guess mine is stock. I've found that MX5 Plus has a few used LSD diffs. I've emailed them and I'll be waiting for it.

$440 for an LSD at MX5+ not including shipping from brisbane to Adelaide, or $400 for a local open. Would I feel any difference for normal driving? And wouldn't the LSD be stronger?

Guran · Postby **Guran** » Mon Apr 18, 2011 6:09 pm

Which LSD? If it's a viscous I'd say skip it - most would be shagged by now and I believe they cannot be rebuilt. If it's a TorSen, then yes you would notice the benefit on twisty drives, especially the slow tight corners. But which TorSen? I or II? You'll need half-shafts too (and driveshaft?). Or some other LSD?