Slight Ticking Under Braking

[TostitoBandito]

Got a new sound that I'm obsessing over. This one I only noticed the other day when it was warm enough to drive around with my windows open. Under braking I hear a ticking sound from the front right which slows in frequency as you slow down before disappearing. The nature of the sound is almost exactly what you'd expect a rock in a tire to sound like, except there's no rocks in my tires and it only occurs under braking. I've been reproducing it in the street in front of my house my accelerating to about 15mph and then lightly braking. This usually gets me about 2-3 ticks from the 2-3 wheel revs after the brakes engage.

It may be coincidental because it's so hard to hear with the windows up or radio on, but I did only notice this since I put in wheel studs last week. At first I thought it was wheel spacers that I put in at the same time, but I removed those and the noise persists.

Here's what I've done:

• Inspected all four calipers and brake pads, re-lubed pads and guide pins and reassembled. Nothing out of the ordinary found, and nothing is seized or dragging.
• Verified that no wheel studs are loose. (They were all loc-tited and torqued to spec)
• Cleaned studs and lug nuts along with hubs and inner wheel surfaces multiple times, and ensured that all lugs are properly torqued.

Since the brakes seem fine and the noise only seems to occur under braking (and only from one spot), I'm really at a loss as to what it can be. My only thought at the moment is maybe a wheel bearing on its way out, but there's no play and I'd expect more/different noises while cornering and such. Does light low-speed braking usually put enough load on a wheel bearing to make it make noise when it's otherwise quiet and normal?

Any other ideas of what I should look at tomorrow?

[TostitoBandito]

I believe I've confirmed it to be a wheel bearing issue.

I went and inspected everything under there again, and there were absolutely no issues with anything rubbing or dragging to cause that noise. After driving around a bit more and listening carefully, I also hear the same sort of ticks briefly when the front right suspension is compressed abruptly (like a speed bump). Lastly, if I make a hard left turn with the steering at or near lock I get lovely groaning noises from the front right along with the occasional tick. Nothing when turning the other direction.

My theory is that the bearing has enough play where it moves a bit when the brakes are applied and causes things to be just slightly uneven between the pads and rotor and results in a tick once per rev. My caliper bushings are solid so there's no play to hide it. The groaning that I just noticed while doing test turns is a classic wheel bearing symptom from what I've read.

Off to order new bearings for both front wheels, since I may as well do the pair. They're both still original to the car as far as I know, and it has 140K+ miles and sees the track. Rears seem fine and see less stress, so I'll leave them alone for now.

[A ///Monster]

I have the opposite problem. My left rear wheel area makes a lot of clunking that increases with my speed and then disappears as soon as I touch the brake pedal. I believe I've got pad rattle from a missing or broken brake pad spring.


Back to your problem:
No wheel play? I suppose it could still be a bearing but usually when the bearing goes, it's associated with noise, brake smell and heat from the pad wearing in an unusual pattern.

Inspect the rotor for cracks and imperfections? Rock/nail/debris stuck in the tire?

[TostitoBandito]

There seems to be a small amount of wheel play, though I've never really felt a dead wheel bearing so it's hard to tell. The fact that I fully rebuilt my brakes and put in new solid bushings recently likely made what was certainly a pre-existing issue noticeable.

Yeah the first thing I did was take every caliper off to inspect the pads, rotor surfaces, and guide pins. No issues there, aside from the inner pad on my left rear that's missing it's clippy thing and clangs against the piston as the brakes are applied. Different issue. I previously had an issue with one of my front brake pads dragging due to a messed up guide pin, but that manifested as constant clicking noise while driving even when brakes weren't being applied, and was also obvious from the extra brake dust and rotor heat on the affected corner. This wheel bearing issue was different in that everything was fine until I pressed the brake pedal or turned hard, and the noise was also much more subtle and more difficult to notice.

[TostitoBandito]

Closing this out (hopefully).

Front wheel bearings replaced, and needed to be. I also now have the glorious(ly expensive) BMW front wheel bearing tool, in case anyone in the Seattle area needs to borrow it.

However, the ticking remains. Through the process of elimination due to exhaustive checks of everything else, and the fact that it's coming from both front wheels more or less equally, I believe the culprit is the rotors themselves:

PFC_V3-Rotor_WM_WM_192.jpg
These are what I have in front. I think they're just noisy as the pads slide over the many, many slots. They have less than 1000 miles on them, so it may mellow as I get a thicker transfer layer on the rotors. There's no vibration or anything, just the clickety-clacking that you can only really hear with the windows open. I imagine this speeds up to more of a drone during high speed hard braking.

Anyways, that's what I'm going with for now.

[hc1001]

Do you have SS brake lines? If so, check your brake line slack. It could be the bracket where the SS line and hardline meet.

[boarder2k7]

Do you have SS brake lines? If so, check your brake line slack. It could be the bracket where the SS line and hardline meet.

Why are the stainless lines always too short? It really isn't hard to account for the rigid segment the lazy jerks...

[TostitoBandito]

I have the TMS/stoptech lines which seem plenty long. With the wheels straight there's a big loop of slack near the hardline connection. These lines have a sliding grommet. The grommet is held by my strut, but the line can slide freely through it as necessary during cornering.

Anyways, the noise is clearly based on wheel speed (speeds up and slows down proportionally), and since the lines definitely aren't hitting the wheel/rotor/hub I don't think they're involved.

[TostitoBandito]

Reviving this. I spoke to PFC and they thought the sounds I was describing were unusual for these rotors. I heard that some two-piece rotors like these can be noisy until they warm up due to the gaps between the hub and disc, but it doesn't seem like that's the issue here.

For the life of me though, I can't find anything wrong that could be causing it.

• guide pins and bushings all freshly cleaned and lubed, and pins are snug
• caliper carriers are all very tight
• front wheel bearings were just replaced so that's not the cause
• pad and rotor surfaces all look ok
• calipers freshly rebuilt and pistons slide in and out easily
• brakes have been bled
• anti-rattle clips present
• no clearance issues, nothing is being hit by the rotor or wheel (and if it was it'd be noisy all the time not just under braking)
• wheel studs are all secure in the hub, and lugs are torqued to spec (85 ft/lb)
• wheel spacers are present in front, but not the cause (I tested without them a while back)

My best theory at the moment is that maybe my front pad surfaces are a little off-kilter from when I had some caliper dragging issues due to a bad guide pin earlier this year. Since everything is nice and clean and lubed, and these rotors are aggressively slotted, the pads might rattle under braking until everything gets evened out and baked in. I probably only have 1000-1500 or so miles on these pads and rotors, so they're all basically new.

The sound itself is coming equally from both fronts, only under braking. It's a repetitive clicking sound, not super-loud (hard to hear without windows open), at least one time per wheel revolution. Can't feel any vibrations in the pedal from it, at least not during "normal" braking on the street.

Edit:
Just did another full removal and reinstallation of calipers and pads, and bleed. Still there. I think the sound itself might be pad rattle. It's a metallic "tick" sound and it doesn't really seem to transfer any vibration to the pedal or negatively impact braking (it's just noisy). The question is what's causing it. I do have solid brass guide pin bushings, so they're probably helping to transmit any sort of vibration or noise, but I don't think they're the cause since they seem to be working fine. The only other thought I have is to scrub the rotors clean with brakleen and scrub pads and re-bed them. I've done basically everything else I can do.

[hc1001]

Perhaps your backing plate has bent towards the rotor and is making contact. Try bending it away from the rotor.

Reviving this. I spoke to PFC and they thought the sounds I was describing were unusual for these rotors. I heard that some two-piece rotors like these can be noisy until they warm up due to the gaps between the hub and disc, but it doesn't seem like that's the issue here.

For the life of me though, I can't find anything wrong that could be causing it.

• guide pins and bushings all freshly cleaned and lubed, and pins are snug
• caliper carriers are all very tight
• front wheel bearings were just replaced so that's not the cause
• pad and rotor surfaces all look ok
• calipers freshly rebuilt and pistons slide in and out easily
• brakes have been bled
• anti-rattle clips present
• no clearance issues, nothing is being hit by the rotor or wheel (and if it was it'd be noisy all the time not just under braking)
• wheel studs are all secure in the hub, and lugs are torqued to spec (85 ft/lb)
• wheel spacers are present in front, but not the cause (I tested without them a while back)

My best theory at the moment is that maybe my front pad surfaces are a little off-kilter from when I had some caliper dragging issues due to a bad guide pin earlier this year. Since everything is nice and clean and lubed, and these rotors are aggressively slotted, the pads might rattle under braking until everything gets evened out and baked in. I probably only have 1000-1500 or so miles on these pads and rotors, so they're all basically new.

The sound itself is coming equally from both fronts, only under braking. It's a repetitive clicking sound, not super-loud (hard to hear without windows open), at least one time per wheel revolution. Can't feel any vibrations in the pedal from it, at least not during "normal" braking on the street.

Edit:
Just did another full removal and reinstallation of calipers and pads, and bleed. Still there. I think the sound itself might be pad rattle. It's a metallic "tick" sound and it doesn't really seem to transfer any vibration to the pedal or negatively impact braking (it's just noisy). The question is what's causing it. I do have solid brass guide pin bushings, so they're probably helping to transmit any sort of vibration or noise, but I don't think they're the cause since they seem to be working fine. The only other thought I have is to scrub the rotors clean with brakleen and scrub pads and re-bed them. I've done basically everything else I can do.

[TostitoBandito]

Dust shields are largely gone, and the portion that remain are well clear.

My current thought is that the outer pad is just jostling around, probably because I've removed and reinstalled them so many times recently with fresh grease. I think the ticking might be the anti-rattle clip as the pad moves. I'm gonna bend the clips for higher tension, and also clean all the grease off the back of the outer pads and put some sticky brake quiet stuff on there to try and hold them still. We'll see what that does.

[TostitoBandito]

Ok, that theory was wrong. I just put the outer pads back in with some brake quiet and put higher tension on the anti-rattle clips to no avail. Here's a clip of the noise. You can hear it towards the end while I'm braking.



Any other ideas?

Again, these are PFC 2 piece rotors with stock calipers (freshly rebuilt), ECS bronze guide pin bushings and new guide pins (freshly lubed), PFC Z rated pads, and new Stoptech steel lines. Brake Fluid is Castrol SRF and is freshly bled. Brake function seems fine and there's no vibration. Just this noise, and only while braking as far as I can tell.

[Chuck Baader]

All my race cars did just what you described since I removed the springs from the calipers...they don't look like a race car

[TostitoBandito]

To close this one all out, this went away after a track day of getting the front rotors good and hot for the first time. My guess is that it was either imperfections around the slots that got ground flush, or some play in the retaining spring clip that attaches the ring to the hub which disappeared after heat cycling.