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Brakes Sound

Jared_

Jared_

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Jul 23, 2025
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Sorry if this is an easy/often asked question, but I couldn't find a definitive answer with a search.

My brakes are making this awful sound. Sometimes it's from the front, sometimes it's from the back, but it sounds almost like a train whistle at times. Initially I thought it was a brake pad wearing down, but since it's inconsistent, I'm not sure if it's either the brake pad dying, or there's just gunk/stuff in there. Is it something I can safely ignore/just an unavoidable occurrence (since I'm still able to brake), or is it something I should look into more seriously (since y'know, IT'S BRAKES)

Thanks!
 
Looks like you got a bike now!

Don't ignore brakes.

I remember they used to give you some goo and then there were thin sticky plates, and now I do not recall, maybe they integrate it with the pad foundation, but some kind of anti-squeal agent. It goes between the pad assembly and caliper piston as some kind of vibration absorbent.

Oh yeah, and I just remembered, it may also come in a spray can and I remember this because I went to my girlfriend's friends one thanksgiving and they were supposedly mechanics so they were changing brakes on the Amigo I rode in on and I witnessed the crankhead mechanic forget to apply the anti squeal substance and when I pointed that out, he just sprayed down the outside of the calipers. Needless to say, I immediately started the rework when I got back to the lady's house who owned the Amigo. Her name was Kate and she never said thanks. The moral of the story is though, there is no simple spray on solution to your problem, even if they sell it in a can.

A can of brake clean is good to have around too, I mean just to clean up and see what's going on.
 
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Brake cleaner! Ok, I didn't even realize that was a thing. I'll give that a try for sure. I also know that I will likely need to disassemble the brake assembly, I'm just worried about that since I've never done it before.

And yeah, I made a questionable decision and now have *two* bikes haha. It's just that the second one is Italian and picky.
 
Your brake pads have a friction material bonded to a steel backing plate. The friction material wears down with braking and the pads need to be changed before you expose the steel backing plate. First thing I would check is whether you have any friction material left. The friction material usually has some grooves cut in it with the depth of the grooves indicative of when you need to change the pads-when you can't see the grooves, it is time to change them. A backing plate coming in contact with your brake rotor will create a grinding or whining noise and destroy your rotor so should not be ignored.
 
A couple things that would definitely useful to know:

New or used bike / model year?

Mileage on the brake components?

Assuming this sound is new, when did you first notice it?

It this heard only when applying the brakes, only when off the brakes or both?

Do you notice any noise, unusual amount of drag (there will always be some drag) when pushing the bike around?
 
Squealing like a train whistle is frequently caused by the vibration / oscillation of the pad in the caliper and not worn pads. Remove the caliper from the motorcycle, remove the pads, clean the caliper piston and reassemble.

If the 'sound' you hear is more like scraping or grinding, then the pads are likely worn out.
 
It you do plan to remove and inspect the calipers this is a pretty good video on how to ensure they're installed correctly

 
Not sure if they're doing this on bikes, I haven't seen it in a while, but the last time I was looking at auto brakes, I recall that some of the thin metal backing plate, or some other flat metal piece is bent in a way such that a thin metal tab makes contact with the brake rotor at a 90 degree angle and little tab will squeal louder than a stuck nun on Christmas.

Look here I found an illustration from the Professional Motor Mechanic

1761770004470.png
 
This doesn't fit here, but here it is anyway...
That image in Post #8 reminds me of days gone by.
When I was a dealership tech I had an apprentice. He did a lot that made me wonder how long he'd last.
I gave him a simple front brake job on a full sized van. I even had someone else machine the rotors. All he had to do was a quick "pad slap".
As he beagn his road test after the "repair" we stopped him before he'd even gone 10 feet. The grinding sound from the brakes was deafening.
It turned out he's installed the pads backwards with the backing plates against the rotors and the braking material against the calipers.
That image created a vivid flashback.
That was a long time ago, but I'm pretty sure that was his last day.
 
N4teTheGreat said:
A couple things that would definitely useful to know:

New or used bike / model year?

Mileage on the brake components?

Assuming this sound is new, when did you first notice it?

It this heard only when applying the brakes, only when off the brakes or both?

Do you notice any noise, unusual amount of drag (there will always be some drag) when pushing the bike around?
Click to expand...
It's a used 2023 Aprilia RS660 that I picked up this past weekend.

Unsure of mileage on brake components specifically, but the bike had 4.9k on the odometer.

Sound wasn't there on the first day, but it was definitely there the next day.

It's only heard when applying the back brakes. I swear I hear it with the front too sometimes, but that might be unrelated.

No unusual amount of drag.


Current theory is that the brakes are dirty/glazed in some way. I inspected the brake disc and didn't see any undue amount of wear or debris. I've purchased replacement pads, but I'm hoping there's a similar solution before I attempt to replace the pads.
 
ctwo said:
Not sure if they're doing this on bikes, I haven't seen it in a while, but the last time I was looking at auto brakes, I recall that some of the thin metal backing plate, or some other flat metal piece is bent in a way such that a thin metal tab makes contact with the brake rotor at a 90 degree angle and little tab will squeal louder than a stuck nun on Christmas.

Look here I found an illustration from the Professional Motor Mechanic

View attachment 584751
Click to expand...
I'm aware of these, and it's a similar sound which is why I thought it was brake wear to begin with, but the fact that it's not 100% consistent made me think it could be something else. (Also idk if they're on bikes)
 
Given that info either pads are glazed as you noted and or the calipers were not installed and aligned with the rotors which would allow for some vibration / brake squeal. Odds are everything is OE at that mileage.

Unlikely to be the case but I've had an issue with my MTB discs where they get corroded after being stored in a concrete bike room during our rainy season. They won't not squeal and the only solution is to replace them. I'm assuming the water intrusion in that room + concrete results in something chemical happening between whatever is leached out of the concrete and the pads.
 
Ok. I'll try a brake cleaner (?) or something first when I get home, and see where that gets me. At least I have a replacement pad already available in case that's what I'll need to do.
 
Like I said, there is no spray on fix, but you do want to see what's wrong, and clean off all the components while inspecting.

Removing the calipers is not difficult, unless you have large twin front rotors. I'd want to see the brake pads, and while they are not expensive, if I see glazing, and sometimes just because, I'll just sand a bit of the surface off anyway. I'd just take it apart, clean, and install the new pads.

I use a 12mm socket to remove the <banjo> bolts, and you'll want to clean those pins and apply a very light coating of grease, and clean the capiler holes out too.

You see there could just be a buildup of brake material dust behind the pad allowing for some wiggling. Or there could be something else going on.

BTW, I also remember those brake wear indicators squealing, and they are not always consistent. In fact, now I remember on one car I could stomp the brake and make the sound go away for a while. You know, it just depends on where the pad/piston ends up sitting - it's a loose hydraulic system on the back side of that, and getting just the right pressure on that squealing tab might not always happen. It's like making a wine glass sing, it doesn't always...
 
Jared_ said:
Brake cleaner! Ok, I didn't even realize that was a thing. I'll give that a try for sure. I also know that I will likely need to disassemble the brake assembly, I'm just worried about that since I've never done it before.

And yeah, I made a questionable decision and now have *two* bikes haha. It's just that the second one is Italian and picky.
Click to expand...
Since you are novice enough to not know of brake cleaner I'm thinking someone experienced should be looking over your shoulder while any brake components are worked on. I'm 4 hours away so fergeddaboudit, must be someone closer to mentor you?

If nothing else, when you put the calipers back on the bike pump the brakes a few times until firm before riding off. Otherwise you'll have no stopping power when you go to use them at first. The pistons will have been pushed back into the castings so need to be brought back out to working position.
 
larry kahn said:
Since you are novice enough to not know of brake cleaner I'm thinking someone experienced should be looking over your shoulder while any brake components are worked on. I'm 4 hours away so fergeddaboudit, must be someone closer to mentor you?

If nothing else, when you put the calipers back on the bike pump the brakes a few times until firm before riding off. Otherwise you'll have no stopping power when you go to use them at first. The pistons will have been pushed back into the castings so need to be brought back out to working position.
Click to expand...
I have YouTube :)
 
Jared_ said:
It's a used 2023 Aprilia RS660 that I picked up this past weekend.

Unsure of mileage on brake components specifically, but the bike had 4.9k on the odometer.

Sound wasn't there on the first day, but it was definitely there the next day.

It's only heard when applying the back brakes. I swear I hear it with the front too sometimes, but that might be unrelated.

No unusual amount of drag.


Current theory is that the brakes are dirty/glazed in some way. I inspected the brake disc and didn't see any undue amount of wear or debris. I've purchased replacement pads, but I'm hoping there's a similar solution before I attempt to replace the pads.
Click to expand...
The Oem Aprilia pads glaze pretty easily in my experience. My brakes can be pretty squeal heavy as well.
 
It's a good idea to lightly sand the rotors also. Pad material is transferred to the disc, and sometimes build up will cause squealing. You do not have to open the hydraulics to change the pads. If you aren't competent to bleed your brake system DO NOT remove the banjo bolts. I would sand the discs, and replace the pads. You can remove the calipers and replace the pads while the hydraulics are connected.
 
I'd just heavily use the rear brake for a while as the pads are likely from the factory and may simply have been underused.

I rarely use my rear brakes even though I know I should use both.
 
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