# Another bike post (brake question) **URL:** \ **Category:** In My Humble Opinion\ **Created:** [June 8, 2025, 6:25pm UTC](https://boards.straightdope.com/t/another-bike-post-brake-question/1019340 "2025-06-08T18:25:21Z")\ **Posts on this page:** 19\ **Page:** 1
**Author:** ![RivkahChaya](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rivkahchaya/32/8919_2.png) [@RivkahChaya](https://boards.straightdope.com/u/RivkahChaya)\ **Post date:** [June 8, 2025, 6:25pm UTC](https://boards.straightdope.com/t/another-bike-post-brake-question/1019340/1 "2025-06-08T18:25:21Z")
So, rear brakes are squealing. They do it only when applied almost fully. If I just tap the brake to slow a little, it doesn’t make a noise; they do it only when applied fully, or almost fully, whether I get there slowly, or slam them on quickly. I confirmed under safe testing conditions that the front brakes are fine. These are disk brakes. If they were the old grip brakes that bikes used to have with the clamps that gripped the rim of the wheel, I could fix the problem myself. I put this in IMHO instead of Factual Answers, so people can feel free to recount stories of brake issues that may of may not apply, and I may have a Jeff Goldblum moment, and realize what I need to do, while hearing about someone else’s unrelated problem. Also, so people are free to recount tangential stories, and the thread can drift once my brakes are fixed. Oh-- and this is on the new ebike, so it isn’t wear. ---
**Author:** ![Reply](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/reply/32/15952_2.png) [@Reply](https://boards.straightdope.com/u/Reply)\ **Post date:** [June 8, 2025, 6:30pm UTC](https://boards.straightdope.com/t/another-bike-post-brake-question/1019340/2 "2025-06-08T18:30:56Z")
This happens to all the disc brake bikes I’ve had. Tends to get better over time. You can try this: [How to bed in new disc brake pads | 4 easy steps for fuss-free braking | BikeRadar](https://www.bikeradar.com/advice/workshop/how-to-bed-in-new-disc-brake-pads) Or else bring it back to the shop and they can lightly sand the brake disc for you (or something like that, that’s how they explained it to me) ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [June 8, 2025, 6:34pm UTC](https://boards.straightdope.com/t/another-bike-post-brake-question/1019340/3 "2025-06-08T18:34:10Z")
It might be: - Glazed Brake Pads: When pads overheat or are used improperly during break-in, they develop a hard, shiny surface that reduces friction and causes noise. - Improper Bed-In Process: New pads and rotors need proper bedding. (those kinda go together in my mind) ---
**Author:** ![RivkahChaya](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rivkahchaya/32/8919_2.png) [@RivkahChaya](https://boards.straightdope.com/u/RivkahChaya)\ **Post date:** [June 8, 2025, 8:21pm UTC](https://boards.straightdope.com/t/another-bike-post-brake-question/1019340/4 "2025-06-08T20:21:06Z")
So what exactly did I do wrong? my acoustic bike also as disc brakes, and they don’t squeal. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [June 8, 2025, 8:25pm UTC](https://boards.straightdope.com/t/another-bike-post-brake-question/1019340/5 "2025-06-08T20:25:24Z")
I do not know that you did anything “wrong.” There is a break-in period and maybe you didn’t get the memo on doing that. Some suggestions from Google: - Clean rotors thoroughly with alcohol - Sand pads lightly with fine sandpaper (220-grit) - Clean pad surface with alcohol - Re-bed the system ---
**Author:** ![Reply](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/reply/32/15952_2.png) [@Reply](https://boards.straightdope.com/u/Reply)\ **Post date:** [June 8, 2025, 8:29pm UTC](https://boards.straightdope.com/t/another-bike-post-brake-question/1019340/6 "2025-06-08T20:29:53Z")
I don’t think you did anything wrong. Some bike shops will pre bed the brakes for you and others won’t, and there’s also manufacturing tolerances and installation angles and humidity and dust and such to consider. For me the squeals come and go depending on the individual bike (even two of the same model), season, weather, dust, etc. It doesn’t really seem to affect braking performance, though on an ebike it might be more noticeable than on my pedal bikes. If you’re worried, just take it back to the shop and ask them to fix it. I think they just sand the rotor or discs a tiny bit. ---
**Author:** ![RivkahChaya](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rivkahchaya/32/8919_2.png) [@RivkahChaya](https://boards.straightdope.com/u/RivkahChaya)\ **Post date:** [June 8, 2025, 9:33pm UTC](https://boards.straightdope.com/t/another-bike-post-brake-question/1019340/7 "2025-06-08T21:33:38Z")
I’m capable of cleaning them with alcohol, and I have sandpaper-- also have emery boards. I’ve never bedded my brakes, but this is the first bike is haven’t bought from a shop. ---
**Author:** ![Gatopescado](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gatopescado/32/5711_2.png) [@Gatopescado](https://boards.straightdope.com/u/Gatopescado)\ **Post date:** [June 8, 2025, 10:05pm UTC](https://boards.straightdope.com/t/another-bike-post-brake-question/1019340/8 "2025-06-08T22:05:33Z")
> [@RivkahChaya](#): > > my acoustic bike Uh… what? ---
**Author:** ![Beckdawrek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beckdawrek/32/3647_2.png) [@Beckdawrek](https://boards.straightdope.com/u/Beckdawrek)\ **Post date:** [June 8, 2025, 10:10pm UTC](https://boards.straightdope.com/t/another-bike-post-brake-question/1019340/9 "2025-06-08T22:10:01Z")
Like acoustic guitar. No power? ---
**Author:** ![RivkahChaya](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rivkahchaya/32/8919_2.png) [@RivkahChaya](https://boards.straightdope.com/u/RivkahChaya)\ **Post date:** [June 8, 2025, 10:11pm UTC](https://boards.straightdope.com/t/another-bike-post-brake-question/1019340/10 "2025-06-08T22:11:23Z")
It’s a joke. The original non-electric version of something is called the “acoustic” version, even if it’s not a musical instrument. I see “acoustic bike” all the time. ETA: albeit, a bicycle is used as a musical instrument in a Peter Schickele piece, where they also use a sandwich machine. ---
**Author:** ![Gatopescado](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gatopescado/32/5711_2.png) [@Gatopescado](https://boards.straightdope.com/u/Gatopescado)\ **Post date:** [June 8, 2025, 10:12pm UTC](https://boards.straightdope.com/t/another-bike-post-brake-question/1019340/11 "2025-06-08T22:12:30Z")
> [@RivkahChaya](#): > > It’s a joke. Ah! You got me! 😄 ---
**Author:** ![sb1953](https://avatars.discourse-cdn.com/v4/letter/s/a87d85/32.png) [@sb1953](https://boards.straightdope.com/u/sb1953)\ **Post date:** [June 8, 2025, 10:14pm UTC](https://boards.straightdope.com/t/another-bike-post-brake-question/1019340/12 "2025-06-08T22:14:08Z")
I would use like 220 grit sandpaper on the rotor on both sides that should help the pads “bed” themselves to the rotor. I am still old-school brake on the rim Good luck ---
**Author:** ![The\_Librarian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/the_librarian/32/402_2.png) [@The\_Librarian](https://boards.straightdope.com/u/The_Librarian)\ **Post date:** [June 8, 2025, 11:31pm UTC](https://boards.straightdope.com/t/another-bike-post-brake-question/1019340/13 "2025-06-08T23:31:01Z")
Disc brakes will start to squeal with the slightest (oily) contamination. With slight contamination you can try sanding then down. If you try this. don’t be too careful, and really remove some material. Personally I try to be really careful about not contaminating the pads and when they do pick up something I just replace them. That’s better for the environment and my skin than fucking around endlessly with brake cleaner. ---
**Author:** ![RivkahChaya](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rivkahchaya/32/8919_2.png) [@RivkahChaya](https://boards.straightdope.com/u/RivkahChaya)\ **Post date:** [June 9, 2025, 12:05am UTC](https://boards.straightdope.com/t/another-bike-post-brake-question/1019340/14 "2025-06-09T00:05:05Z")
These brakes are on a bike I just started riding a couple of weeks ago. Don’t remember the exact mileage, but they have fewer than 100 miles on them. I’m not going to replace brakes every 100 miles. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [June 9, 2025, 12:08am UTC](https://boards.straightdope.com/t/another-bike-post-brake-question/1019340/15 "2025-06-09T00:08:25Z")
> [@RivkahChaya](#): > > I’m not going to replace brakes every 100 miles. If your e-bike has regen braking use that as much as possible. Certainly use the mechanical brakes when needed but you can get a lot out of the regen braking. Which, of course, saves your brakes. They last a lot longer (and you get a little more range out of the battery). ---
**Author:** ![wguy123](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wguy123/32/3161_2.png) [@wguy123](https://boards.straightdope.com/u/wguy123)\ **Post date:** [June 9, 2025, 12:12am UTC](https://boards.straightdope.com/t/another-bike-post-brake-question/1019340/16 "2025-06-09T00:12:06Z")
I’ve found that sintered pads squeal and are a lot noisier than organic/resin pads. Since I replace them myself, I go with organic even though they don’t last as long. Biggest reason is I like the feel of them a lot better, particularly on my mountain bike. ---
**Author:** ![Melbourne](https://avatars.discourse-cdn.com/v4/letter/m/b5e925/32.png) [@Melbourne](https://boards.straightdope.com/u/Melbourne)\ **Post date:** [June 9, 2025, 12:23am UTC](https://boards.straightdope.com/t/another-bike-post-brake-question/1019340/17 "2025-06-09T00:23:05Z")
> [@RivkahChaya](#): > > can feel free to recount stories of brake issues Took the coaster brake apart on the rear wheel, cleaned and greased it, but it all back together. Probably because it was squeaking, or had been damp, or needed it for some reason. Wait, did I say **greased** it? Took it for a ride, went back, took it all apart again, carefully cleaned it again, **oiled** it, and re-assembled. ---
**Author:** ![smithsb](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/smithsb/32/12107_2.png) [@smithsb](https://boards.straightdope.com/u/smithsb)\ **Post date:** [June 9, 2025, 12:31am UTC](https://boards.straightdope.com/t/another-bike-post-brake-question/1019340/18 "2025-06-09T00:31:52Z")
At an automotive parts place, they have brake cleaner. Nasty stuff on you or paint so be aware where it goes. If you get new rotors/pads for a vehicle, you have to clean the rotors/pads first. There’s a kind of invisible gunk on them from the factory to keep the rotor from rusting in transit (the gunk melts into a deposit on the rotors making the brake/squeak/break/squeak sound). **Back to the bike** - After a bit of sanding, use the cleaner on both pads and rotors. Do the bedding in again. Accelerate to a moderate speed, moderately apply brakes to a stop. Rinse lather repeat a few times (say 5 or 6). Then do a couple more aggressive stops and you should be set. If they still squeal, see the bike shop for a possible alignment problem. Is the rear wheel is correctly straight in the frame (just asking)? Being slightly offset will cause the disc (on the hub) to misalign with the pads (secured with the calipers to the frame). ---
**Author:** ![The\_Librarian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/the_librarian/32/402_2.png) [@The\_Librarian](https://boards.straightdope.com/u/The_Librarian)\ **Post date:** [June 9, 2025, 7:23am UTC](https://boards.straightdope.com/t/another-bike-post-brake-question/1019340/19 "2025-06-09T07:23:13Z")
Pads last roughly a year(4-5k) on my bike. (Or 1 chain/ a set of tires) I try to cycle year round. In the wet they’ll squeal no matter what. It seems they last longer when I don’t mess around with them.