Another noisy disc brake thread

[glasgowcyclist]

Here you go.

My guess is that the mistakes were:

1) Brake too hard too soon.
2) Came to a complete stop with the brake lever still applied.
3) Not enough gradual stops before braking hard.

Thanks for that. To clarify; I didn't actually come to a complete stop but got down to about 4mph and that's when they started to squeal again so I released the brakes, got back up to speed and repeated. I guess my technique needs to be adjusted to match the info in that pdf.

Incidentally, I'd followed the advice contained in the link in an earlier post:
"Wayne says to break in your disc brakes with a series of very firm stops from a reasonably good speed before you get out on the trail. This properly deposits the pad material on the braking surface of the rotors."

I'll sand the discs again and start over.


GC

 

[Nibor]

If your discs appear to be riveted on they may be Shimano Centrelock discs which slide on to splines at the centre with a locking ring rather like Cassettes

 

[glasgowcyclist]

If your discs appear to be riveted on they may be Shimano Centrelock discs which slide on to splines at the centre with a locking ring rather like Cassettes

Aha! Well spotted, I've just been out to the bike shed and it looks like that's what they are.

GC

 

[Yellow Saddle]

Thanks for that. To clarify; I didn't actually come to a complete stop but got down to about 4mph and that's when they started to squeal again so I released the brakes, got back up to speed and repeated. I guess my technique needs to be adjusted to match the info in that pdf.

Incidentally, I'd followed the advice contained in the link in an earlier post:
"Wayne says to break in your disc brakes with a series of very firm stops from a reasonably good speed before you get out on the trail. This properly deposits the pad material on the braking surface of the rotors."

I'll sand the discs again and start over.


GC

I'm afraid Wayne got it wrong.

You don't want to come to a complete stop because that would then deposit too much material onto the disc during that last quarter of a revolution or so. Also, when you stop and hold the brake, the material deposits underneath the pad in a pad shape. This causes vibration and noise.

The pad material is not fully cured when it leaves the factory and it is the fitter's job to cure it by doing the burn-in/break-in procedure. As I've written previously on this forum, this ignorance of the procedure, even at trade level, is the single biggest spoiler for disc brake advancement. They world well but require very careful handling.

I suggest you sand it again (with the discs off the bike) and start over with new pads. Don't throw the old (new ones you have on there now) away, but use the new ones for the burn-in and then swap back to the old ones who have now already been cured. You need new pads for a burn-in, you can't do it with old pads because they've already cured and outgassed all the stuff that's supposed to coat the disc.

 

[glasgowcyclist]

I sanded the discs more thoroughly (off the bike this time), fitted new pads and followed @Yellow Saddle 's bedding-in instructions. All fine for about ten days then the squeal began to reappear: only towards the very end of braking at first but increasing every journey.

I've found that the only way to keep it from getting worse is to do a mini bedding-in sequence at the start of each ride; otherwise it squeals like a banshee from 8mph. That way it only squeals when I'm practically stopped.

My next option, I suppose, is new discs so I'm looking at a pair of these Shimano SM RT81s:


Do I really need to fork out on yet another set of pads with these?

GC

 

[ianrauk]

Do I really need to fork out on yet another set of pads with these?

What pads are you using?
I find that Semi-Metallic ones are the quietest and less prone to any squeal. Sintered ones are the worst culprit.

 

[glasgowcyclist]

What pads are you using?
I find that Semi-Metallic ones are the quietest and less prone to any squeal. Sintered ones are the worst culprit.

I'm using Shimano B01S pads, my current discs say to use only resin pads.

GC

 

[ianrauk]

I'm using Shimano B01S pads, my current discs say to use only resin pads.

GC

Shimano also used to say not to mix and match components.
Check out Disco Brakes to see if you can get alternatives.

Edit:
Found them. HERE you go. £6.75 a pair in stock.

 

[Yellow Saddle]

I sanded the discs more thoroughly (off the bike this time), fitted new pads and followed @Yellow Saddle 's bedding-in instructions. All fine for about ten days then the squeal began to reappear: only towards the very end of braking at first but increasing every journey.

I've found that the only way to keep it from getting worse is to do a mini bedding-in sequence at the start of each ride; otherwise it squeals like a banshee from 8mph. That way it only squeals when I'm practically stopped.

My next option, I suppose, is new discs so I'm looking at a pair of these Shimano SM RT81s:

View attachment 134674
Do I really need to fork out on yet another set of pads with these?

GC

If you are reasonably sure that the "old" pads are not contaminated, then no, they won't ruin the new discs. However, bedding in requires new pads because when the pads are new, they're still only partly cured and by bedding them in they deposit material onto the disc. If you have a new disc with old pads, they won't deposit material because they are now fully cured. Buy another identical set, bed in the discs with those and then switch to the old ones.

Have I mentioned that discs are a pain?

 

[Yellow Saddle]

Shimano also used to say not to mix and match components.
Check out Disco Brakes to see if you can get alternatives.

Edit:
Found them. HERE you go. £6.75 a pair in stock.

Sintered and semi

What pads are you using?
I find that Semi-Metallic ones are the quietest and less prone to any squeal. Sintered ones are the worst culprit.

Semi-metal and sintered metal is one and the same thing.
There are only two types - resin and sintered. Call it organic and metal if you like.
Some people will now have the urge to mention ceramic pads but they are just a sintered pad with different "stuff" inside, including a bit of ceramic.

Most people will also tell you that sintered metal pads are the noisiest.

 

[glasgowcyclist]

If you are reasonably sure that the "old" pads are not contaminated, then no, they won't ruin the new discs. However, bedding in requires new pads because when the pads are new, they're still only partly cured and by bedding them in they deposit material onto the disc. If you have a new disc with old pads, they won't deposit material because they are now fully cured. Buy another identical set, bed in the discs with those and then switch to the old ones.

FFS! That'll be the third set of pads in 6 weeks!

Have I mentioned that discs are a pain?

And costly.

I fitted discs to my old Trek Fuel 80 a good few years ago and they've never given me a hint of this bother, and I've never gone through any bedding-in sequence with those. It's quite a puzzle.

GC

 

[Crackle]

I've done all this, honestly get the Superstar resins.

 

[jowwy]

Cant believe so many people are having issues with discs......i have found them pretty simple to setup and use, have had no squealing and have never used any breaking in procedure

 

[ianrauk]

Cant believe so many people are having issues with discs......i have found them pretty simple to setup and use, have had no squealing and have never used any breaking in procedure

Me too.

 

[fossyant]

Me too.

Snap. Kids both have mechanical discs and I've just got hydraulic discs. No issues with setup or squealing. The only noise I get is when the brakes haven't been applied for a bit and they are covered in mud !