Answered Help needed - rear brake squealing like a Foghorn and vibrating.

[R120]

So after about 20 miles into my maiden outing on my new E-Sentier hardtail this morning, and having though i had beded in the brakes on a quick ride last night, the rear brake started squealing badly, like a foghorn, and sending a lot of vibration through the bike. No idea why, and never had this problem before. Bike is an E-Sentier Hardtail, with Guide RE's. Any help appreciated as at this point i am thinking of just getting a new rotor.

 

[R120]

So went out again followed SRAMs bedding in procedure off their website, and still fog horning and vibrating

Going to try the copper paste tomorrow, but the wheel spins freely and everything appears true. If that fails off to LBS

One thing I have noticed is that the rear brake lever does not return as quickly as the front, or the levers in my Sommett which has the same brakes.

Basically the other levers all spring back instantly but the fog horn brake is a bit slower, almost like there’s a bit of resistance to it

 

[ElectricGuv]

Squealing only when braking?

 

[R120]

Yes, when applying anything other than light pressure to the lever

 

[Witte300]

You may want to google sram sticky piston/sticky lever.
When this is the problem your lbs will warranty replace the brake.

 

[Re-Cycle]

I take it you are sure the rotor isn't bent?

What I do when mounting a 6-bolt rotor on a hub is this:
- screw in all the bolts, but don't tighten them.
- then "turn the disc clockwise", to take up any possible play, and while holding the disc this way tighten the bolts in a cross pattern. Handtight will do.
- use a torque wrench to tighten the bolts to the specified torque, again in a cross pattern. I usually do this in two steps (first 2Nm, then 4Nm).
This way you eliminate possible play in the direction the caliper holds the disc. And play can cause noise
By tightening in two steps in a cross pattern you avoid possible tension in the disc.

Ofcourse you need to be very precise in adjusting the caliper as well. Many people use the method of holding the brake and then tighten the caliper bolts, but that's not the best way. Hope has a video about it, but their method works with every brand.
Because you've got Sram/Avid brakes they can be adjusted in a vertical plane also, so it's important that is done right.

There is no guarantee this will solve your problem, but you will eliminate some possible causes.

Good luck!

 

[Wiltshire Warrior]

It wouldnt hurt to swap the calipers over front to back - yes you would have to learn how to bleed your brakes (this is a good thing) and then you could rule out the sticking piston.

Also have you tried just swapping the pads front to rear?

 

[Donnie797]

Or.... buy Shimano Zee or Saint brakes and be happy

 

[R120]

Or.... buy Shimano Zee or Saint brakes and be happy

May come to that but I have had several sets of guides with no issue before

 

[davegixer]

May come to that but I have had several sets of guides with no issue before

Can’t you get it back to the shop, as it’s so new?

 

[R120]

Nope as its from CRC - My LBS who i have a good relationship with are going to give it a once over, i am beginning to think its the claiper/lever at fault

 

[thebarber]

Email crc, they'll tell you t take em t lbs and get a Price to sort & reimburse you.

 

[R120]

I took out the FS Sommet out for a ride when i got home today, and when i got back i decided to take the Sentier out round the block to see if any magic mechanical wizard had secretly been into my garage overnight - did a couple of laps and what do you know it wasn't really squealing, only a bit when close to locking up.

So i decided to go back and get my helmet, and take the little fecker out for a proper thrash, and ended up riding her like i haven't really riden a hardtail since i had a DJ bike back in the noughties, full pelt and treating every little bump and curb as an excuse to launch it throwing skids and slashes like i had a lifetime supply of Maxxis, and sure enough the squealing had pretty much disappeared by the end of the hour.

Perhaps she decided to behave when i arrived at the local skatepark, the graveyard of many a bike! For the record EMTB's are surprisingly fun in a skate park, thought the BMXers getting high on the benches did give me some odd looks.

Hopefully this is the end of my woes!

 

[Northumbrian]

I had same problem, same bike, my mate also has same problem, same bike !........looks like the larger disc 200mm with larger adaptor is creating the problem.
Biggest improvement I made was removing the tie wrap holding the hydraulic pipe to the chain stay....reduced by about 80% couldn’t believe it!
Next I’m going to try a smaller disc set up, and keep the 200mm rotor as a spare for the front........
Anyone tried this yet?

 

[Donnie797]

I had same problem, same bike, my mate also has same problem, same bike !........looks like the larger disc 200mm with larger adaptor is creating the problem.
Biggest improvement I made was removing the tie wrap holding the hydraulic pipe to the chain stay....reduced by about 80% couldn’t believe it!
Next I’m going to try a smaller disc set up, and keep the 200mm rotor as a spare for the front........
Anyone tried this yet?

Removing that tie wrap helped that much? That's strange, but very good!

But putting on a smaller disc to fight the squealing to me feels like the wrong solution. If the squealing is surely not caused by any loose bolts (and the vibrations that causes) or contaminated disc or brake pads, i would consider swapping the whole brake to a brand that is less known for squealing than SRAM is.

 

[Donnie797]

Oh, just read this neat "hack" from @Swissrob - maybe it is worth a try

 

[Northumbrian]

Removing that tie wrap helped that much? That's strange, but very good!

But putting on a smaller disc to fight the squealing to me feels like the wrong solution. If the squealing is surely not caused by any loose bolts (and the vibrations that causes) or contaminated disc or brake pads, i would consider swapping the whole brake to a brand that is less known for squealing than SRAM is.

It’s not a squealing sound, but a horrid vibration, I think caused by a powerful brake / big rotor, add to this the adaptor is tall I think 60mm tall......as an Engineer all adds up to igreater opportunity for resonance.
Watch this space !

 

[R120]

As an update, the problem persisted again once the brakes got hot.

I have now resolved it by downsizing to a 180mm rear rotor, and the issue has totally gone, and no noticeable difference in power. I posted about it in another thread but forgot to update here

Basically IMO the 200mm disc was putting too much force through the frame, due to the mount putting the calliper so far from the frame fixings. If you lock the rear brake and rock the bike you can see the 200mm adapter mount flex, but with the 180mm it doesn't.

In effect the brake is shifting the mount when applied, causing the vibration - the squealing is from the vibration, not vice versa.

In the end me and the lbs tried two completely new rotors and sets of pads with the 200mm, stripped down the calliper, bled brake, etc etc to no avail, and it was my trusted LBS mechanic who said he thought it was the size of rotor, and showed me the flex.

Because its a hardtail the force all goes into the frame causing the vibration. My instinct here is that Vitus got a job lot of 200mm for the Sommett, and then just used them on the Sentier too, without really thinking about it.

 

[R120]

I had same problem, same bike, my mate also has same problem, same bike !........looks like the larger disc 200mm with larger adaptor is creating the problem.
Biggest improvement I made was removing the tie wrap holding the hydraulic pipe to the chain stay....reduced by about 80% couldn’t believe it!
Next I’m going to try a smaller disc set up, and keep the 200mm rotor as a spare for the front........
Anyone tried this yet?

Taking the tie off/loosening it actually makes sense as when the mount flexes it was probably fighting the movement

 

[Gary]

Have you cleaned and grease between the mount and frame, greased bolt heads and threads and done it up proper tight?
Have you tried your Sommet rear wheel in the Sentier? (will eliminate the disc from the equasion completely if the Sommet wheel is also noisy)
When aligning the caliper. One of these very simple tools works great for alignment and pad spacing.
Wiggle | Birzman Clam Disc Brake Gap Indicator | Workshop Tools
you could make something similar but unless you're in a hurry why bother at that price?

 

[R120]

Everything you mention and more, Sentier wheel and disc in Sommett, no squealing/vibration, Sommet wheel in Sentier, starts squealing.

 

[Gary]

Though you would have. You're usually pretty thorough.
got a pic of the mount?

 

[R120]

No, but suppose i can get off my ass and take one tomorrow

 

[Gary]

it's ok. There's a mega close up on CRC.

I just wanted to see what adapter set-up it uses and if there is a beefier option.
Having just seen it's IS to Post mount. There should be.
Now trying to remember which mounts were hte beefiest is the difficult bit

 

[Donnie797]

It’s not a squealing sound, but a horrid vibration, I think caused by a powerful brake / big rotor, add to this the adaptor is tall I think 60mm tall......as an Engineer all adds up to igreater opportunity for resonance.
Watch this space !

Agreed, but many many bikers do this and don't get noisy vibrations from it, so i wouldn't take that as "normal". On my other bike i've upgraded my discs from 180mm Deore to 203mm XT (2 compound), added the needed adapter from Shimano and switched the whole brake-system from crappy Deore to strong Shimano Zee (using sintermetallic Shimano brake pads) and there are no noisy vibrations at all.

 

[R120]

Agreed, but many many bikers do this and don't get noisy vibrations from it, so i wouldn't take that as "normal". On my other bike i've upgraded my discs from 180mm Deore to 203mm XT (2 compound), added the needed adapter from Shimano and switched the whole brake-system from crappy Deore to strong Shimano Zee (using sintermetallic Shimano brake pads) and there are no noisy vibrations at all.

Is it a hardtail though? This issue relates to the fact is a hardtail, and how the forces etc are being transferred into the frame - you can feel the vibrations though the entire frame and thought the bars. Its a particular issue to the E-Sentier, and not a generic brake problem. The noise is coming from the frame, not the brakes.

 

[Northumbrian]

Is it a hardtail though? This issue relates to the fact is a hardtail, and how the forces etc are being transferred into the frame - you can feel the vibrations though the entire frame and thought the bars. Its a particular issue to the E-Sentier, and not a generic brake problem. The noise is coming from the frame, not the brakes

Correct..... and like yourself I have downsized at the back, down to a 160mm ( I had an Avid disc and adaptor available in the shed) and it is sorted....
IMO, there is no need for a 200 rear, it’s to powerfull for the h/t frame. ( and from an Engineering view, the 200 over time could damage the frame due to the resonance going up through the chain and seat stays)
So the 160 is not as powerful but still capable of locking the rear and being much more progressive , giving better control.
So,
Cleared some spares from the shed,
Gained a spare 200mm fr disc,
Got a more progressive, lighter and better looking rear brake set up.
And...... “no horrendous noise / vibrations”
“Win Win, me thinks....

 

[Donnie797]

Is it a hardtail though? This issue relates to the fact is a hardtail, and how the forces etc are being transferred into the frame - you can feel the vibrations though the entire frame and thought the bars. Its a particular issue to the E-Sentier, and not a generic brake problem. The noise is coming from the frame, not the brakes.

Uhoh, no mine is a full-sus. We were talking about a hardtail here? Sorry, i didn't get that - forget what i said ^^

 

[R120]

So here is a video of the noise it was originally making - doesn't really do it justice as filmed on an iPhone.


I have also attached picture of the new 180mm rotor. There is also a picture of the rear brake hose, you can see from the marks on it where it was being "pulled" against the tie mount by the movement of the calliper mount.

 

[Gary]

So it was flex in the 200mm mount?
Has the 180mm mount/disc solved it?

 

[Northumbrian]

So it was flex in the 200mm mount?
Has the 180mm mount/disc solved it?

I think a number of factors involved ( as already mentioned) but IMO the adaptor was part of the problem.
Ny situation, fittings a 160mm disc sorted it
Patreon’s situation, fitting 180mm disc sorted it
Summary, 200mm disc is a no no on the Sentier.

Sorted