Disc brake squeal/vibration

Hi all

I’ve got a 36 Oracle and the brake it came with (tektro Auriga sub) is playing up big time: when the brake is applied it hums and vibrates the whole unicycle. When I first got the Uni a few months ago I contaminated the original brake pads and rotor with oil. It started squealing quite a bit so I cleaned everything with a bit of soapy water… ( I didn’t do a proper clean back then). It wasn’t very quiet but it still worked without being too much of a nuisance. A few weeks ago after a big downhill it really started to vibrate (when used) so badly that I couldn’t use it at all. I am clueless about disc brakes (or any other for that matter) so I have followed advice from this forum and the internet: I have now installed new brake pads (‘jagwire’ brand), sanded the rotor a bit and also cleaned it with a disc brake cleaner spray. It works well for the first few miles, whilst the road is mostly flat, but after I have finished going down a steep hill, and therefore have used the brake a lot, it slowly starts humming and vibrating the Unicycle more and more each time is used. It gets so bad, that each time I go out I have to sand the pads down and clean/sand the rotor a bit so I can use it smoothly for a few miles before the pads get glazed again and the vibrating starts. I have adjusted the position of the calliper/brake pads many times and checked that the D brake/and bearing holder’s bolts are tight enough… I’m guessing this is not normal at all (I thought the disc brakes where easy to maintain and pretty much fool proof) and that they shouldn’t get so glazed after a steep downhill?.

I haven’t got a clue about brakes, I am aware that the cause could be anything (rotor, calliper,…). Is it worth trying a different set of pads (maybe organic?). I wonder if it wouldn’t be just easier, or even cheaper, to start from zero and buy a new rotor and calliper and see how it goes .

Has anyone have had a recurrent similar problem with their disc brake on their 36? is there a disc brake you would recommend that is compatible with the Oracle 36? (not sure if they all have enough clearance for the crank vs calliper when fitted…

Any advice most appreciated :slight_smile:

Some brake rotor/pad combo’s are really loud. It sounds to me like you have a set that don’t play well together. Do you know if the Jagwire pads are the same composition as the Tektro ones you originally had? Have you tried soaking your original pads with brake cleaner, and letting them dry completely before trying them? It could be that you just didn’t get all of the oil out of the pads, and that it was causing the squealing noise.

Changing the pads should help. Organic pads generally quiet the brakes, but wear much faster. Also, some rotors are notoriously loud, which on a bike is annoying, but on a Uni I could see how it would cause the whole machine to vibrate.

Since you said you know nothing about disc brakes I’ll elaborate:

From your description it sounds like it is all quiet and okay when everything is new (or newly cleaned). This is when the rotor hasn’t been embedded with pad compound. Until the rotors are bedded in the brake effectiveness is low, and as the pad beds into the rotor the brakes work better and better due to increased friction between the pad and the embedded material in the rotor. It’s the increased friction that is causing the vibrations you are getting after you have braked a lot.

You are describing exactly what I get on my Oracle 36er…I just put up with it lol :wink:

Interested to see what the people in the know say though. Maybe I’ll sort mine out too!

Thanks a lot for your info Jtrops. I understand now a bit more how the disc brake works.:slight_smile:

I did try cleaning the original pads with the disc brake cleaner and I also sanded them down but it only worked for the first few miles, afterwards back to the vibrations :angry:

Thought a new set of pads would be a fresh start and would make the problem disappear. Not sure what the composition of the Jagwire set is compared to the originals, according to the seller the Jagwire feature a , high performance yet low noise semi metallic compound…

Will definitely try an organic set next week, as even if they wear down quicker, anything is better than the whole uni vibrating like mad. :astonished:

Juni, sorry to hear that you are already getting a similar problem with your Oracle. I thought mine was because I contaminated the brake system with oil from the beginning.

If I didn’t have so many steep hills around here and was just noise I would probably put with it (which I did untill now) but, at the moment, once starts vibrating I find quite dangerous to use the brake going downhill when cars are overtaking me etc…

When you sand the rotors you effectively remove the embedded material, and are starting from scratch again. So, did you clean the pads, but leave the rotors alone? If so, I would say that you have a mismatch between rotor/pad, or that the rotors are just loud.

Do a little searching on your rotors to find out if this is a common problem. Other cyclists may have found quieter rotors for the tektro brakes, or other pad compounds that fix the problem.

Hi Jtrops

Thanks again for your answers. I am getting to understand how it works much more now. As well as the pads I did also clean/sand the rotors.

One question: If I get a new rotor, are they most of them compatible (I guess the quesion is if they all have the same thickness) with different caliper brands? (in this case any disc rotor with the Tektro caliper)

They probably need some breaking in, or the brake needs to be adjusted. To do that, you loosen the two bolts holding the caliper to the frame a little bit, you spin the wheel a little and you brake, hard. You hold the brake and at the same time you tighten the caliper.
Doing so makes sure the caliper (and therefore the pads) is properly aligned with the rotor.

Hi Pierrox.

Thanks for the advice.:slight_smile:

I’m afraid I already follow those steps to align the caliper so I’m guessing they must be more the less aligned.

That is a top tip Pierrox! I didn’t know about setting brakes like that :roll_eyes:

Thanks very much…I’ll be setting my brakes properly, after work tomorrow :slight_smile:

As long as you match pad material to the rotor’s the caliper can be used with just about any rotor. I don’t mean to make it sound like the pad compound is that particular, but certain rotors are not happy with the wrong compound. Rotor width is fairly standardized, and the self adjusting function of hydro calipers ensures that you will have the right clearance regardless of thickness. This is how they continue to have good lever travel even after pads, and rotors wear significantly.

The only thing that I’m aware of that would make a rotor incompatible with a caliper is if it’s an odd size that you can’t get a suitable adapter for. What I mean is that some brands make 200mm rotors, and others are 203mm or 205mm. All of these are essentially the same size, but depending on your caliper you may not be able to get a mount to mix brands that are slightly different. A lot of the time you can make up the difference with washers, but it can be a pain to get it right.

I don’t have one of these disc brakes and I haven’t seen one up close, but I have an idea. Maybe it would work or maybe it wouldn’t apply here. Get some disc brake quiet compound for automotive applications and apply it behind the pads where it would be applied on a car. Sometimes disc brakes just like to squeal or chatter and this stuff works.

I’ve actually had luck in the past (on a bike) putting masking tape on the back of the pads.

But in the end, on my unicycles I’ve found that they usually just need broken in. The first few rides you think they’ll be loud forever until they just seem to stop.

Thanks for the explanation Jtrops, that helps a lot. Much appreciated. :slight_smile:

Will order some organic pads first and if they also squeal like crazy will try replacing the rotor and see how it goes.

That would be great if the vibrations just disappear! You might have a point there.

This is what I was getting at with the comment about cleaning the pads, but leaving the rotors alone. It’s important to properly bed in the rotors, but glazed brake pads can be a problem. Sanding the glaze off of the pads, but leaving the rotors alone can work wonders.

My TRP Spyre squeaked for a while when new and I kinda liked it. It’s quietened down now. I then started noticing more vibration at super low speed maximum threshold braking- think a 36"er going down a 10%+ grade at 3-4 mph. No biggie overall and I’m gaining confidence going down steep declines at (slightly) higher speeds. This has helped with my shudder.

Anyways- my thought on the vibration issue is… There’s some crazy (and a few bad ass dangerous) rotor designs with all kinds of cut outs in the area where the pads contact. Maybe certain designs and spacing of the holes on some rotors are more prone to resonance as we one wheelers use them. Most disc/rotor combos were designed (or at least tested) on bike applications.

Maybe try a different rotor design.

Also,could air in a hydraulic brake system as the OP has cause a modulation problem? Maybe a check of fluid level and a bleed might help.

Rotor design can certainly contribute to the problem. I don’t think bleeding the brake will help at all. A bad bleed, or air in the line, will cause the brake to feel soft and spongy.

to eliminate vibration of the d’brake, you could try Hugos solution. With this setup he successfully eliminated any noise and vibration.

Got it now. :smiley: Didn’t realise does what you meant.

Will keep that in mind. Thanks again :slight_smile:

That is really nice! I think we miss a lot be not being able to understand what’s being posted in the other language forums. I wonder if someone who speaks German and English could translate his write-up? :slight_smile: That would be very cool! (I don’t run a disc brake, but I like seeing things that are imaginative and that work well.)