B1KE

I have a set of disc brakes and when I get high speeds usually 20-25mph and I apply the brake, I get a loud thudding noise only in the front brake.

Any ideas on what could be causing this?

Note: Rotars are not rubbing on caliper.


Thanks for the help!

dynaryder

Is the wheel fully in the dropouts? Is the headset tight? Are the caliper bolts tight? Is it just noise or do you feel something in the lever?

corrado33

A singular loud thudding noise? Or a repeated loud thudding noise?

Singular: Loose headset, loose front wheel, loose front axle/bearings.

Repeated: That's the noise disk brakes make when you use them at high speeds. Sounds like purring.

Andrew R Stewart 

Another repeating noise could be a rotor with a gauge or burr on it. A singular noise could be the pads moving within the caliper, missing pad spring? Andy.

corrado33

Agree on both points. However, I have some cheap hydraulic brakes that the pads move a bit when I apply the brakes. I wouldn't describe the noise as a "thudding" noise, more of a sharp click.

B1KE

I was recently greasing the headset, I might of hit the pad spring out when I attached the wheel back, what would I look for once I take the wheel out to know whether the pad spring is in the brake pad?

B1KE

What's a gauge/burr and how do I go about looking for one/solving it if I do have one?

B1KE

Additionally the pad noise is perfectly normal in conditions up to 20mph but passed 20mph it makes the loud thudding noise. Hope this might help in the diagnosis.

Andrew R Stewart 

A gauge or burr is a localized deformation of the rotor's surface. A gauge is like a tiny trench. A burr is an edge with a bit of it sticking up. Either could be snagging the pad with each revolution. But from your description I doubt that's what's going on. Some brakes have a sheet metal clip or spring to position or to help retract the pads. It should be easy to find a assembly diagram on line, or just look at the rear brake. Andy.

Klassicbike

One issue I see all too often is noise due to wrong alignment of brake pads to rotor, due to wrong mount added (Ex. change AVID to Shimano) or wrongly set up (washers...). Show us a picture of your affected area.

JonathanGennick 

Was the onset of the noise sudden? Were the brakes working one day and making noise the next? Does any of your maintenance work on the bike coincide with that time?

cobba

A problem with the headset is one of the first things I thought of.

B1KE

What could be the problem? I installed all bearings, greased, tightened everything. Maybe bearings is loose and inserted properly? but then how could that be related to a disc break thudding upon applying pressure on the brake?

B1KE

I'm pretty certain it's a noise from the headset because it's making a thudding noise at low speeds too. What could be loose and what should I check?

I recently removed the headset to grease the bearings.

Andrew R Stewart 

If the headset adjustment was too loose there could be a rocking of the fork within the head tube when the brake is applied. A proper adjustment will allow the fork to rotate freely without binding and also have no slop. By applying the ft brake then rocking the bike fore and aft (when holding the handle bars) a loose adjustment will be felt as a knock as the fore then aft force is applied. As the headset adjustment is bit by bit tightened up the rocking/knock will decrease and just go away as the best bearing preload is attained.

It's hard to tell a too tight adjustment from a good one if the bearings are in good condition. But a too tight adjustment will hasten the bearing's demise by a lot. This is why when teaching how to do a headset adjustment I always tell the student to start with a too loose one. This slop can be felt easily. Too tight isn't.

When riders come into the shop with a problem, a noise or feel a knock sometimes they don't understand why a complete tune up is what we often start the process with. After all the problem is from one source... But this thread has shown that a simple problem can have a number of sources. A general base lining of the bike's adjustments and condition can often find/fix the problem. It can also allow the time and exploration by a skilled wrench to discover other issues that might not have yet been noticed by the rider.

I do wonder if during the headset servicing if the OP got the reassembly correct. If a bearing is placed upside down all adjustment attempts are for naught. Andy.

B1KE

First I greased the headset, put everything back together, went out for a 30 mile ride, brakes and everything were working fine, all of a sudden around mile 15 when I hit the front brake to slow down I started to hear a loud thudding noise. Perhaps the disc mad may have moved out of place?

B1KE

I don't get any play in the headset when I apply the front brake and push it fore and aft, but under sudden stops and harder breaking I do feel a loud thudding noise from the disc brake and feel like the bearings in the headset are making a noise internally.

Is it possible for the entire headset to fit, even if I put the bearings on backwards?

asmac

Would I be right to think that you and the other poster actually mean "gouge"?

Andrew R Stewart 

Yes for my post. I'm a pretty good wrench/fab guy but my parents turn in their graves when I try to spell. Andy.