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Discussion Starter · #1 ·
Folks - wondering if anyone can help with a strange issue that I'm having

My front right brake is making a weird thumping sound when I depress the brake 50% of the way down at speed.

I took it into the mechanic and the think its just something created by friction and can't see a mechanical cause. However, I have the same Praxxis Deluxe pads and Drilled / Slotted rotors on all 4 wheels and not happening anywhere else.

Thanks in advance!
Chip
 

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Thumping sound once brake is depressed....does it sound like it happens with every revolution? Could it be:
a)warped rotor
b)oddly worn pad
c)loose pad
Do some preliminary stuff....spray brake quiet on the back of the pad. Take them off, inspect and then retighten so you KNOW that it's done right. If it still persists, then you can look into a warped rotor (maybe swap with a buddy to test another one)
 

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If you feel it in the pedal, it's likely a cracked, warped, or non-constant-thickness rotor. It takes less than a thousanth of an inch of thickness variation to do that.

If it thumps but you DON'T feel it in the pedal, it's probably hard spots (smoothness variation), glazing, or rust on the rotor.

In either case, new rotors are the best solution. It's very difficult to correct these problems permanently (they often recur after a short time) by turning the rotors, and new rotors are not very expensive.

Drilled or slotted rotors are more prone to these types of problems than plain ones.
 

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Discussion Starter · #9 ·
swcrow17 said:
Thumping sound once brake is depressed....does it sound like it happens with every revolution? Could it be:
a)warped rotor
b)oddly worn pad
c)loose pad
Do some preliminary stuff....spray brake quiet on the back of the pad. Take them off, inspect and then retighten so you KNOW that it's done right. If it still persists, then you can look into a warped rotor (maybe swap with a buddy to test another one)
No, doesn't happen every revolution - just when the brake is first depressed. When you release it fully, the repeat - that's the only other time you hear the thump
 

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Discussion Starter · #10 ·
DaveW said:
If you feel it in the pedal, it's likely a cracked, warped, or non-constant-thickness rotor. It takes less than a thousanth of an inch of thickness variation to do that.

If it thumps but you DON'T feel it in the pedal, it's probably hard spots (smoothness variation), glazing, or rust on the rotor.

In either case, new rotors are the best solution. It's very difficult to correct these problems permanently (they often recur after a short time) by turning the rotors, and new rotors are not very expensive.

Drilled or slotted rotors are more prone to these types of problems than plain ones.
I guess the good news is that I don't feel it in the pedal - just hear the noise (pretty prominent).
 

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igolfchip said:
No, doesn't happen every revolution - just when the brake is first depressed. When you release it fully, the repeat - that's the only other time you hear the thump
This changes my diagnosis - if you only feel it when first applying the brakes, it's probably something loose (suspension ball joint or bushing, caliper, pads themselves, etc.) that is shifting and thumps when it reaches whatever stops it. The rotors are probably OK.
 

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DaveW said:
This changes my diagnosis - if you only feel it when first applying the brakes, it's probably something loose (suspension ball joint or bushing, caliper, pads themselves, etc.) that is shifting and thumps when it reaches whatever stops it. The rotors are probably OK.
I'm with you. I think my first stab in the dark guess could be right. It could be your caliper guide pin bushings. It could be some part of the suspension but then I would think you would hear the thump at other times when your not using your brakes. Do you ever hear it when you are not using your brakes? If everything really is tightened up and secured properly, I would try replacing your caliper guide pin bushings.
 

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DaveW said:
This changes my diagnosis - if you only feel it when first applying the brakes, it's probably something loose (suspension ball joint or bushing, caliper, pads themselves, etc.) that is shifting and thumps when it reaches whatever stops it. The rotors are probably OK.
I have to agree with this. It is entirely possible that a bad ball joint or loose part is making this sound. It may not be as noticeable while driving.
 
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