Disc brakes grabbing - help.

[Furbz]

So i have made the move to a disc brake road bike and absolutely love it.

however i have an issue with the front brakes starting to be grabby and squirrely.

 

to better explain the issue: under soft braking all is 100%.

as soon as a brake harder the brakes start gripping and releasing as well as making a squirrely squeaking noise.

its a bit un-nerving as it makes modulating coming to a stop difficult.

 

i have tried the following:

• i removed the pads and cleaned them with a toothbrush and acetone. i then very lightly sanded the pads smooth with 320grit sand paper. a rinse in water and popped them back in. they looked like brand new pads again after this.
• i also used acetone to clean the disc
• the pads have plenty life left in them - i'd say 1mm or more and are flat without surface scratches.

after the above it had to re-bed in the brake pads.

for 50 odd KM it was smooth sailing with good brake performance and noiseless bliss!

but it soon all reverted back which has left me scratching my head.

 

does anyone have a tried and tested options i could look into?

 

[DR ◣◢]

Do you know what compound the pads are?

[madmarc]

From your description it sounds like your rotors have high spots or are slightly bent - Spin the wheel and check for side to side movement.

[Furbz]

i have sram red axs.

i'm 100% certain they are sintered brake pads

[Furbz]

From your description it sounds like your rotors have high spots or are slightly bent - Spin the wheel and check for side to side movement.

 

good call.

i should have mentioned this.

the disc are perfectly true.

 

the entire groupset is only 2000km old

[Jehosefat]

Try sanding the discs as well. Sounds like they might have an uneven buildup of pad material on them. Also make sure there are no small burrs around the ventilation holes in the braking surface.

 

Personally I've had better results from a slightly coarser sandpaper (like 200 grit) rather than the finer stuff.

[MudLark]

Clean the disc and pads with automotive brake cleaner. If that does not work, try replacing the pads altogether.

[JacBrand]

Bed the pads in again. From about 25km/h brake hard, and as soon as the bike stops release the brake. Spray water on the pads and repeat 5-10 times. The repeat will be noisy.

[RaymondC]

Also make sure the disk's and calliper are on properly. Any bolt that's slightly loose could cause this.

Sounds far fetched but I have taken part the system, copper slip on the bolts... no noise.