Shimano LX - Sticky Brakes?

[Juan]

hi,

 

Its very wierd. The front brake is fine and feathers great but for some or other reason the back brake sticks about half way through the "pull" of the brake.

 

Its quite irritating. You'll pull the brake right up to the point where it sticks and by this stage the brake isnt slowing the bike down at all even at slow speeds. Then you'll pull it through the sticky bit and... the back wheel locks!

 

I've tried cleaning it with a spirits based (dirt bike type) brake pad cleaner but that only works for about a half an hour and then its back to the same story.

 

has anyone got some advise for me?

[Dirtbreath]

V or disc brakes? Try sanding the pad. There is often some grit that only sanding will remove. Clean the rim/rotor as well.

[shaunh]

sounds like a sticky subject to me!!!

[Juan]

its Hydraulic discs.

It even does is with the wheel off the axel. Is it possible for dirt to get in behind the actual moving part in the caliper?

[Canaris]

where to look:

 

is the hydraulic system still good?

have you been touching the disc with your fingers?

is the disc bent?

have you crashed recently and damaged the break lever?

are you pads unevenly worn?

are the aligned to the disc?

 

again, have you crashed recently?

do you take the rear wheel off when transporting your bike?

 

[Juan]

where to look:

 

is the hydraulic system still good? Yes, there is no damage to the tubes etc. the hydrolic fluid perhaps?

have you been touching the disc with your fingers? Yes...

is the disc bent? No.

have you crashed recently and damaged the break lever? No

are you pads unevenly worn? Yes, and still lots of meat on them.

are the aligned to the disc? Yes.

 

again, have you crashed recently? No

do you take the rear wheel off when transporting your bike? No, the whole bike goes on a rack. With no other bikes touching it.

 

 

[Canaris]

Juan, the only possible suggestion I can come up with is a dreaded airbubble has found its was into the system, and this may explain the sticky reaction.   But I am not SME (subject matter expert).  Rather wait for dirt rider to give answers on this.  What does your LBS say?

[Juan]

Thanks KonaFan,

Much appreciated. Will re-bleed the system and see if it works. My LBS cleaned it and said "that will do the trick".

 

thanks again, hopefully i'll get a reply from Dirt Rider.

[Johan Bornman]

The symptoms you describe don't correlate with air in the system. Air in the system presents as a brake that initially bottoms out and then with pumping firms up.

 

I would also eliminate a bent disk or contamination on the disk itself. This presents as a pulsating feeling when you brake.

 

Check the pistons for smoothness by doing the following.

 

1) Remove the rear wheel

2) Find A large flat screwdriver somewhere.

3) Put the screwdriver where the disk would go and twist it sideways so that the pistons are opened.

4) Now call someone to come and operate the brake.

5) See if you can easily and smoothly make the pistons return after each application of the brake, by twisting the screwdriver.

 

If this is smooth and trouble-free, we'll think of something else, we know there's no rubbish jamming that mechanism.

 

Also see if this does the same with another wheel. We have not enough info here yet to give you a diagnosis, but stick around, there's some good brains and lots of experience here. 

[Canaris]

The symptoms you describe don't correlate with air in the system. Air in the system presents as a brake that initially bottoms out and then with pumping firms up.

 

I would also eliminate a bent disk or contamination on the disk itself. This presents as a pulsating feeling when you brake.

 

Check the pistons for smoothness by doing the following.

 

1) Remove the rear wheel

2) Find A large flat screwdriver somewhere.

3) Put the screwdriver where the disk would go and twist it sideways so that the pistons are opened.

4) Now call someone to come and operate the brake.

5) See if you can easily and smoothly make the pistons return after each application of the brake' date=' by twisting the screwdriver.

 

If this is smooth and trouble-free, we'll think of something else, we know there's no rubbish jamming that mechanism.

 

Also see if this does the same with another wheel. We have not enough info here yet to give you a diagnosis, but stick around, there's some good brains and lots of experience here. 

[/quote']

 

thanks Johan, good advice, I knew I could count on someone.  What about Mud dee?

[Speed Devil]

If you have air in the system the brake lever will feel very spongy and I doubt that you would be able to lock the brake if that was the case.

 

It could be that you have dirt between the piston and body. Check to see if the piston is travelling straight in and out. It could be that you have some wear and the piston pushes skew when you apply the brake. Take the wheel out and remove the disk pad to get a better view of the piston. get someone to pull the brake while you look at the piston travelling in and out.

 

Speed Devil2008-08-08 08:16:07

[Juan]

Hi Johan,

Thanks you guys are legends! I took the pads off and cleaned them as well as the little brass spreader plate.

 

It now works beautifully! Will test it thoroughly on my ride tonight.