Jump to content

Help: Front Brake caliper locking up - TTR-125LE

By Chevy Muscle,
in TTR

 Share

Recommended Posts

Apprentice

Chevy Muscle

Posted
Posted

Here's the deal:

Bought a used '03 TTR-125LE about a month ago. It's for my daughter.

Took her riding and after about 3-minutes of riding the front brake pads start to tighten up on the rotor. This is through normal riding and using the brake to slow down. Soon later it gets so tight that it locks up the front wheel.

I took the caliper off and it seems the pistons are extended all the way out and not going back in when the brake is released.

I used some clamps to force them back in and put it back together and it was fine again in the driveway.. Pull the brake and it stops and relase and its fine.

Took her out riding again and the same thing happend after a few minutes of riding.

I took it back apart, released the blead-screw and pushed the pistons back in again and then re-filled the brake fluid and blead the brakes. Seemed fine again until I took it out riding again yesterday. Same thing,... I ride it for a few minutes using the brake normally and then it starts locking up.

Note: When the brakes are locked the lever is real hard when you first start pulling it. I *think* this means that the plunger is not stuck (as it would seem to me that the lever would be soft at first and then hard when almost all the way in). I also *think* that somehow the calipers are over-adjusting themselves too far tight.

Please suggest what to do.

Link to comment
Share on other sites
Veteran

ProCycle

Posted
Posted

Sounds like the adjustment screw at the brake lever is screwed in too far.

There should be a bit of freeplay before the lever touches the plunger

in the master cylinder.

With no freeplay the fluid can't flow back into the reservoir as it heats up and expands.

Link to comment
Share on other sites
Apprentice

Chevy Muscle

Posted
  • Author
Posted
Sounds like the adjustment screw at the brake lever is screwed in too far.

There should be a bit of freeplay before the lever touches the plunger

in the master cylinder.

With no freeplay the fluid can't flow back into the reservoir as it heats up and expands.

That sounds logical. And, you were right.... there was NO free play in the leaver. I had to screw in the adjuster about 1/8" to get some free play.

I hope that was the problem. I'll have to take it back out and try it again now that there is some free play. I have my fingers crossed, but if anyone has additional ideas, I'd like to hear them too.

Another Note: The brake would be locked up, but later one (after checking it about 1-2 hours later, the brake would not be as tight.... still tighter than it should be but not as bad. Maybe that confirms the heating of the fluid causing part of the symptoms.

Link to comment
Share on other sites
Collaborator

o4hondacrf230

Posted
Posted

I dont wanna sound like a smart a@@, but, the same thing happened to my friend. We tried everything, so finally we took the caliper off (2003 KTM SX125) and kept riding. After bleeding and playing with everything nothing seemed to work, until we realized that dirt build up on the front brake lever forced the lever inward (mud built up from a crash) and kept it there. Try cleaning it out real good. If it doesnt work at least its real clean and it didnt cost a thing. lol good luck ed

Link to comment
Share on other sites
Grand Master

enduro4231

Posted
Posted

due to much experience with DH mountain bikes (hydraulic brakes galore) i bet you have a cracked/rotted/worn/blown piston seal. there is a rubber seal that retracts the piston back into the caliper if the brakes are a closed system. if it is an open system, i have no clue. did you get oil or brake fluid on /in the caliper by chance? that would cause the seals to swell up, causing the piston to not fully retract. disassemble the caliper, if you are up to it, and check the seals around the piston. then replace if needed, reassemble, and re-bleed.

Link to comment
Share on other sites
Apprentice

Chevy Muscle

Posted
  • Author
Posted
Sounds like the adjustment screw at the brake lever is screwed in too far.

There should be a bit of freeplay before the lever touches the plunger

in the master cylinder.

With no freeplay the fluid can't flow back into the reservoir as it heats up and expands.

I just wanted to thank you guys and this board. This was the problem.... brakes great now... and then releases :D

Link to comment
Share on other sites
  • 5 years later...

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

ThumperTalk

Register a new account Sign In Now
 Share
Go to topic listing
×
×
  • Create New...
Terms of Use
Copyright
Privacy Policy