Caliper not fully releasing??


50 replies to this topic
  • Wyatt

Posted March 23, 2003 - 03:27 PM

#1

I am having trouble with the front brake on my bike. The cliper does not seem to fully release, and the brake will drag. It is sometimes worse than other times.

I noticed this while giving my bike a thourough looking over after a pretty hairy crash. My first thought was a bent rotor, due to the crash. But, I don't feel like this is a bent rotor because it is equally dragging the entire rotation of the tire.

If the bike is on the stand, and I spin the front tire quickly, it will not make much more than 1 and 1/2 turns on its on.

I have removed the caliper and pushed the pistons in by hand, and the wheel spins fine. After I apply the brake, it never fully releases, and drags.

What could cause this?? I have heard of brake lines on cars partialy collapsing and not letting brakes fully release, but i have never run into this prob with my bike.

Just looking for suggestions before I go ripping my caliper apart.

  • cowboyona426

Posted March 23, 2003 - 03:43 PM

#2

Wyatt- did you stick the front end in some deep, loose dirt? I would suspect that there is something in the caliper that won't let the pistons slide like they should. How long since you changed the brake fluid? I have heard that sometimes old brake fluid will cause the pistons to get rusty, which also might make them hang up. I would start there, to me it sounds like you'll need to disassemble the caliper. You didn't scratch your swingarm did you? :)

  • MX813

Posted March 23, 2003 - 03:55 PM

#3

Wyatt,

Two things that I would check first off:

1. Pull the caliper pins out and ensure that there is no rust, residue on it. Buff and clean off if there is.
2. Check your front disc to ensure that it is not tweaked/bent. From your post, you said you were pushing pads out but once brake is applied, there is tension on the disc, it may be rubbing.

If none of these are the culprit, then not sure where to go but listen to other suggestions from fellow TT'ers.

mx813

  • Wyatt

Posted March 23, 2003 - 04:27 PM

#4

Thanks guys.

Fluid is good, and I did pull the pins to check to make sure that it was not binding there.

Yes, it did a number on the swingarm also. Messed it up pretty bad. But, it's fixed already :)

  • cowboyona426

Posted March 23, 2003 - 04:32 PM

#5

So there is truth to the rumor that you actually ride your bike :) Good luck with the brakes :D

  • Bill

Posted March 23, 2003 - 04:37 PM

#6

Look to see if the outside pad (non piston side) is rubbing. If so, check to make sure the caliper pins are straight and clean/lubed. If there bent or dirty, when you apply the brakes, the caliper does not return to a neutral position.

If it's the piston side pad. You have a failing seal or dirty piston. The piston is sealed and return actuated, by the sqaure cut seal on the piston. If the seal is worn (edges rounded). It will not distort enough, to return the piston, when hydraulic pressure is released.

You could also have an obstructed hose. Which is not releasing the pressure, after the brake has been released. You can apply the brake and release it, immediatly open the bleeder to see if there's any residual pressure in the caliper. This would indicate an obstructed hose.

Bill

  • Wyatt

Posted March 23, 2003 - 05:10 PM

#7

Thanks Bill,

Excellent advice on cracking the bleeder to check for residual pressure. I did not think of that. I will also take a close look to see which pad is making contact.

I am not going to look at it tonight, but I will work on it tommorow. I will post back what I find.

Thanks again,
Johnny

  • John407

Posted March 23, 2003 - 06:31 PM

#8

It could also be the piston itself hanging up. I had it happen to my rear brake. The piston had some dirt and small marks on it, pulled the caliper apart and used emery cloth on the outside of the piston it now releases fully again. It must hang up in the seal.

  • Fastest1

Posted March 24, 2003 - 08:12 AM

#9

Wyatt, I have been having this problem for some time with no luck yet!. I have rebuilt the master on the original 2000 twice and the caliper once. I then bought a master off of a 2001 and rebuilt it also. I have great feel in the lever, I am sure there is no air. The pins are straight and clean. There are no leaks whatsoever. Nothing gives I have considered buying a new caliper but during my rebuild of it ,the kit came with new pistons and seals. My original pistons and bore had no marks , scratches, nicks anything. I have run different fluids with no chnge in results. I even called Don Maeda of Dogtown brakes and he is stumped. He said my understanding of the seals and positive retraction were right on and couldnt see why it wasnt working. I have never had a brake problem like this. I have even changed the brakeline one more time after already having a fastline. The caliper is the only unchanged item though it has been rebuilt. If you fix it tell me. I have loosened all of my clamps, triples, lower fork and axle. Good Luck. I can even take the caliper and disc in my hand without being on the bike and it doesnt retract enough to fall off of the disc when I let off the lever. It does loosen some but doesnt fall off nor slip freely. :)

  • Wyatt

Posted March 24, 2003 - 08:30 AM

#10

Fastest,

How much did the caliper kit cost? If it is not too expensive, I may try it.

Did you see my post on the Philips racing Fuel? I know you use it. The name has changed.

I have not had a chance to look at my brake yet today, but i have to get it fixed. The dragging brake has to be glazing the pad and creating mucho heat in the brake caliper.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • John_Lorenz

Posted March 24, 2003 - 09:20 AM

#11

Wyatt
From time to time I have to remove the pads and clean things up in the calipers. I have noticed that the pins get some what corroded and full of dust and crap.

I clean these periodical with a wire brush, grease things up and put back together. I ride in a dusty area and just do the cleaning as general maint.

  • Wyatt

Posted March 24, 2003 - 04:05 PM

#12

Thanks for all of the tips guys.

I took the caliper off again and really gave it a good going over. I cleaned and lubed the pins, and cleaned the bolt that goes through the pads. I also used brake cleaner and cleaned around the piston dust seals.

It does release better, but I am still not convinced that it is right yet. The funny thing is that i cannot remember how easy it turned before.

So, if someone is coon-fingering your bike the next time that you are at the track, don't worry, it is just me seeing how easy your front wheel will spin. :)

My next thing to do will be a caliper kit if I am not satisfied with how it is now.

  • Fastest1

Posted March 25, 2003 - 03:41 AM

#13

The problem is not in the pins! This is definitely a problem with piston retraction. I too am having the same problem. I know that Wyatt maintains his bike meticulously as do I, though he does spend more time polishing :). I did price a caliper thru NCY (North County Yamaha) they were $155.00. I am trying to solve the problem instead of replacement. There are no visible problems with the caliper when I disassemble them. No wear on the pistons or the cylinder bores. The pistons btw are made of a thermoplastic so rust is not an issue. The pistons when lubed thouroughly with brake fluid dont slide in and out as easily as other calipers I have worked on. Your wheel should spin freely when the bike is on the stand. Say at least 5-7 revolutions when you spin the wheel firmly by hand. I get 1-2. Everybody elses I have tried spins freely. It should even rock both directions if you place a small weight on the stem or rim lock much like a bicycle does. The wheel does not drag when the caliper is removed so I know it is not bearings. The front end is aligned with no force needed as nothing is bent. Stumped!

  • John_Lorenz

Posted March 25, 2003 - 04:07 AM

#14

I agree with Fastest1 on this but I also have noticed on my 00 that the front wheel drags a specific points when spinning. It is better when I clean and maintain the Calipers, and make sure all moving parts are free from debris.

At first I thought the rotor was bent, but placing it on a dial Gage proved it was in tolerance. I then though the Caliper itself was miss aligned or the bracket holding it was damaged or bent. Again all in tolerance.

I have noticed my sons 02 250 does not do this, is it the calipers or is it the floating brakes ? or a combo of both.

Personally I think it has more to do with the floating rotor design...

  • Wyatt

Posted March 25, 2003 - 04:55 AM

#15

I think that I may try a caliper kit. I can hear it drag the entire revolution of the wheel. It is simply not releasing fully, and I absolutely hate when things are not right.

It has to be, as Fastest stated, a matter of the pistons not retracting properly. My wheel does not drag at specific points. It drags equally the entire wheel revolution.

  • Fastest1

Posted March 25, 2003 - 07:38 AM

#16

I would have thought it had to do with the floating or non floating rotor also. I replaced my stock rotor with a braking oversized, it is true and is a floating rotor. It did not change a thing also mine doesnt release when I am holding the stock rotor in my hand with the caliper on it. I too have a consistent drag all of the way around not like a warped disc where it touches in spots. I am really debating sending my brakes to Dogtown Brakes for 180.00 with a new line included. I know quite a few mechanics at different bike shops in town and all are baffled. The yz250 has the same front forks, master cylinder, calipers and disc so they should work the same. I have always wondered that upon the initial installation if the brakes were dragging, would the heat be so incredible that it could have distorted something? I replaced everything except the caliper body which is in great condition, still no luck. Hell even my 6 piston Harris calipers on my street bike of which there are 2 sets drag less than this one does.

  • Wyatt

Posted March 25, 2003 - 07:47 AM

#17

I just ordered my caliper kit.

We'll see how it goes.

  • skthom2320

Posted March 25, 2003 - 03:08 PM

#18

So, if someone is coon-fingering your bike the next time that you are at the track ...


Pervert! Stay away from my wheels!

I heard that brakes do that if you ride too slow for too long. :)

  • Wyatt

Posted March 25, 2003 - 03:25 PM

#19

I wouldn't spin the wheel on that roached-out bike of yours anyway. It is probably so far from right that I would think mine is good!!! :)

  • Yz400F_183

Posted March 25, 2003 - 03:33 PM

#20

Hope the Kit Fixes the problem. I hade a problem with my Front brakes but turns out the my disk was bent and Cracked..That what happens when you hit someone 3erd pinned..i couldn't even finsh the race because it knocked me out!





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