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Front Brakes Locked!


Amarrache
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Not sure if this is the right area of the forum, but here it goes.

 

I was riding home from home last week splitting lanes on the famously congested 10 freeway here in Los Angeles. About 10 miles down my route home it felt line my bike was losing torque. Riding another 10 feet I realize it felt like the brakes were being applied so I started moving off the freeway from the far left lane. One lane over my front tire slips from under me and I go down on the freeway. Luckily the usual LA traffic probably saved my life because everyone was only moving 15 mph. A UPS truck stopped in time 5 feet from my on the ground. I pick up the bike to start it and I realize the front brake was locked. Being stupid I reached down by the calipers and immediately burn my fingers on the blistering hot brake disc. The front brake lever is in fact not pulled back in the braking position, but extended fully forward and with all my force I cannot get the lever pulled back at all. Long story short, even 15 minutes later standing there on the freeway now being protected by a cop's car and waiting for a tow(the bike needs to be lifted up), the bike won't roll. Five minutes later out of habit I check if the bike can roll and sure enough it does and the front brake lever is functional. 

 

WTF happened folks?  I am afraid to ride the bike now. If I had been doing 70mph and the front brake locked I would be dead. What could cause this? What should I look for? Thanks.

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Glad you're OK. It's rare that we have a cause to celebrate the slow-moving traffic in LA.

 

Have you been messing with the adjuster screw on the brake lever - the one that pushes into the master cylinder? If you've removed too much freeplay by turning the screw in, it can stop fluid from returning. I did this on my clutch and had exactly the same symptoms at the lever - but the clutch just slips when that happens so it is only annoying, not dangerous like the brakes.

 

At a minimum, you should flush the front brake system. It might be time to rebuild the calipers or master cylinder too. Sometimes a brake line can deteriorate on the inside. You might also check if the rotors are warped. If you want to be super-sure, you can rebuild or replace everything in the front brake system pretty affordably (most expensive is new rotors if needed).

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Were both rotors/calipers hot ? Has anyone been adjusting the master cylinder stop screw ? If so you will have to back it out until it does NOT touch the piston ., This keeps it from being a hydraulic jack . If this is ok go to the next step .

 You will have to get the front wheel off the ground and spin the front wheel and apply the front brake . The front wheel should stop and when you release the brake lever it will be free to roll. 

 If the wheel does not spin break one caliper bleed screw loose and see if it spins .If not try the other side . This test will prove whether or not the problem is in the caliper(s) or not . If they do not release , it is the caliper(s). Remove them one at a time to see which one is sticking.

 If they are not at fault , the next step is the brake hose or master cylinder. Pull the front brake lever 3 Xs and release . If the brakes hold , loosen the bolt holding the banjo fitting to the master cylinder . If the brakes release , the problem is "probably" the brake hose .

Don't forget brake fluid & painted surfaces do not mix .

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Thanks guys. Ugh. I did recently put on aftermarket brake and clutch levers. I didn't even think about the adjuster screws. I have backed out the adjuster now a bit on both the brake and clutch. But sorry, still don't think I understand why having the "piston" partially in would cause the problem I had. And why would the lever have been forced open not even allowing me to squeeze the clutch ?

 

I did not check if both rotors/calipers were hot. I'm going to spin the front wheel tomorrow, but how do I check for warped rotors?  Visually I should just be able to see this by spinning the front wheel?

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If the piston is pushed in enough to cover the fluid return hole, it creates a sealed system from the master cylinder down to the calipers. As the fluid heats and expands, it has nowhere to go and starts applying the brake, which creates lots more heat. You know what happens next. The fluid needs to escape through the small return hole in the MC as it expands.

 

Pulling on your brake lever, you were trying to compress a column of already high-pressure brake fluid.

 

You really need a dial indicator to check the rotors, but if you ride the bike and don't feel any brake pulsing, you should be ok.

 

I would also pull each caliper, one at a time and verify that you can push the pistons back, so you know the problem is fixed and won't repeat itself.

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If you still have your take-off levers, you can compare where the screws were set.

 

For the calipers, you can cut a block of wood so you can work one piston at a time. You do not need to remove the calipers (as in my picture). Instead, you can use the brake lever to push out one piston at a time for cleaning. If you are not rebuilding the calipers, don't push the pistons all the way out.

 

IMG_6982.jpg

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Did this happen AFTER you installed the levers ? What brand did you buy & adjust the screws ?

He said..

 

 

I did recently put on aftermarket brake and clutch levers. I didn't even think about the adjuster screws. 

:)

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Thanks guys. What should I be using to clean the pistons? And this did happen after I installed the levers. I got the levers off of Ebay. No brand that I can see.

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What I do is push 1 piston out at a time, just past where they normally extend. I use a small brass bristle brush to clean off the junk, and use a 90 degree snap ring plier inside the pistons to turn them so they can be cleaned all the way around. Be careful not to let the pistons come out too far.


 


18_4_snap_ring_pliers_04.jpg


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Thanks guys. What should I be using to clean the pistons? And this did happen after I installed the levers. I got the levers off of Ebay. No brand that I can see.

 

Link to ebay page and pictures of your levers, please.

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