Motorcycle brakes locked up today, need some advice?

Question

Today after I stopped for gas on my Suzuki Bandit 600, the front brakes locked up. After driving home with this condition the calipers were smoking, only way I could get the motorcycle home. I need some advice on what would cause this problem and what to look out for? I also took off the calipers and the cylinders seemed to compress without difficulty. I also inspected the master cylinder and it seemed to be pumping fine. One thing I noticed was that the left front rotor seemed to be slightly warped, but that could be due to the brakes being locked and me riding it home. Also I have never had any prior brake problems and they were working correctly the day before.

Answer 1

First off only the brake pads and rotor have friction, so the brake pads smoked and not the calipers. The cylinders had to get stuck. The brake fluid can't apply pressure by itself. You applied pressure, the cylinders squeezed the pads around the rotor, you released your pressure and the cylinders hung up and stuck there....end of story - case closed....

If the calipers were smoking then the pads got so hot that they fried the fluid in the cylinders and now you have gunked up brake lines and cylinders. That wouldn't have created the actual lock up though unless your cylinders have been squeezing the pads for miles and miles and you have been burning up the system for quite some time until it finally locked up like you reported....

It's a straight forward mechanical system that relies on hydraulic pressure applied by your hand, nothing else contributes.

Answer 2

check to make sure your hydraulic hoses aren't kinked when it turns all the way to the left or the right.... after i took my bike apart and put it back together i had the brake line wrapped wrong and at full right turn, the brakes would lock up.

other things to try are changing the fluid and bleeding them, checking to make sure your disc isn't bent or crooked....

and yeah you are lucky to of gotten it home... one false move and you would have been flung over the handle bars and had a dentist appointment with the pavement.

Answer 3

You say you removed the calipers and the pistons compressed easily.  That means the pistons aren't stuck, normally caused when moisture in the system corrodes the cylinder.

That leaves the lines and master cylinder.  Old brakes lines sometimes swell internally and won't let the fluid return to the master cylinder, keeping them applied.  If your bike has dual discs up front, were both of them hot?  If so, that rules out the two lower brake lines because the probability of two lines both failing at the same time is astronomical.  However, it could be the line from the junction to the master cylinder that's failed or either if your bike has a single front brake.  A swelled line will usually relieve the pressure if allowed to set over night.  You leave ok but as soon as you apply the brakes real hard, it locks up.    

The master cylinder could be bad, but I don't really suspect that.  The little return hole could be plugged, but with fluid pushing out the hole, it would be hard for a piece of crud to stay lodged in there.  Bad seals on the master cylinder usually fails to pressure up the system, not depressure it.

If the system were together, you could apply the brakes hard to stick them and thenstart loosening the banjo bolts at the different connections.  For example with the brakes stuck, if loosening the bolt at the master cylinder makes no difference, then that rules it out.  If you loosen the bolt where the single like connects to the junction block and the brakes still stick, then you go to the lower lines.  If you loosed the bolt at the caliper and fluid squirts out and the brake releases, you know it's that lower line.  If the brake stays locked, then it's the piston stuck in the cylinder.

  

Answer 4

I wouldn't ride that thing right now. That could be bad. You could low side. Everything can't be working. Something went wrong. Did you top up the brake master cylinder recently? Did you use the wrong brake fluid by accident? Was the cap loose? The vent blocked? You don't want a warped rotor either. How many miles on this thing?  

Answer 5

There is a small "return" hole in the master cyl.  When you release the brake lever, the fluid gets back into the reservoir through it allowing the pads to release.  If it becomes clogged then your pads can't release.

Answer 6

crud around the brake piston stops it releasing freely ,

Answer 7

maybe it needs some cleaning. try to bleed it also, or better yet change the fluid.