Rear brake binding

  • Thread starter Thread starter Webgrecian
  • Start date Start date

Webgrecian

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I am having problems with the rear brake on my 1100GS. After riding for a few miles it locks on. I changed the rear caliper (the pistons wouldn't retract once the system was drained and so I assumed the pistons were knackered), but after taking the bike out for 40 odd miles with the new caliper the same thing happened.

The disc has been checked and it isn't warped.

I'm wondering if this is an ABS issue. When I stop the bike and rock the caliper back and forth it is clear that the brakes have some movement. When I start the bike up afterwards it then runs freely for a few more miles before it locks up again.

Any suggestions?
 
Are you sure you aren't accidentally applying the brake (foot position).
Are the pads correct for the bike and do they move freely in the caliper (not seized on guide pin).
 
I had the same problem with my 650 and it was the master cylinder I think they use the same Brembo unit. The cheapest I could find was from intobikes excellent service too. I don't know if there is any difference but I don't have abs on my bike.
 
Is anything obstructing the brake pedal from retuning fully after being pushed, is the lever partly seized? Is the master cylinder piston seizing up?

When was the calliper last cleaned up? Maybe the calliper pistons need a good clean, crud around the pistons can tend to hold the brake on.
 
No to all the above, the piston is not seized because when I stop the brake moves freely when moved 'physically' back and forwards on the disc. I am sure I'm not applying my foot to the brake and I'm also sure the brake pedal isn't seized. The bike runs freely for a few miles after I start the bike again before binding once again.

The replacement caliper was checked before it was put on the bike (after the same problem with my old caliper) and so that is highly unlikely to have seized in on day's use.
 
Webgrecian said:
No to all the above, the piston is not seized because when I stop the brake moves freely when moved 'physically' back and forwards on the disc. I am sure I'm not applying my foot to the brake and I'm also sure the brake pedal isn't seized. The bike runs freely for a few miles after I start the bike again before binding once again.

The replacement caliper was checked before it was put on the bike (after the same problem with my old caliper) and so that is highly unlikely to have seized in on day's use.
Click to expand...
Does the wheel lock up when the brake goes on?
 
No, it doesn't lock but the brake is obviously on hard as all accelleration goes, the rear wheel weaves if I apply too much throttle and you can smell the pad burning if you don't stop pretty sharpish.
 
its a lack of free play in your rear brake pedal - blocking the return circuit in the master cylinder.

loosen it right off
 
This doesn't happen every time I apply the brakes though so do you still think its a lack of free play?
 
motomartin said:
its a lack of free play in your rear brake pedal - blocking the return circuit in the master cylinder.

loosen it right off
Click to expand...

mine was the same, bought new master cylinder, the problem was same..
so i backed off the rear brake, and it gave the calliper more free play to move the pistons...

worth a try for nowt....:augie
ugg
 
Webgrecian said:
This doesn't happen every time I apply the brakes though so do you still think its a lack of free play?
Click to expand...

Guarenteed. ( almost :))

you're probably at the small limit of free play - and also have a bit of air in the system.

As it all heats up, the air expands, closing your free play down even more - the return cct closes and bingo - the piston can't return
 
Ok this is getting really annoying now. This has mystified me so I took the bike into a specialist this morning (unfortunately the brake seized up without me even applying it while driving on a short stretch of 3 lane fast bypass - which I couldn't avoid - on the way, talk about a near death experience!).

He has checked and:

  • the disc isn't warped
  • free play is fine
  • the pads move freely on the sliders
  • the pistons are fine
  • there is no ABS fault
  • fluid level is fine

In other words he can find nothing wrong. He has, however, changed the rear master cylinder in case that is causing the problem. He's going to give it a 10 -15 mile run tomorrow morning and see if it seems okay.

Let's sodding hope so, I'm at a loss. :tears
 
Webgrecian said:
Ok this is getting really annoying now. This has mystified me so I took the bike into a specialist this morning (unfortunately the brake seized up without me even applying it while driving on a short stretch of 3 lane fast bypass - which I couldn't avoid - on the way, talk about a near death experience!).

He has checked and:

  • the disc isn't warped
  • free play is fine
  • the pads move freely on the sliders
  • the pistons are fine
  • there is no ABS fault
  • fluid level is fine

In other words he can find nothing wrong. He has, however, changed the rear master cylinder in case that is causing the problem. He's going to give it a 10 -15 mile run tomorrow morning and see if it seems okay.

Let's sodding hope so, I'm at a loss. :tears
Click to expand...

Well, what was the outcome?
 
It seems okay, but I'll post again once I have a few miles under my belt.
 
Watching this one with interest as I was out with a mate the other day following him on his R850r, after 35 miles he lost the back brake when the fluid boiled due to the rear caliper binding.
He wasn't riding with his foot on the brake and as a result the rear pads ( newish ebc's) were toasted and the paint burnt off the metal backing and the rear disc ended up warped.
The bikes only done 19,000 and is immaculate.
Replaced the discs with a new grimeca with new ebc pads and bled the system.
When running the bike on the centre stand in gear with the caliper carrier bolted up but he caliper removed the new disc is true and it runs right in the centre of the carrier BUT as soon as the system is rebuilt it binds and eventually begins to lock up.
Put a known good s/hand caliper on and re-bled the system and lo and behold it is just as bad. ( I stripped the original caliper and all of the seals are perfect as are the pistons.
We are going to replace the original brake line with a goodridge (as it is 8 years old) and if that fails the only thing I can think of is the rear master cylinder.
 
Neil W said:
Watching this one with interest as I was out with a mate the other day following him on his R850r, after 35 miles he lost the back brake when the fluid boiled due to the rear caliper binding.
He wasn't riding with his foot on the brake and as a result the rear pads ( newish ebc's) were toasted and the paint burnt off the metal backing and the rear disc ended up warped.
The bikes only done 19,000 and is immaculate.
Replaced the discs with a new grimeca with new ebc pads and bled the system.
When running the bike on the centre stand in gear with the caliper carrier bolted up but he caliper removed the new disc is true and it runs right in the centre of the carrier BUT as soon as the system is rebuilt it binds and eventually begins to lock up.
Put a known good s/hand caliper on and re-bled the system and lo and behold it is just as bad. ( I stripped the original caliper and all of the seals are perfect as are the pistons.
We are going to replace the original brake line with a goodridge (as it is 8 years old) and if that fails the only thing I can think of is the rear master cylinder.
Click to expand...

Motomatrin's diagnosis below gets my vote - I had the same thing happen on a Suzuki due to a master cylinder.

cheers
Matt

motomartin said:
its a lack of free play in your rear brake pedal - blocking the return circuit in the master cylinder.

loosen it right off
Click to expand...

motomartin said:
Guarenteed. ( almost :))

you're probably at the small limit of free play - and also have a bit of air in the system.

As it all heats up, the air expands, closing your free play down even more - the return cct closes and bingo - the piston can't return
Click to expand...
 
i used to own a 635 BMW - and the forums used to say that the original brake lines used to collapse on the inside - effectively turning the line into a one-way valve.

I've never heard of it on a bike though - a long shot if all else fails.
 
Ditto , I've had it happen on car flexis but never on a bike, that said the lines on the 850 are probably due for renewal so its the cheapest option.
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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