Rear brake binding and master cylinder Brembo PS11

[Jez2561]

Just thought I would share my recent experiences when suffering from intermittent overheating rear brake on my 2005 V11 Le Mans with 10000 miles.

All appeared fine at the pedal so I suspected rear calliper which I inspected and cleaned, both pistons fine and moving nicely, test ride and still binding. Removed master cylinder which at first appeared fine but I decided to rebuild so ordered repair kit from motomecca.

When the kit arrived the problem became obvious!

The master cylinder piston was not returning fully due to a build up of alloy corrosion within the body of the master cylinder which was squeezing a nylon sleeve which the piston slides up and down in thereby causing pressure to be applied even when pedal not pressed.

I have now rebuild the master cylinder and problem sorted.

 

Just something to watch out for as this obviously happens over time. If you look inside the bottom of the cylinder where the push rod enters you will see the black coloured piston within the white nylon sleeve held in place by a circlip. The piston should return all the way back to the circlip, level with the bottom of the nylon sleeve. If not you probably have the same problem as me. Repair kit was about £20 including postage so probably worth doing next time you change fluid.

 

Hope this helps someone else!

Jez

[docc]

Haven't looked in there for a while.

 

Ew: nasty. Piston returns ok, but time for a clean up and some silicone lubricant.

 

Thanks for heads-up!

 

[luhbo]

You might check the (electrical) contacts on the other end of the cylinder, too.

 

Hubert

[gstallons]

Uh.... NO petroleum products.

[docc]

Hubert,  Good call on checking the electrical connections. They looked good on my Sport, but sprayed some silicone grease there as well.

 

I remember gstallons being emphatic about not using petroleum around braking systems, so I used Sil-Glyde Brake Lubricant and silicone spray lubricant in the lower boot.

 

Added this procedure to the "Wheels Off Maintenance Checklist!"

[Kiwi_Roy]

If I remember correctly, when you pull on the lever the button pops out and the normally closed contact closes. Let the lever go and it pushes the button against it's spring to open the Normally Closed contact.

 

The rear switch is hydraulically actuated, a normally Open switch that is closed when you apply hydraulic pressure.

 

Us sparky types normally refer to the state of a contact when it's at rest with no mechanical input, manuals don't follow any sort of standard, take whatever they show with a grain of salt.

[sp838]

I replaced my rear mc with a brembo for KTM all in one unit, with a finned reservoir extender and a hydraulic banjo bolt switch. Works great, looks great. One less hose to run, easier to bleed, and frees up a bracket under the seat which is better used for grounding stuff. Rebuild kits are readily available for them too.

[nobleswood]

Pictures ! Or it ain't true !

[swooshdave]

I replaced my rear mc with a brembo for KTM all in one unit, with a finned reservoir extender and a hydraulic banjo bolt switch. Works great, looks great. One less hose to run, easier to bleed, and frees up a bracket under the seat which is better used for grounding stuff. Rebuild kits are readily available for them too.

 

Pictures and part numbers.

[sp838]

I'll post pics when I get home but in the meantime Scud is my witness!

[sp838]

Pretty sure it was one of these: http://ebay.com/itm/262961200271

[stewgnu]

I have just toasted the snit out of my rear disc, which melted the lovely gold anodising and left it crisp-shaped. Hashtag sadface.

The cylinder looked clean enough on disassembly.... got a replacement disc coming tomo but concerned it'll happen again...

Why are these rear brakes so crap? Always thought brembo were highly thought of...

[Chuck]

Here's my considered opinion as to what is happening. Of course, it's just a guess. When I picked up Rosie (Rosso Corsa) from Alabama, the rear rotor was blue and cone shaped. (!!) It sounded like a gun went off when I loosened the last rotor bolt. That sucker had been HOT. A guy that used to ride with the Distinguished Previous Owner said he was always riding the rear brake, because you could see his brake light a lot. The brake line was poorly routed, and burned through.

Had a new brake line made up, bought a new caliper and rotor. I don't remember if I rebuilt the M/S or not, but probably did. Went for a ride around the mile square, and the new rotor was hot. Hmmmm. Let it cool, rode it around the square again being careful not to touch the brake pedal, and it was hot. Hmmmm some more. Decided that maybe if all the air wasn't out of the line it could get hot, expand and push the piston against the rotor. ? 

So, I hung a machinists vise from the brake pedal overnight, and the next day the pedal was hard as a rock.

The rotor never got hot again. Take this for what it's worth..

[sp838]

Definitely a good thing to bleed the caliper with it off the bike. Unhook the line from the little tabs on the swing arm and bring it around to the right side and let it rest below the whole assembly. Push the pads all the way in and then put a wooden shim in there to keep them from closing up during bleeding.

[swooshdave]

Here's my considered opinion as to what is happening. Of course, it's just a guess. When I picked up Rosie (Rosso Corsa) from Alabama, the rear rotor was blue and cone shaped. (!!) It sounded like a gun went off when I loosened the last rotor bolt. That sucker had been HOT. A guy that used to ride with the Distinguished Previous Owner said he was always riding the rear brake, because you could see his brake light a lot. The brake line was poorly routed, and burned through.

Had a new brake line made up, bought a new caliper and rotor. I don't remember if I rebuilt the M/S or not, but probably did. Went for a ride around the mile square, and the new rotor was hot. Hmmmm. Let it cool, rode it around the square again being careful not to touch the brake pedal, and it was hot. Hmmmm some more. Decided that maybe if all the air wasn't out of the line it could get hot, expand and push the piston against the rotor. ? 

So, I hung a machinists vise from the brake pedal overnight, and the next day the pedal was hard as a rock.

The rotor never got hot again. Take this for what it's worth..

 

I've had to clamp front brake levers back over night (sometimes longer) to get the last air out.