Hi Guys, My Majesty 180 rear brake went spongy where the lever would go all the way with no resistance - only right at the end of travel you would feel a bit of braking action. If you pumped the lever quickly there would be a bit of resistance in the last 1-2cm of the lever travel and some braking action - but nothing close to normal. It has a Brembo single piston (one each side) calliper with braided hose fitted. Things I have tried; 1. Checked pad & disc thickness - disc 5.5mm all the way around, pads 4-4.5mm. 2. Checked for any leaks/bulges from the calliper back to master cylinder-nothing. 3. Bled the system multiple times with fresh fluid. 4. Left it overnight with the lever tied to the bar. 5. Reverse bled it from the bleed nipple. Then I removed the calliper to check the piston movement. The outer piston was delayed in its movement - the inner piston moved 4-5mm before it started to move. I manipulated it by wedging the other piston in and then it seemed to move almost instantly & was able to push it back in by hand. I did the same to the other piston. After 5-6 various manipulations - the inner piston seemed stuck as I couldn't push it back in by hand. I decided to strip & check the calliper. The pistons popped out ok, fresh clean fluid inside, no sludge or white stuff, seals look absolutely fine (small top seals had a bit of dirt which cleaned off ok), pistons spotless, calliper insides ok & seal channels had some residue which cleaned up ok. So what next? - strip & check the master cylinder? Thx
I would certainly check the master cylinder, as it's a serious safety issue. A vacuum brake bleeding kit is also a worthwhile investment, as it makes bleeding the brakes on a bike a much simpler operation.
Right I removed the master cylinder piston and it looks ok; The outer seal looks fine and in one area there is a little bit of gunk build up; The inner is fine, no rips or tears and is fine around the od - but on the id there is a smooth horizontal groove which doesn't reach the edge of the od; Could this have a part to play? Does anyone know any suppliers for Brembo brake spares? I've search and searched but can only seem to find calliper seals/rebuild kits but nothing for master cylinders for my model - ones that do individual components would be ideal.
