Hi, As I'm riding I lose the free play on my rear brake pedal even without using it until the brake comes on and locks the rear wheel! Within around 5 minutes of the engine being switched off the pressure on the pedal gradually frees itself and the rear brake releases. The bike passed its MOT last week as the bike was stood still for around 20 minutes prior to its Brake test. I had the brake fluid changed in case this was a problem by the garage and they checked for correct travel/free play on the pedal. Any suggestions maybe a ABS issue ???
There isn't enough free play at the pedal, so the piston isn't coming fully back. This is preventing fluid in the line from getting back to the reservoir when the pedal is released.so that the brake doesn't fully release. It will be fine until the brake is used a few times and get worse as the brake heats up potentially locking the wheel. I advise getting it fixed asap
Hi, Thank you for getting back to me but there seems to be plenty of free play on the pedal and rod before I use the bike, This happens even when I never use the rear brake, I've purposely gone out for local rides and not used the rear brake!. I will try adjusting the slave rod but I've owned the bike around 4 four years and touched nothing, it just started happening!..
Well whatever it is the fluid isn't getting back to the reservoir. Perhaps the bleed hole is blocked.
The master cylinder. There is a bleed hole which allows fluid from the reservoir to the brake line and hence to the slave. When the pedal is depressed the fluid is pushed down and a pushes out the pistons in the slave, applying the brake. When the pedal is released the piston should move back uncovering the bleed hole which allows the fluid to return to the reservoir. So either there isn't enough free play so that the piston doesn't fully return, the bleed hole is blocked with gunge, or gunge is preventing the piston from moving freely to the fully returned position. Whatever it is you need to inspect the master cylinder.
I'd strip the caliiper and check that the pistons are returning. Perhaps they're sticking in a position that just enages the pads, so the whole thing warms up and siezes.
Sounds to me that your pistons aren’t returning due to the seals having expanded thus not allowing the pistons to return. Had the same on my lads Aprilia I just removed the seals cleaned them up and replaced. I read a while back that it’s the road salt and such that dissolves in water then it evaporates leaving behind the salt in it’s non soluble state which then squeezes the piston preventing its return. As Keith P suggested I’d strip them to rule them in or out of the problem, ensure you know which way round the seals were when you removed them as you can put them in the wrong way round.
I always use the rear brake once or twice per ride on my 939 Hyper just to keep it 'exercised'. They seem to be a rare occurrence of a reliably-working (though mainly unused) Ducati rear brake!
I haven’t used a rear brake on a road bike in possibly 30 years of riding, plus the underslung are a faff to bled IME.
Hi Guys, Thanks for all the comments, I've just come home from holiday and thought I'd have a quick check of my bike. I removed the rear brake cylinder and cleaned the piston etc, everything seemed clean with no signs of corrosion. The adjusting rod and ball joints were in very good condition. The brake fluid was replaced a few weeks ago by the garage that carried out its MOT. I started the bike on its centre stand, I put it into gear and held the front brake. After around 5 minutes of the engine running the rear brake came on slowly until the rear wheel wouldn't rotate, this was without applying the rear brake!... While the rear brake was still on I removed the rear brake cylinder/ linkage etc giving plenty of slack yet the brake was still on! Can the rear brake caliper be getting pressure other than that from the master cylinder ?? Does the front master cylinder have anything to do with the rear brake?? Can this be a ABS fault?? The ABS warning light goes out as it should. After 5/10 minutes of the engine being switched off the brake releases. Thanks
