Help me with brakes please!
Posted: Mon Aug 13, 2007 8:24 am
Hiya! I gave my girlfriend a ZXR 400 to race with and we've now after a year encountered a brake issue. There is no pressure in the system anymore. And the brake lever is extremely soft and touched the handlebar.
What I've done:
I've changed ALL seals in both the calipers and also the pump have had everything inside changed, but there was zero difference and it actually sort of got worse. So I bought new brake pads, even though the current pads wasn't even half used. It didn't help either. I tried bleeding more (hours), and it's a little bit better. I've tried to follow the lines and find the airbubbles and squeeze them out. I've successfully removed a lot of air. I also use a vaccum based pump to suck fluid through the system, and gone through about 0.5 liters of brake fluid (Motul RBF600). There just cannot be anymore air in there.
What I've not done:
The only thing I have not changed, are the pistons in the calipers. But I figure, since they don't leek, they do their job. Am I correct? They are also way too expensive. They are 1/10th of the bike's value at a sale.
In action:
The brakes fade the warmer they get, and eventually... while riding the bike, the brake lever is touching the handlebar on hard braking.
Note 1:
Watching the pistons move as I press the brake lever, they travel very far, maybe 1(maybe more) mm before touching the brake discs. Upon releasing the brake lever, they travel back the same 1-2 mm distance. I am thinking, shouldn't the pads be much closer and almost touching the discs when the brake lever is not used? This is the way on my race bike (riding an aprilia rsv1000r factory bike). The front wheel on the ZXR can spin without stopping for atleast 10 cycles. On my race bike, I can hardly get 1 cycle when spinning the front wheel.
Note 2:
Something I've noticed is that if I squeeze in a wrench between the brake pads on both sides, where the wrench is almost 1 cm thick, the brake system get FULL and VERY good feel in the brake lever. The lever about stops in just 1-2 cm.
What I've done:
I've changed ALL seals in both the calipers and also the pump have had everything inside changed, but there was zero difference and it actually sort of got worse. So I bought new brake pads, even though the current pads wasn't even half used. It didn't help either. I tried bleeding more (hours), and it's a little bit better. I've tried to follow the lines and find the airbubbles and squeeze them out. I've successfully removed a lot of air. I also use a vaccum based pump to suck fluid through the system, and gone through about 0.5 liters of brake fluid (Motul RBF600). There just cannot be anymore air in there.
What I've not done:
The only thing I have not changed, are the pistons in the calipers. But I figure, since they don't leek, they do their job. Am I correct? They are also way too expensive. They are 1/10th of the bike's value at a sale.
In action:
The brakes fade the warmer they get, and eventually... while riding the bike, the brake lever is touching the handlebar on hard braking.
Note 1:
Watching the pistons move as I press the brake lever, they travel very far, maybe 1(maybe more) mm before touching the brake discs. Upon releasing the brake lever, they travel back the same 1-2 mm distance. I am thinking, shouldn't the pads be much closer and almost touching the discs when the brake lever is not used? This is the way on my race bike (riding an aprilia rsv1000r factory bike). The front wheel on the ZXR can spin without stopping for atleast 10 cycles. On my race bike, I can hardly get 1 cycle when spinning the front wheel.
Note 2:
Something I've noticed is that if I squeeze in a wrench between the brake pads on both sides, where the wrench is almost 1 cm thick, the brake system get FULL and VERY good feel in the brake lever. The lever about stops in just 1-2 cm.