Knackered my rear brakes

[arizonabay]

...I know there are loads of posts regarding Falco rear break issues and I have read most of them. My problem does not seem to be covered. Here’s the issue:

A few days ago I adjusted the push rod on the rear master cylinder to raise the grab point. I went for a ride only to find the pads had bound on the disc and when I stopped it was too late...the rear disc was fecking hot and brake lever was no longer clamping on the disc. There was nothing, no sign of any movement from the pads and no resistance through the lever

So, after some trouble shooting I figured I had cooked something in the caliper and bought a second hand one from eBay. Fitted it tonight following KZMILLE's instruction and still nothing. The brake lever just bottoms out applying no pressure to the pistons.

When I depress the leaver, fluid is travelling through and out the bleed nipple but just does not clamp on the pads????? I have fed about 6 reservoirs of fluid through and still nothing, when you press down the lever there is no resistance at all.

I have manually primed the master cylinder (again as per KZMILLE) so that seems fine.

I did however notice a small amount of fluid inside the braided hose on the caliper end, not sure if that is significant but I am now stumped.

I appreciate any help here.

[Falcopops]

Changing the length of the link rod shouldn't have caused the brake to bind on, so that needs to be resolved too. You may have inadvertantly had your foot on the lever, need to check or it'll happen again.

Bleeding the back brake is a pain and KZ's method is pretty foolproof.

Did you push the pistons all the way back in?

Have you tried reverse bleeding?

I will bleed for a bit, then fill the res and punp the lever with the bleed nipple closed to try and get some pressure into the system, then quickly crack the bleed nipple open and closed, then repeat until I start to get movement in the pistons. Once the pistons are out (put something about the same thickness as the disk between them) then bleed the KZ way to get all the air out and all should be well.

I'm not sure what you mean by seeing fluid inside the braided hose, but if you mean under the plastic tube then I'd suspect the hose has been cooked too. However, I'd expect there to be lost of it once you get some pressure in there, so keep watch on it.

Good luck.

[D-Rider]

Changing the length of the link rod shouldn't have caused the brake to bind on, so that needs to be resolved too. You may have inadvertantly had your foot on the lever, need to check or it'll happen again.

Hmmmm .... I think there is a possibility you can do this.
I've not double checked how far you can adjust the rod but I do know that the rear brake pedal on mine is not high enough for me (or it wasn't until it got bent a bit). The problem is it can't go any higher because of the "stop" on it.
If you were to try winding the link rod out to raise the pedal, the pedal won't move further because of the stop - but you'll start pressurising the rear brake (assuming it adjusts far enough ... which I guess it may do). This could basically apply the rear brake.


As for solving the problem about bleeding it, without actually seeing it, nothing really comes to mind other than what has already been discussed (but if I think of anything, I'll say so).
Of course, when all other ideas fail, the man from Tamworth is usually a good source of help - give Griff a ring.

[arizonabay]

...it must have been the push rod 'cos the chances of me accidently applying the rear break are nil. I noticed it when I coasted to a set of lights and consciously checked if any breaks were being applied.

Without knowing too much about breaks, is it possible to have that much fluid flowing through the bleed nipple without closure of the pads? Does trapped air have that much of an effect?

Now, how do I get hold of this Griff fella? Would you mind pm'ing his number or how to get hold of him.

[D-Rider]

Without knowing too much about breaks, is it possible to have that much fluid flowing through the bleed nipple without closure of the pads? Does trapped air have that much of an effect?

Yes and Yes

If you have a pocket of air that the fluid can get round then it will come out without shifting the air .... and, yes, air is very compressible and it will give that effect

Now, how do I get hold of this Griff fella? Would you mind pm'ing his number or how to get hold of him.

http://www.apriliaperformance.co.uk/

[arizonabay]

Thanks D-Rider - top advice and help again.

[Nooj]

At a guess I'd say the master cylinder seal is fucked. We've got through a number of these last year trying to get our rear calipers working properly. As well as the poorly positioned caliper, I think crappy m/c seals are a major part of the non-working Aprilia rear brake problem.