SF3 rear brake bleeding

M

macavity99

Full member
Location
Bedfordshire, UK
Just replaced rear brake caliper pistons / seals and rebuilt the master cylinder. All reassembled, although new brake pads a very tight fit.

Have read the brake bleeding thread but decided to bleed in traditional way as I have one of those one-way bleed tube kits. After much pumping finally managed to get some pressure on one bleed valve. Started other bleed valve and lost all pressure again. Now can't get any pressure on either valve.

Anyone have any tips to get my rear brake bled and working?

Thanks, Steve in UK
 
Apply some draw at the nipple whilst you bleed normally. ditch the valved bleeder. Buy the biggest syringe your local chemist has, and suck as you pump. You need 3 hands or a buddy.

Hth. Paul
 
I found it less frustrating to remove the entire rear brake hydraulics off the bike, rig it up in a makeshift jig of sorts and bleed it on the bench with the caliper nipple uppermost otherwise I just seemed to be pushing a bubble of air backwards and forwards in the raised 'arch' of the hose, and then refit as an assembly.
 
Owdbiker said:
I found it less frustrating to remove the entire rear brake hydraulics off the bike, rig it up in a makeshift jig of sorts and bleed it on the bench with the caliper nipple uppermost otherwise I just seemed to be pushing a bubble of air backwards and forwards in the raised 'arch' of the hose, and then refit as an assembly.
Click to expand...

Even easier when rigged up so the M/C is uppermost, can leave any bleed nipples shut.  Need to make sure any trapped air can travel upwards from the caliper, just little movements of the M/C lever has bubbles escaping into the reservoir.  Jiggle the lever until no more bubbles appear, fill it up, re-fit and Robert's your mothers' brother... entire process normally doesn't take longer than 20 minutes.

piet
 
I usually use a vacuum bleeder too, driven by a 10bar/140psi air line, should create more than enough vacuum.  But it doesn't always work, depending on hose cross-section and the bends involved I guess.  Now and then, I need to resort to manually bleeding with the system off the bike when starting with an empty system, ie, after a strip and rebuild.  The vacuum bleeder is great for renewing the fluid in an already air-free system, but cannot guarantee that all air is excluded when working from an empty system.  Often end up with a mushy feel at the clutch, so the M/C is removed and held thus that my described method works.  Only takes a couple of minutes.

piet
 
From time to time I have difficulty with a completely empty new system. Other times it goes smoothly.
I use a large syringe on the bleed nipples to get the flow started and then return to conventional bleeding once it has fluid in the system.
Ironically I find more problems bleeding the front than the rear.
 
I like the sound of piet's method:

Even easier when rigged up so the M/C is uppermost, can leave any bleed nipples shut.  Need to make sure any trapped air can travel upwards from the caliper, just little movements of the M/C lever has bubbles escaping into the reservoir.  Jiggle the lever until no more bubbles appear, fill it up, re-fit and Robert's your mothers' brother... entire process normally doesn't take longer than 20 minutes.
Click to expand...

Doesn't the strange angle of the m/c piston have any effect -- the m/c to hose union is at the top of the m/c. So how does the trapped air travel down to the ports below the reservoir? Or does the m/c have to be oriented in a particular way?

Thanks

Steve
 
Just have to hold the M/C so the hose union is lower than the feed bore in the bottom of the reservoir.  Does help if the hose does not exit at a wierd angle.

piet
 
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