dan williams Posted May 5, 2020 Report Share Posted May 5, 2020 Ask ten Beta owners what the worst maintenance task on a Beta is and eight of ten will say bleeding the rear brake. The other two don’t work on their own bikes. OK maybe that’s an exaggeration but it really is evil. My rear brake has been squeeky and weird since a get off last year that bent the disk. Replacing the disk helped but still not right so I went to replace the pads and the hex head on the pad retaining bolt stripped out. Ugh! Screw it. Replace the caliper though I know it meant the dreaded bleed. Hook up the lines, fill the reservoir and pump, pump, pump.... Too much air to make it work. Syringe back bleed to the master alternating push/pull monitoring level in the reservoir got rid of most of the air. Some resistance to the pedal and some pump- hold-bleed-close cycles got it closer. Now the party trick. Pump-hold-bleed-close cycles with the bleeder on top of the banjo on the master cylinder. Took about ten cycles to chase out the remaining air. Still not quite the pedal of doom so I eyeballed down at the disk while the pads engaged and the disk was moving. Disk brake systems are designed to be self aligning and they are on a car where the disk is strong enough to force the pistons into equalizing but the disk on a trials bike is so thin it will flex and then flex back once the brake is disengaged. This little bit of flex acts like a bent rotor only pushing one piston back and the caliper never sets up properly. The fix was to feel the direction of disk flex when applying the brake and apply gentle pressure to the opposite side of the disk to force the weak side piston to adjust out to where applying the brake doesn’t flex the rotor because it is centered between the pads. Much better. This is my custom bleeder setup. Yes it’s easier to just take the airbox out. 2 Quote Link to comment Share on other sites More sharing options...
mcman56 Posted May 5, 2020 Report Share Posted May 5, 2020 Can you buy that bleeder or do you make it? Quote Link to comment Share on other sites More sharing options...
dan williams Posted May 9, 2020 Author Report Share Posted May 9, 2020 (edited) On 5/5/2020 at 12:24 PM, mcman56 said: Can you buy that bleeder or do you make it? I put that together out of the parts bin but it's easy to make one. The normal bleeder is a vee bottomed screw that sits in an angled seat in the banjo bolt. Since it was threaded at the top of the bolt I figured I could just use a screw of the proper size with a copper sealing washer to seal on top of the bleeder and it should work. Yeah it spills brake fluid when you bleed it but I think that is going to happen no matter what. Plus it's titanium! Bling! A regular steel bleeder bolt won't have the higher part on top so it would probably fit better. It'll take some fettling to make it work but it's not difficult. Pretty sure it's effective since I almost went over the bars hitting the back brake over a log Tuesday. ? Of course you can just burp the bolt that's in it if already. Works just as well and is cheaper. Edited May 9, 2020 by dan williams Quote Link to comment Share on other sites More sharing options...
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