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Bleeding rear brake - or not.


szurszewski

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szurszewski

I ran into a bit of trouble with my rear brake earlier. To start, this is a 96 R1100RT, and as of yesterday the rear brake worked normally (which is to say, it worked like it usually does...not much). Today, as part of adding a sidecar, I plumbed in a second brake line - the setup basically replaces the banjo bolt at the rear caliper with a doodad has a two hole banjo bolt, and the second line comes off from there to the caliper on the sidecar's brake.

 

I hooked up the new line to the sidecar first, then hooked it up to the RT. When I opened the rear brake reservoir, I found it all but empty - I assume, since the brake functioned yesterday, fluid was moving from the reservoir into the new parts of the system. I added fluid, put a one man brake bleeder on the sidecar's bleed valve and cracked the valve. I pumped some fluid out of the reservoir as expected, refilled it and then tried again...only, now pumping the brake doesn't seem to have any effect on the fluid in the reservoir.

 

I know there are now several potential points for leaks, and when I get home from work - or probably tomorrow - I'm going to disconnect sidecar parts and return the system to original form and see if at least I can get that to bleed properly. If so, I'll look for leaks in the sidecar side of things.

 

If I get it back to original form and still can't get the pedal to pump fluid out of the reservoir, what's the next thing I should try? The rear brake line - I'd have to check my records to be sure - was replaced by me sometime after 2008, and likely after 2010. I've had no problems since replacing that line (and no problems before actually - just noticed the hose was starting to buldge one day).

 

Any suggestions appreciated. Also, if you have any tips on how to assemble brake lines and fittings, that would be appreciate too. I can probably google that up, and I'm hoping/assuming that's where my problem is coming from (the brake parts came as a kit with a legth of steel braided line and the banjo fittings).

 

Thanks!

josh

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Morning Josh

 

First thing-- did you remove the rubber baffle cup in the rear master cylinder resiviour? If that rubber baffle is still in the resiviour then the fluid will sit on top of that & not get to the caliper. My money is on this one.

 

Otherwise, going back to stock & just one rear caliper is probably a good place to start over.

 

Could be a delaminated rear brake hose but that is doubtful if it was working before.

 

Is that new rear banjo fitting open & the holes lining up with the brake hoses?

 

Is the rear master cylinder piston FULLY returning, if not it might be blocking the internal fluid hole.

 

 

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szurszewski
Morning Josh

 

First thing-- did you remove the rubber baffle cup in the rear master cylinder resiviour? If that rubber baffle is still in the resiviour then the fluid will sit on top of that & not get to the caliper. My money is on this one.

 

 

 

 

 

I'd put money on your money.

 

My wife got called in to work at 4:30 this morning - I gave up on going back to sleep and spent the better part of an hour returning this system to original and then trying again. Same results. Gave up, closed up the garage and started getting ready for work - ten minutes into my shower I woke up and thought, golly, I forgot to take out the baffle!

 

(Ok, actually I thought something with more words, most of which I wouldn't post in this forum.)

 

I just logged in now to update this thread with that info - but of course, you beat me to it. I've got a long lunch break today - probably stop by the house and try to bleed again sans baffle - hopefully that will be it.

 

Thanks much for taking the time to point out my foible!

josh

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Afternoon Josh

 

If you indeed did bleed all the brake fluid out from under that baffle then there is a good chance that you NOW have some air trapped in the ABS controller & might have to bleed that at it's bleed fitting.

 

My other concern is you have your side car wheel brake plumbed into the rear brake ABS controlled circuit (assuming you still have ABS brakes). That side car brake has no wheel sensor of it's own so it won't take much of a slip on the motorcycle rear wheel during braking to lose (or degrade) ALL rear braking. Your ABS rear circuit definitely isn't set up to modulate two rear caliper volumes.

 

 

 

 

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szurszewski

I share both those concerns - or at least both those thoughts; I wouldn't say I'm concerned about the potential rear brake issues but I am curious to see what the ABS controller does with that additional wheel. Planning to post some questions potentially about that once I get it things put back together and working.

 

Thanks again!

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szurszewski

Update:

I have managed to bleed fluid through both calipers and the abs controller up under the tank. Pressing the pedal moves fluid and will activate the calipers, but the pedal is very soft, goes easily to the stop, and take a couple pumps to feel any braking when riding (and even then it is only marginally effective).

 

Do I need to look into the master cylinder? If so, any tips before I just start taking things apart?

 

Thanks!

josh

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Morning Josh

 

It sounds like you still have some air trapped in the rear system (air likes to stay trapped in the high spots as the fluid passes under it).

 

Once you are SURE you have all the air out of rear lines, hoses, calipers, ABS controller, & master cylinder THEN you can evaluate (IF) you have enough rear master cyl volume to operate both the old caliper & new added caliper.

 

Depending on how much brake-pad/caliper-piston kickback you have I would imagine your pedal will have to travel farther to get the same rear braking pressure.

 

Hopefully what you initially lose in pedal travel vs rear braking pressure you gain most of that back with two rear brakes requiring less brake pedal pressure to stop the vehicle.

 

My guess is that you should be able to get decent NON ABS rear braking as long as you don't have a lot of pad kick back.

 

I'm not sure if the ABS system has enough capacity to reestablish full rear braking once the ABS system goes into ABS though (you will have to feel that one out as you ride the bike)

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szurszewski

Good Morning D.R. -

 

Ok - I'll go through and check everything thoroughly to make sure it's all set up properly and then do a careful bleeding. I'll reread some tech articles on that to see if there's any tricks I'm missing, but if you have any tips I'd take them.

 

I initially tried using my mightyvac but switched back to old school turn pump the pedal, open/close the bleeder, release the pedal for the latest round. Doing this I have it now where I do not see any bubbles anywhere - in fact, I saw new fluid right away when I opened the bleeder on the ABS controller.

 

If I'm doing all the bleeders in the system, I assume it's best to start at the ABS controller since it's on top, yes? I've seen a few tech articles on this particular system and they have conflicting opinions on that (including whether or not there's any reason to bleed from the controller at all - I assume there must be since there's a bleeder on it...).

 

As always, thanks!

josh

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RoanokeRider

I have a friend with a 2000 R1100R with a Hannigan sidecar, no ABS. He was not able to get the set up working with the rear brake plumbed to the sidecar brake. Jay at DMC told him the the BMW rear caliber did not have enough fluid to operate 2 calibers and the the rear/sidecar brake would be weak. The solution was to use a second master cylinder for the sidecar brake and link it to the rear brake pedal with adjustable linkage. Works for him, YMMV.

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szurszewski

Thanks for the info, Bill. I have been futtzing with it the last hour with some improvement, but not much. While I was in there I did pop in some new brake pads, so at least that was worthwhile.

 

While futtzing I was considering how complex it would be to do just that - if you could pm me contact info for your friend, or I can give you mine to give him, I'd like to get in touch.

 

josh

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RoanokeRider

Josh, I just spoke with him earlier today. He stated that one of the ways to tell is to use the quick disconnect to disconnect the sidecar and try the brakes then. If the brakes work, the problem is the fluid volume. Bill Draper can be reached at draperg1@comcast.net

 

He is a great guy and is becoming quite knowledgeable about sidecar rigs. Mine has been in his shop for 3 weeks now while we get it set up. We have had to make and/or modify a lot of pieces.

 

Good luck with yours.

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szurszewski

Hi Bill -

I don't have a quick disconnect in the brake line, but my next step is going to be to "slow" disconnect the sidecar part of the circuit to see if I have regular braking restored. If I do, then I'll work on making the sidecar circuit separate.

 

Hacks do seem to be fiddly - I bought the sidecar itself last summer, spent the next few months slowly acquiring what I thought were all the parts I needed, and then started trying to put the rig together in maybe late November... still working on putting it together :) Had to replace some parts, have a bit of welding done, get some parts I didn't know I needed, and now that I have the bike and car physically together I'm embroiled in the fun of making it all work!

 

Once I see if I can make the rear brake work solo again, I'll drop the other Bill an email.

 

josh

 

 

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RoanokeRider

Josh,

I guess it is just the nature of sidecars. I made the subframe for my airhead and it did not seem to be any more difficult and time consuming then using the store bought one for the oilhead. And it seems that you are never done. I know that after he rode is R1100R some, Bill went to an R850 final drive. I may also once I have ridden mine some. Then there is converting to a car pusher tire for the bike, and then...

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szurszewski

Ok - so continuing with the above, I've concluded that the rear master cylinder just doesn't have the oomph for the extra caliper/brake line on the sidecar. I've got everything, bike-side, back to stock (and with new pads!) and it's back to working well - better than before even (probably the ABS bleed I did along with the new pads).

 

I'd still like to have a sidecar brake, so I'm planning to add an additional master cylinder for that circuit and have it activated by linkage from the rear brake pedal (along with the bike's rear brake of course).

 

Eddd happens to have the rear brake master and reservoir for sale; I'd like to use that so I'll have some duplicate parts in case one fails on the road or whatever. Here's the question:

 

Is there any reason the master from an R1100RT WON'T work with the port for the ABS controller blocked off?

 

My plan would be to have the circuit just be master cylinder, reservoir and the brake line and sidecar caliper.

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