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Discussion Starter · #1 ·
I was checking the shop manual for the 2021 model and noted that bleeding the rear caliper is to be done with the caliper on the bike. I found this interesting as I have watched videos of bleeding the rear brakes on bikes with the underslung calipers and many of them recommend removing the caliper in order to place the bleed nipple in a more elevated position.

What are some thoughts on this? If there is air anywhere in the system from the caliper to the reservoir, wouldn't that air migrate to the highest point which is the reservoir? I have a stop light switch on order for the Bonamici rear set and was hoping to simplify the job as much as possible as it appears the stop light switch plug requires tank removal and not having to do mechanical gymnastics with the rear caliper would be a welcome reduction in labor.
 

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Both the banjo attachment and bleed bolt are below the highest point of the pistons. You will never be able to bleed all the air out if you leave the caliper on the bike.

It's only 2 bolts to take the caliper off, so it's best to do it properly with the banjo at the highest point.
 

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What do y’all recommend as far as keeping the calipers apart. Either let them move all the way together, or wedge something between them to maintain space?
 

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I added the underslung caliper to another motorcycle and found it to be exactly as 09 Blade said it would be with a emphasis on never.

The caliper was brand new so it had more air than a normal bleed or fluid change.

I wasn't paying attention to how much fluid I was using. Within a few minutes, the new bottle was empty and the brake was still full of air. I ended up using my air powered bleeder. That was much more successful and my brake was ok within a few pulls of it's magic lever. The normal was would move fluid right around the trapped air.

The next time I removed the caliper and used a wooden paint mixing stick to keep the pads apart. It's thickness was almost identical to the caliper.....4.5 or 5mm...whatever it happened to be.
 

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Discussion Starter · #5 ·
Thank you for the replies, I'll have to figure out a third hand somehow...

I've got the rear wired in-line pressure switch for the Bonamici set and would rather not remove the tank to plug that thing in, would a simple splice into the existing switch wires work? I've confirmed the switch is still hooked up as I got a light when pulling the activator on it.
 

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Were you not planning to remove the stock switch from the bike? It's 2 wires and if you are planning a permanent install just cut them and splice the two wires directly to the pressure switch. You have several inches of extra wire because the pressure switch mounts higher than the stock switch.
 

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Discussion Starter · #7 ·
Were you not planning to remove the stock switch from the bike? It's 2 wires and if you are planning a permanent install just cut them and splice the two wires directly to the pressure switch. You have several inches of extra wire because the pressure switch mounts higher than the stock switch.
I wasn't planning anything--I bought the bike used, and, unfortunately, the previous owner did not have the OEM rear sets so I'm left with this. The dealer neglected to inform me that there was no rear light functioning so I found out after the first ride of the bike after delivery. Not a great place to find out you don't have rear bake lights. I looked into buying the OEM rear sets but that's a bunch of money I don't want to spend. Fortunately they did have the OEM exhaust they took off for the slip-on but that's another project for another day.

Anyway, I'll splice up the wires and call it good.
 

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So, on the rear calipers, there are two designs used in the under slung brake. The best one to use has the bleed nipple at the top of the caliper when mounted and can be bleed in place. The second caliper used in the under slung position was really meant for above the axle mounting so the bleed nipple would be at the top but in under slung mounting the bleed nipple is at the bottom, to get a good bleed it is necessary to remove and have the nipple up, put something between the pads, then bleed it.
 

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Discussion Starter · #10 ·
So, on the rear calipers, there are two designs used in the under slung brake. The best one to use has the bleed nipple at the top of the caliper when mounted and can be bleed in place. The second caliper used in the under slung position was really meant for above the axle mounting so the bleed nipple would be at the top but in under slung mounting the bleed nipple is at the bottom, to get a good bleed it is necessary to remove and have the nipple up, put something between the pads, then bleed it.
I've got a paint stirrer stick that should work perfectly for keeping the pads apart. Are there alternative calipers that have the bleed nipple at the top that would be a direct bolt on? I suppose it wouldn't be too difficult to fabricate a simple stand that the caliper could be bolted to with the bleed at the top.
 

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I bled my 2011 using just the bleed valve, a hand pump & no more than 20 millibars. Rock solid now.
2011 OEM caliper is single piston top mount with bleed valve at highest point so it's quick to bleed without having to flip it over.
 

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Toy Wheel Gas Auto part Machine

The rear caliper on my Concours 14 has two bleed nipples. It's underslung in it's original form. I have always been able to bleed it without removal, but you have to use both bleeders for the best performance.

Performance? It sucks because the master cylinder ratio isn't correct for the caliper size, like most Japanese bikes, but it is well bled.
 

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Both the banjo attachment and bleed bolt are below the highest point of the pistons. You will never be able to bleed all the air out if you leave the caliper on the bike.

It's only 2 bolts to take the caliper off, so it's best to do it properly with the banjo at the highest point.
I tried fo 2 days until I did what this post said
 
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