BMW Brake lines
BMW R1100RS Brake lines
Just a few days ago, I went to a business meeting held at a venue in upper Walmer Estate, just below De Waal Drive. Riding uphill from lower Woodstock with my BMW R1100RS was a breeze. After the meeting I left, but as I was riding, something very peculiar happened. Going downhill, I applied the front brake but it felt like the bike was held back a lot more, in relation to the amount of break pressure I applied. When I approached the stop sign I came to a complete stop, however when I pulled away from a standing-still position the feeling of drag perpetuated and the bike behaved somewhat sluggish.
Seeing I was riding down a steep decline, I engaged my clutch to attain free-run. The bike progressively slowed down and eventually came to a halt on the downhill. I then realized that either the front or the rear brakes was binding, alternatively that the front or rear axel was seizing or was at least starting to seize. I then rode the R1100RS a short distance into a side street so that I could check what the problem was. I turned off the ignition and pulled the R1100RS onto the main-stand, to get both wheels off the ground. Putting the gearshift in neutral, I rotated the rear wheel by hand. Fortunately I had enough fuel in the tank to tilt the bike onto its front wheel.
While turning the rear wheel by hand, I engaged the rear brake with my other hand and the wheel came to an immediate halt. This essentially exonerated both the rear axel and breaking system. Lifting the front wheel off the ground with the main-stand serving as fulcrum, it was light enough to attempt to rotate the front wheel with my foot but it didn't turn. So I lodged a stone under the sump too keep the front tyre from touching the ground. I knelt down on both knees and attempted to turn the wheel with both hands. It was stuck but I managed to turn it just a few centimeters.
I was convinced that the brake pads didn't disengage after the last time I applied it, because I could see that the pads and the disk still making flush contact. I whipped out a screwdriver from under my seat and pryed the pads away from the disk with difficult. Eventually they separated sufficiently for the front wheel to turn, though not freely. I then realized I had to ride home without using the front break because if I did, I would have to go through the painstaking prying exercise once again. This wasn't going to be fun because I would have to ride dead slow, but the important thing was to get off the road before peak hour. I needed to go slow enough not to cause much friction —thus heat— on the disks, so that it would cause them to turn blue.
Seeing I was riding down a steep decline, I engaged my clutch to attain free-run. The bike progressively slowed down and eventually came to a halt on the downhill. I then realized that either the front or the rear brakes was binding, alternatively that the front or rear axel was seizing or was at least starting to seize. I then rode the R1100RS a short distance into a side street so that I could check what the problem was. I turned off the ignition and pulled the R1100RS onto the main-stand, to get both wheels off the ground. Putting the gearshift in neutral, I rotated the rear wheel by hand. Fortunately I had enough fuel in the tank to tilt the bike onto its front wheel.
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| The right side Caliper of my BMW R100RS |
While turning the rear wheel by hand, I engaged the rear brake with my other hand and the wheel came to an immediate halt. This essentially exonerated both the rear axel and breaking system. Lifting the front wheel off the ground with the main-stand serving as fulcrum, it was light enough to attempt to rotate the front wheel with my foot but it didn't turn. So I lodged a stone under the sump too keep the front tyre from touching the ground. I knelt down on both knees and attempted to turn the wheel with both hands. It was stuck but I managed to turn it just a few centimeters.
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| Caliper pistons seized inside their sleeves |
I was convinced that the brake pads didn't disengage after the last time I applied it, because I could see that the pads and the disk still making flush contact. I whipped out a screwdriver from under my seat and pryed the pads away from the disk with difficult. Eventually they separated sufficiently for the front wheel to turn, though not freely. I then realized I had to ride home without using the front break because if I did, I would have to go through the painstaking prying exercise once again. This wasn't going to be fun because I would have to ride dead slow, but the important thing was to get off the road before peak hour. I needed to go slow enough not to cause much friction —thus heat— on the disks, so that it would cause them to turn blue.
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| The left side front Caliper of my BMW R1100RS |
When I arrived home I immediately got out my tool box and started undoing both front calipers bolts (8mm hex bolt). With the screws out, it should have been easy to twist the caliper sufficiently for the caliper pistons to recede. By doing so, the caliper could simply slip past the wheel rim but it didn't. I couldn't even twist the caliper a fraction of a millimeter. So in order to get the caliper off the disk, I was compelled to remove the 12 screws (4mm course spline) that holds the fixed part of each of the floating brake disk onto the rim on both side.
With the disk removed I still couldn't get the calipers to simply slide off. Using a small hammer, I gently persuaded the caliper to slide off the disk, a centimeter at a time, with every knock. Eventually I the had calipers off and saw that the caliper pistons were almost completely exposed. This was due to the fact that the pads had worn down to its last 2 mm. After removing the spring clips from the pin, using a thin screwdriver, I punched out the pin from the back of the caliper, that holds the brake pads in place. Normally it would be quite easy to apply thumb pressure on the pistons to get them to return into the caliper, but in my case they were stuck. They wouldn't budge.
Using a water pump pliers I managed to squeeze one piston back in, which caused the opposite opposing piston to protrude. Squeezing that piston back in, cause one of the others to protrude. Oh, forgot to say that I have calipers with four pistons in each. After playing silly buggers with the pistons for quite some time, squeezing one then the other, then the other, then the other, I decided to release the brake fluid pressure by opening the bleed nipple (bleed valve) on each caliper, so that I could get all four in the home position, and it worked.
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| Caliper pistons in their fully home position |
With the disk removed I still couldn't get the calipers to simply slide off. Using a small hammer, I gently persuaded the caliper to slide off the disk, a centimeter at a time, with every knock. Eventually I the had calipers off and saw that the caliper pistons were almost completely exposed. This was due to the fact that the pads had worn down to its last 2 mm. After removing the spring clips from the pin, using a thin screwdriver, I punched out the pin from the back of the caliper, that holds the brake pads in place. Normally it would be quite easy to apply thumb pressure on the pistons to get them to return into the caliper, but in my case they were stuck. They wouldn't budge.
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| Visible corrosion and contamination on the right side caliper nipple (bleed valve) |
Using a water pump pliers I managed to squeeze one piston back in, which caused the opposite opposing piston to protrude. Squeezing that piston back in, cause one of the others to protrude. Oh, forgot to say that I have calipers with four pistons in each. After playing silly buggers with the pistons for quite some time, squeezing one then the other, then the other, then the other, I decided to release the brake fluid pressure by opening the bleed nipple (bleed valve) on each caliper, so that I could get all four in the home position, and it worked.
I needed to get my BMW R1100 RS back onto the road as soon possible but didn't have replacement brake pads so I decided to scavenge them from my R1100R temporarily, considering I still hadn't replaced her fuel pump yet. Because my R1100R was standing for an extended period of time, the caliper pistons also became stuck, so I had to go thought the same process to get the calipers off the disks, as I just did with my R1100RS. The pads I retrieved —in he image below— weren't in such a great shape either but had sufficient life left for at least a few weeks before I would have to replace them with new which I could purchase meanwhile. As can be seen in the pics below, the padding on the pad was more-or-less the thickness of the metal to which it was bonded.
As can be seen in the image below, I managed to get the pistons fully home in both calipers with the understanding that I would have to bleed the system thoroughly. After refitting the calipers and the disks in place, I opened the brake fluid reservoir on the handle bar the add some brake fluid and found a white crystalline substance caked onto the reservoir lid. I cleaned it with a wire brush, removed the rubber insert and added the Dot 4 brake fluid, refitted the cover and started pumping the front brake. However, nothing happened, the brake lever was hard to squeeze and after several attempts I realized that the fluid wasn't pushing the pistons out of the caliper body to engage the pads with the disk.
I could wiggle the pads with my finders and there was quite a bit of space between the pads and the disks, so I stripped the calipers from the forks. This time it was easy because the space between the pads and disks allowed me to slip them past the tyre mag rim. Within a few minutes I has punched out the both pins and removed the pads. I could see that the pistons were still completely home. They didn't even budge 1 mm. With the calipers hanging loose on either side of the wheel, I started pumping the brake lever again but applied a lot more pressure to the lever. I could hear the fluid squish and there was movement on the brake lever.
After pumping a few more times, I checked the pistons but they were still in the home position. Then I noticed that something dripping from the black portion of the front mudguard, the portion closest to the engine, It was brake fluid and it was coming from somewhere under the front portion of the mudguard. After removing the mudguard, I once again squeezed the brake lever and saw brake fluid squirting out from the rubber pipe that connects to the caliper, but close to the end that mates with the brass T junction located in the root (pilca) of the fork..
I needed to remove the rubber hose, so I undid the banjo bolt that connected it to the brass T junction bolted to the pilca. The entire hose can be seen in the image below. The Banjo bolt was really tight and I thought that my spanner slipped when it turned but it loosened the bolt. As expected, the brake fluid was gushing out so I took a clean white cloth to soak up the fluid.
Very surprisingly, I found several black rubber particles in the cloth that soaked up the break fluid. So I removed the other banjo bolt attached to the caliper and removed the nipple (bleed valve) and several larger pieces of rubber came out of the holes in the caliper. To make certain the holes in the caliper wasn't obstructed, I decided to split the calipers and clean them out, as can be seen the the images higher up above.
Since there was a fair amount of rubber particles that flowed from the T junction, it meant that the rubber residue had to come from the hoses closer to the brake fluid reservoir. So I loosened the banjo bolt connecting the feed hose to the T junction. As can be seen below, the braid fluid is gushing out.
Looking at the banjo bolt from the supply rubber hose, there was a huge piece of rubber completely blocking its jets, as can be seen below. I was then convinced that all the rubber hoses were disintegrating due to the corrosive nature of the break fluid. So there was no way I was just going to only replace the ruptured rubber hose that connects the right side caliper. All of them had to be replaced. Since there was no leaks in the system before I started working on my R1100RS, the force with which I squeezed the brake lever must have popped the rubber hose connected to the right side caliper.
My intention is to replace all the rubber brake lines on my R1100RS with Du Pont Teflon brake hoses clothed in a flexible Stainless Steel sheaths. I came to find out that when the rubber lines get old and the brakes are applied, instead of the non-compressible fluid pushing the pistons out of their sleeves, the aged rubber brake lines start to balloon, thereby reducing the effectiveness of the brakes. I therefore appeal to each and every BMW rider, or for that matter every motorcycle rider, to be safe and check their rubber brake lines for disintegrated rubber particle and if any replace them all. As a safely measure the Dot 4 fluid also needs to be replaced at least once every year. Hopefully any problem with the rubber brake lines would show up within this interval. Safe riding fellow BMWers, until next time.
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| Brake pad lining relatively the same thickness of its backing plate |
As can be seen in the image below, I managed to get the pistons fully home in both calipers with the understanding that I would have to bleed the system thoroughly. After refitting the calipers and the disks in place, I opened the brake fluid reservoir on the handle bar the add some brake fluid and found a white crystalline substance caked onto the reservoir lid. I cleaned it with a wire brush, removed the rubber insert and added the Dot 4 brake fluid, refitted the cover and started pumping the front brake. However, nothing happened, the brake lever was hard to squeeze and after several attempts I realized that the fluid wasn't pushing the pistons out of the caliper body to engage the pads with the disk.
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| Half of a brake caliper held together by 4 hex screws. The capillary seal clearly visible. |
I could wiggle the pads with my finders and there was quite a bit of space between the pads and the disks, so I stripped the calipers from the forks. This time it was easy because the space between the pads and disks allowed me to slip them past the tyre mag rim. Within a few minutes I has punched out the both pins and removed the pads. I could see that the pistons were still completely home. They didn't even budge 1 mm. With the calipers hanging loose on either side of the wheel, I started pumping the brake lever again but applied a lot more pressure to the lever. I could hear the fluid squish and there was movement on the brake lever.
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| Half of a brake caliper held together by 4 hex screws |
After pumping a few more times, I checked the pistons but they were still in the home position. Then I noticed that something dripping from the black portion of the front mudguard, the portion closest to the engine, It was brake fluid and it was coming from somewhere under the front portion of the mudguard. After removing the mudguard, I once again squeezed the brake lever and saw brake fluid squirting out from the rubber pipe that connects to the caliper, but close to the end that mates with the brass T junction located in the root (pilca) of the fork..
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| Burst Brake line |
I needed to remove the rubber hose, so I undid the banjo bolt that connected it to the brass T junction bolted to the pilca. The entire hose can be seen in the image below. The Banjo bolt was really tight and I thought that my spanner slipped when it turned but it loosened the bolt. As expected, the brake fluid was gushing out so I took a clean white cloth to soak up the fluid.
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| Burst break line |
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| Rubber particles from the rubber break lines |
Since there was a fair amount of rubber particles that flowed from the T junction, it meant that the rubber residue had to come from the hoses closer to the brake fluid reservoir. So I loosened the banjo bolt connecting the feed hose to the T junction. As can be seen below, the braid fluid is gushing out.
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| Dot 4 brake fluid gushing out of the T junction |
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| Banjo bolt with a clogged jet. |
The ruptured hose popped at the point it did, because the rubber wall at that point provided the least resistance to pressure. This could have happened whilst I was ridding and the possibly the cause of a horrific accident. I contacted BMW to get a replacement set of brake lines and was advised that they needed to be replaced every 4 years. I was blown away, I've only had the R1100RS for 17 months and expected those hoses to have been replaced by its previous owner but they looked like original equipment since manufacture 19 years ago.
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| Reassembled caliper with rubber residue in the banjo bolt hole |
At this point I still didn't get the pistons to budge, so I reassembled the calipers, cleaned and fitted the nipples (bleed valve) then connected the supply rubber hose between the forks directly to the one of the calipers and started pumping the brake lever. I needed to add Dot 4 brake fluid and thereafter continued pumping. Gradually the pistons started to move. First one, started protruding then another but they didn't move with ease. My idea was to clean the pistons on the one caliper first, then disconnect from the supply rubber hose then connect the other caliper and do the same.
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| Reassembled caliper with rubber residue in the banjo bolt hole |
Short of buying a caliper service kit and replacing all the rubber seals, I went and bought a can of Wynn's Brake and parts cleaner with which to clean the pistons. I sprayed each piston several times but it made no difference. So I removed the pistons individually and cleaned the piston well thoroughly with the spray. However due to time constraints, I could complete the entire job and left it for the following day. I was probably best, so that I could at least go purchase the necessary hoses and brake pads.
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| Wynn's heavy duty brake and parts cleaner |
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