Dan M

I've seen deteriorated brake hoses leave charcoal like substance behind. I've also seen faulty hoses collapse internally causing a restriction to the flow of the fluid returning to the master. Many people will condemn a caliper as seized only to find out that once the caliper is removed it moves freely. (perhaps now we're getting somewhere) That would not explain no further trouble if the hose was not changed though. The quick check for a restricted hose is with the wheel off the ground, pump the brake lever, if the brake is dragging after release of the lever, open the bleeder and see if the drag is relieved. Obviously done after the linkage is checked for free play insuring the master is fully extended. This may be a car only problem though, as front brake hoses on a car flexes a great deal more in their service life.

Sorry, somewhere in the depths of one of your posts I thought I recalled a hypothetical theory of too much fluid in the reservoir holding the piston off of the relief port. I just went back and skimmed over paragraph after paragraph and didn't see it. You did tie in the unlubed brake lever linkage acting conspiratorially with the air and water and grunge setting the chain of events into action. Maybe I was falling asleep while reading all that stuff late one night and didn't get it. I guess I just don't buy vapor in the system applying the brakes to the point of lock up. I've seen water saturated fluid many, many times in my career and it always caused loss of brakes and I've never seen it apply the brakes. I'm sure even after 30+ years doing this sort of thing, I haven't seen everything, but even at the current rate of over 20 brake jobs per week, I've seen quite a few different scenarios but not this one. Not yet anyway. It seems too far fetched or at least too isolated an event to be the cause of this tight brake condition posters are complaining of. Like I said earlier, The big #3 is far more likely most people's trouble. Edit: One more thing, If, as you think may have happened, the unlubed linkage was holding the piston of the master partially depressed, that's all he'd need to get his brake red hot. Especially if he's the kind of guy to try to "ride out of it, using lower gears and more throttle" No air or water vapor needed to lock things up. No different than riding for several miles with your boot resting on the pedal.

Sean, Thank you for your selfless, steadfast dedication to this thread.

In reference to the big 3, the culprit, I'd guess by a considerable margin is #3. Not only grunge around the piston but also at the edges of the pads where they ride in the caliper. These pads are a tight fit in the caliper, They are positioned low and have a cap over them helping brake dust and other contaminants collect. They have a noted history of binding (the famous rear brake groan). Water contamination may play a roll if the reservoir is over filled. If the rider is checking / filling the fluid (for it to be overfilled to begin with) he's probably eliminating the water anyway. Enough water in brake fluid to allow boiling makes for some very dark fluid. I'd hope he would notice and not just fill it to the brim. In any case if it does get to this point, he will notice a spongy pedal before anything else happens. Has anyone with this catastrophic failure reported this loss of brake action before the lock up? And if there is vapor in the system, it will be at the hot spot (the caliper) so there will be no or low hydraulic pressure against the pads. This may cause overheated brakes but not likely a complete lock up.

The master starts to move fluid as soon as the piston is moved. How far it needs to go before braking action is realized, is determined by how far the pistons needs to move to apply pressure to the pads. The square cut seal relaxes when the hydraulic pressure is relieved, pulling the piston back very slightly. The pads always are in contact with the rotors, there is no mechanism to retract them when the caliper piston retracts. There is just no pressure against them. There will always be some heat generated however slight. I wouldn't be concerned by "warm", it doesn't take much drag to become too hot to hold your hand against.

On any caliper there is an inside, square-cut seal that is the hydraulic seal and an outside seal, either boot type or lip who's function is to keep dirt (dust) off of the inner seal & piston. Sorry if I'm using automotive terms (dust boot) but that is what I've called the outer seal, regardless of type for 30 years. Usually on larger calipers it is a boot but as you stated Jack, on the little Brembo it is a seal. As for a piston's coating, be it chrome plating or anything else, just how hot does the piston need to get to lift the coating? Glowing red? How do the seals cope with these temps without complete failure? I've never seen a caliper piston's surface damaged by anything other than rust. If it lifted could it have been faulty to begin with? The ability to notice a dragging brake certainly depends on what kind of riding you are doing at the time. During a long stretch on the highway, it may feel like no more than a headwind robbing you of power and go unnoticed. In slower or stop & go riding, indicators like noises, odor, and strange handling would have to be ignored for awhile. Back to the free play issue, go out to your bike and feel by hand how much downward force on the brake lever is needed to overcome the master cylinder's internal spring. I haven't measured it with a fish scale but I'd guess it is at least a pound. If there is free play in the linkage, no additional springs are needed and no bumps are going to activate that brake (unless of course your boot is resting on it) I'm thinking most of these troubles are dirt & brake dust related. It doesn't take much to bind the pads. I wonder if things would stay cleaner if the little plastic cap was removed, allowing more air to circulate.

I agree with all of this Martin. When inspecting the caliper it will be obvious if there is trouble before reassembly. (condition of visible dust boot, how smoothly the piston retracts...) And yes contrary to popular belief if any brake is dragging enough to overheat, it would be tough not to notice before it got so tight as to cause catastrophe.

Not likely thers's enough weight in that lever to apply the brake. The internal spring in the master has considerable force. It may be that the lever return stop or linkage is out of adjustment and there is no free-play. This coupled with heat expansion can cause dragging. I agree with Ratch that a rear brake failure can be dangerous. While I do 90% of my stopping with my front, and the likelyhood of a rear failure is remote, and I think I'd notice if it were dragging before things got hairy. If the seals failed from severely overheating and dumped brake fluid on my rear tire, that may be cause for concern.

The rubber tipped style is hard to seal against the head but not impossible. I'd wonder about the quality of the gauge and accuracy of the readings so don't let your results justify a tear down! That said, it can be used for comparing side to side. Start by disabling your ignition or grounding your plug wires. Open your throttle and press the gauge into the plug hole with sufficient force that you hear no seeping of pressure on the compression strokes. Watch the needle while cranking the engine. After it bounces 4 times it will probably not move much further. Keep the count the same from cylinder to cylinder. Compere the results to the other side. I doubt you have 20% difference.

Just another note - 4 compression strokes when testing compression. 20% difference is a lot

Hard to imagine how a spacer will change a squeak. The 02 fork has more range of damping adjustment, don't know if there are other differences. I don't have much dive trouble with the Wilbers springs and 100mm air gap. (or "luftkammer" as Ratch so much likes to say) I did have to increase the spacer size considerably to get proper sags and I keep the compression damping closer to the low (soft) end of the range. This month's Motorcycle Consumer News has a good article on suspension set up. Nothing that hasn't been covered by the "technical collective" here but it is good info and all in one place.

Right on Docc, Further proof is to increase engine speed to about 2500RPM and watch the movement decrease as the slack is removed from the chain.

When you need to use thread locker (don't make a habit of it everywhere - I've never seen a transmission cover loosen without it) Run a small bead of the stuff around the bolt a couple of threads up from the bottom. It will smear it self to cover a few more threads as you screw it in. Do not cover all of the threads, you'll have a mess and a very difficult to remove bolt.

Family values - rubbish, and, don't even say the words warm, cold, life or choice. This is a Motorcycle forum! (unless of course your are speaking of cold idle quality or warm tires or riding is the passion in your life and it's your choice to ride instead of drive....)

Good link hackster.

Any day on a motorcycle in Tuscany does not suck

Nothing wrong with making a bike a better, more comfortable fit. Unless of course, you enjoy discomfort.

Great trip Gil. Nice photos & story.

I love mine too. The Motobits foot controls that Greg sells work great with the risers. They move your feet forward & lower as the risers move your hands up and back. The result is your whole body rotating back some for a much more comfortable all day ride. Add the Rich Maund saddle and you'll have a touring bike.

Leave the nut alone. It can't go out of adjustment on it's own. You'll find it difficult to get perfect with the side plate on the bike, necessitating lots of trial & error. If you take the plate off it is a different story. Then you can measure where the actuator is between the dogs and set it properly. I'd think it is very close at the factory setting.

Better than beef broth! The clutch fluid moves more than the brake fluid. On the squeeze, the fluid in the clutch master drops more than the brake fluid. With that drop, air and the accompanying moisture are drawn into the reservoir, and pushed back out on the release. It is not a lot but this "breathing" of the reservoir is enough to introduce more moisture into the fluid than on a braking set up. It is moisture that darkens the fluid. I generally change mine annually which may be overkill with our shortened riding season. Color of the fluid is a good indicator, anything darker than caramel should be changed.

The best epoxy I've used for aluminum is Hysol 608 by Locktite. It is a slow cure so not good for roadside repairs but adhesion and strength are excellent.

Righto Pete. Is is an area where people need to be meticulous. Doing it the way you do is perfect, I worry about the guy who has a heavy trigger finger and sprays enough to spatter some on the other rotor. Cleaning up after is everything. Dry Teflon or PTFE lube is great for this application, the liquid aerosol that carries the lube evaporates leaving a dry almost powdery film. It doesn't attract dirt so things stay nice longer.

First off, I would not spray any WD40 or other penetrant anywhere near my brake pads. The stuff we use is identical to sil-glyde, (possibly repackaged) by 1st Ayd chemical. they call it "High-Temp silicone brake/caliper lube & dielectric grease" Under the recommended use for disc brakes they list: "caliper slides/sleeves; pad/caliper contact points; rubber bushings/pins & o-rings; metal side of brake pads. We are in the habit of using this stuff where I mentioned in my 1st post, and have never had a problem with it not staying put. I'll add that we service all of the local police cruisers who's brakes regularly come in with the rotors blue from overheating. So the stuff stands up to heat. As said before, use sparingly, too much of anything is trouble. I think you were the one to coin the phrase "bath tub caulker" in regards to someone and their liberal use of silicone sealant. Same goes here. On your floater buttons, try to find a PTFE or Teflon dry lube. (KEEP THE STUFF AWAY FROM YOUR PADS) Spray it on the buttons, let it dry, wipe your rotor faces with brake clean and you're done. I would worry about penetrant weeping onto the braking surface from centrifugal force.