Please help. Made a video of my brake-dragging problem.

[Smellii]

Almost to tears about my brakes. Made a video of my problem. Brakes dragging bad after I cleaned everything.

http://www.youtube.com/watch?v=KLip-k_AqjA&feature=youtu.be

Should I use special lube for the pistons? If so will motor oil or WD40 work? How best can you clean the tiny fluid return hole in the front master cylinder? I have an air compressor; can I use that?

[BassCliff]

Hi,

Should I use special lube for the pistons? If so will motor oil or WD40 work? How best can you clean the tiny fluid return hole in the front master cylinder? I have an air compressor; can I use that?

Use only brake fluid on the pistons, no "special" lube. You do need special lube for the caliper axles, caliper grease, usually a copper-silicone grease is the best. But any Gunk or Permatex caliper grease will do just fine.

There's a tiny hole in the bottom of the master cylinder. It's not the larger hole that you might see, because the tiny hole is usually hidden by a baffle. You have to take the master cylinder apart and poke a very small wire through the hole to get the gunk out of there. Then spray well with brake cleaner. Re-assemble, fill, bleed, and ride safely.

Thank you for your indulgence,

BassCliff

[hampshirehog]

Ditto Cliff - only use brake fluid only. NOTHING ELSE (worth shouting....).

The tiny hole is really tiny and you may not even be able to see it. There's a small hole you can see (even if your eyes are not that clever like mine) - there's a smaller one. I use a magnifying glass.

You may have trouble with crap in those old lines. If they are the originals I would advise swapping for new stainless; it's night and day difference on brake feel as well. The fact that the brakes tighten up when you have been for a ride (and warmed things up) suggests crap in the line, or at the very least water (which can be catastrophic).

Plus the guy on YT is right - your fluid level is very low.

[Nessism]

You only did half the rebuild job; the master cylinder needs to be cleaned and the brake lines replaced. Did you use caliper grease on the sliding pins?

Some brake/wheel drag is normal, particularly on the rear of a shafty. Your brakes look to be dragging a little more than normal but not an unusual amount for a freshly torn down system - the caliper parts mate together as you ride the bike. The fronts in particular need some miles before everything will settle down. Try taking out the bike and dragging the brakes while using the throttle to bed in the pads. That should help the situation some assuming the master cylinder isn't plugged up.

Good luck and please plan to finish the rebuild properly when you have time.

[Smellii]

Thanks guys for helping out. You are not going to believe this but I fixed it. I greased up the caliper axles per Basscliff's and Nessism's advice, poked around in that tiny-er hole in the master cylinder with a bristle from a metal bristle brush (but I don't think it was clogged because I saw it back flow fine when bleeding) -thanks hampshirehog, and scrubbed and lubed all the sliding parts in the caliper assembly (metal sliders and the back of the brake pad (per manual)). All this fixed the front only because when I came back from a spin around the block my back caliper was SMOKING (and stinky).

(So I proceed to walk around my bike pretending to look smart pressing on various parts.)

In doing so I happen to press on the rear brake peddle and it seemed to have no range. Turns out that adjusting screw on the rear brake pedal was way to tight. From this I deduce: Before I worked on my calipers it was in the correct position based on the state of the components at the time. However, I should have loosened it completely before bleeding/adding new fluid and before building pressure again in the lines. Unscrewed it and all the pressure was relieved from the rear rotor. (perhaps the caliper rebuild guide should add to check for this seemingly insignificant detail ???)

I do know, however, I need to replace/rebuild the other half of the brake system but have to make due with what I have because I'm as poor as one person can be at the moment. As soon as I can I will though. Thanks for pointing that out, Nessism.

I love love love this forum and the website. Use them aaaaallllll the time. A thousand thank yous!

[verboseone]

Great thread! Thanks guys!
Thanks for the update. I wouldn't have thought to check the adjustment on the rear brake pedal either.

[jaywelchy]

(So I proceed to walk around my bike pretending to look smart pressing on various parts.)

You got the right attitude, and your welcome in my garage anytime!

Jason

[TheCafeKid]

If you've not replaced the hoses, as Nessism has suggested in his Top 10 Mistakes link, please do so. The rubber lines were scheduled to be replaced every 2 years. I've never ever seen them replaced. Ever. Including by my self unless they got ripped off for stainless lines (highly suggested, not only better, but cheaper than OEM). The lines will not only expand as they age, but they can also collapse, preventing back-flow and overpressurizing the system causing symptoms you describe as well.
As to bedding in your pads...
There are as many theories on proper bedding as there are people to tell you about them, so I'm not going to say what Nessism is suggesting is wholly wrong. But I will respectfully disagree. As has been explained through a couple of sites, and links on this very board, a method that I have used pretty much every time and has always worked is a bit different than Eds suggestion.

Some gear-heads would suggest that what Ed is describing as a break in proceedure would actually cause glazing of the rotor and the pad. Leaving trace amounts of pad material embedded in the rotor, causing chatter, un-even wear, poor lever feel etc etc.
The method I've used requires you to slow from around 30 MpH to nearly stopped, without stopping, and then immediately speed up to 60, then on the brakes hard (but don't kill yourself) to a near stop, then back to 80. Again, slowing hard (hey, you can use this as an opportunity to practice emergency braking) and then back to thirty. Repeat the process once more.
The theory is it properly heats the pads and discs to allow bedding, but also allows both to cool as to prevent glazing, and stopping completely is a no no as it will leave said pad deposits on rotor. Just one of many theories, and as I said they're about as good as opinions....

[Steve]

Ed's version of brake bedding isn't really all that different.

It heats the pads to bed them, just like yours. The only difference is the number of times and the duration/temperature.

I have seen a variation that includes both methods. Drag the brakes a bit to warm them up, then speed up and use them moderately hard a few times. Just don't do the "moderatly hard" stops on cold pads.

.

[Normk]

Smelli, your rear pedal adjustment was likely placing that master cylinder piston too far forward in the bore such that the compensating port was not open to the forward portion of the cylinder. You likely already know this but in case someone is not aware, there are two small/tiny holes in the bottom of brake master cylinder bores which lead downward from the reservoir into the piston bore.

The hole which is further forward and is the subject of the reference in this thread is called the compensating port. This is usually obvious because it typically has a structure around it such as a plastic/metal deflector. When the brake is applied, this is accomplished by applying mechanical effort to press the brake master cylinder piston forward into the master cylinder bore. The forward movement displaces fluid.

Some close observation of a normally adjusted and operating master cylinder will reveal that there is some flow out of the compensating port into the reservoir during the initial movement of the master cylinder piston but the flow stops after a short movement of the piston.

As the piston moves forward into the master cylinder bore, it displaces fluid and, initially, the fluid moves upward out of the piston bore into the reservoir which can usually be observed as a disturbance in the reservoir fluid. In some cases the fluid will squirt upward with some force.

As the master cylinder piston moves further forward, the piston rubber seal passes the compensating port which is then sealed off from connecting the bore ahead of the piston into the reservoir.

It is from this point onward that the master cylinder piston movement pressurizes the brake system which is intended to apply pressure to the brake caliper pistons, wheel cylinder pistons (in drum brakes), clutch slave cylinder piston (in clutch systems), or ABS components, etc.

When the brakes are applied, the purpose of the brakes is manifest and, if the machine is in motion, the friction resulting from the action of the brake friction material acting with the rotor or drum begins the conversion of kinetic energy into heat which, in part, enters the brake friction material (pad or shoe) and transfers into the caliper or wheel cylinder.

Increasing temperature within the caliper or wheel cylinder causes the brake fluid to expand, but this is not usually observed by the rider. The amount of expansion of the fluid can be quite significant evidenced by the following experiment.

If one adjusts the master cylinder piston's return (battery) position so that the piston is unable to return past the compensating port and then the brakes are operated, the expanding fluid will, as before, expand within the caliper. The expansion will, if application is continued sufficiently, apply the brake when the piston has been released because there is no mechanism available to release the pressure.

This expansion, manifest by pressure will continue to apply the brake which will continue to convert movement to heat and continue to heat the fluid. In the case stated in this thread, this is the likely cause of the dragging rear caliper.

In extreme cases, the bike will be dragged to a stop and be unable to move until the system has cooled enough that the fluid contracts to the initial volume at the time that braking began.

We used to see this frequently when 1970's Fords had a master cylinder replaced onto power brake boosters. If the power brake booster's push rod were not properly adjusted, the vehicle would often be found on the roadside.

This condition can also occur, as I think someone suggested in an earlier post, if the compensating port is blocked.

So what is supposed to happen if the piston is adjusted to the proper return position and the compensating port is open?

When the port is open, on release of the piston, the port will open to connect the reservoir to the piston bore such that pressure within the bore will disperse due to fluid flow back from the bore into the reservoir. If braking heat causes (when it causes) expansion of the brake fluid within the caliper (wheel cylinder or in the clutch slave), accumulated pressure will release on return of the master cylinder piston.

If the master cylinder reservoir is over filled, pressurizing of the brake system will occur in a similar manner.

Another concern regarding the compensating port needs mention: If the reservoir lid is not in place when the brake is applied and rapidly released, a squirt of fluid my be discharged upward with enough velocity to escape the reservoir. The resulting spray can distribute brake fluid widely onto surrounding areas resulting on damage to paint and other surfaces. Many have paid this price.

In master cylinders which have some wear to the sealing cup or cylinder bore, or are simply gummed up by deposits, there may be enough leakage past the piston cup on release to vent the fluid back so all may appear to be well until such time as something such as a master cylinder service or even pad change affects the condition. This is why dragging brakes sometimes occur after some other intervention.

Of course, misaligned caliper mountings, binding caliper pistons, too think brake pad material and many other factors can cause brake drag. One clue to the possibility of a blocked compensating port is to open a bleeder nipple when the brake drag is manifest because opening the nipple will release the accumulated pressure. Opening a nipple will not alleviate a binding mount and so on.

The other master cylinder port, just to close this subject to some degree, is the breather port. The compensating port "compensates" for differences in fluid volume within the system while the breather port's purpose is to vent fluid from behind the master cylinder piston when the piston is returning to battery on release.

If some means is not provided to release fluid which has accumulated behind the piston, the resulting pressure can cause slow release in some cases but almost always earlier leakage from the piston bore as the piston end seal is over powered by the pressure. A seal in top condition can withstand this but as time goes on leakage can occur.

If someone is interested, remind me to discuss the "pump-up" action of the piston seals on rapid and repeated application as well as the role of rapid application in sealing a compromised seal.

HIH, time to get some work done,


Norm

[cowboyup3371]

HIH, time to get some work done,


Norm

I finally figured out what you are saying here...HIH = Hope it Helps.

Wow, I'm getting old.

[BigD_83]

I finally figured out what you are saying here...HIH = Hope it Helps.

Wow, I'm getting old.

Cowboy...I've been wondering the same thing. Guess who doesn't carry a cell phone or text message? Hmmm, maybe I AM getting old.

[BigD_83]

Great writeup, Norm.

I am definitely interested in what you have to say about "pump up"

[tkent02]

Great writeup, Norm.

+1, keep them coming.

[Smellii]

I must say. I'm impressed of your knowledge and more impressed of your willingness to share. Thanks for teaching me how to fish when it comes to my brakes. You, Sir, get a gold star.

BTW. Took it out on the road today. Absolutely no problems and being able to smoothly coast without dragging is a wonderful thing. Brakes work great.