Front brakes stick

Yes slide pin's are free. What could it be? Caliper block rings need to be renewed?

Andy Lishious wrote: Yes slide pin's are free. What could it be? Caliper block rings need to be renewed?

Maybe the relief port between m/c bore and reservoir is clogged, whereby pressure remains in the line after brake application is released.

Good Fortune!

Excellent hypothesis, My brake res was very diry and sludgy... beg my pard. Ill Take it apart in the am and r&r the sum bitch.

Has this bike been sitting? It would not hurt to bleed all the fluid out.

Sometimes when bikes sit and there is a change is tempurtures back and forth water forms in them like gas tanks and when you start riding the waster boils. I always carry a wrench with me when I try a bike out that has been sitting.

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Bike was sitting outside over the winter time tarped up. Brakes where serviced about year ago. Pad slap and fluid flush. Brakes don't always stick it when i start using them is when the problem occurs. Brakes get tighter and tighter.

What have you been doing to correct the situation? I mean, if you start off with the brakes fully released, and as you ride the brakes don't release causing them to grip the disc more and more each time you apply them, how do you get them to release and start the process over again?

Look inside the master cylinder reservoir, at the bottom should be two(2) small holes, both should be clear, otherwise, the brakes may not release.

Also, read this:

HEL Performance Brake Doctor - Bleeding The Braking System

Experienced bike owners and mechanics will tell you that brake bleeding is easy. It is, but there is plenty of potential for error. Reading this guide will not turn you into an expert overnight. We have made every attempt to be accurate and easy to read but we cannot impart the gifts of skill, experience and common sense. If after reading this page you feel inclined to carry out bleeding to the braking system of a bike we will not accept responsibility for what happens next. You are responsible for your own actions and this page has been placed online to only offer an introduction into bleeding. We will obviously be happy to answer any questions you may have via brake doctor.

What you will need...
Even though it is possible to bleed bike brake systems on your own it's advisable and much easier if two people do it. You will need clean, fresh brake fluid which has been allowed to settle over night - do not shake the bottle before starting as this will put air bubbles into the fluid, a length of plastic tubing which fits tightly onto the bleed nipple and a glass container so you can see the air being expelled from the system.

It's a good idea to cover any areas around the master cylinder and the bleed nipples to protect from accidental spillages. The area around the master cylinder and the bleed nipples should be as clean as you can get them as there is no point getting dirt into the system.

Firstly you need to remove the old lines so attach the plastic tubing to one of the bleed nipples and open slightly so you can pump most of the old fluid out before you take the old hoses off. It's not unknown for the bleed nipples to be seized in the calipers - mild steel nipples and alloy calipers will suffer electrolytic corrosion naturally and winter salt in the UK will only increase the effect. You may want to take the opportunity to replace the mild steel nipples with stainless steel ones.

Assuming that you have been able to undo the bleed nipples make sure the brake reservoir has plenty of fluid in it and then rest the cap back on top to stop fluid squirting out when you begin bleeding.
Priming (Filling) The System


If you have a twin disc system bleed one caliper at a time. Attach the tube to the bleed nipple and place the other end in the clean glass jar. Poor some clean brake fluid into the jar so the end of the tube is submerged so you don't pull air back in to the system.

Then open the bleed nipple, squeeze and release the brake lever slowly to give the master cylinder enough time to suck in fresh fluid from the reservoir.

Keep an eye on the master cylinder reservoir and make sure the fluid level does not fall below the minimum mark else you will start sucking air into the system. Fluid may be being pulled into the system from the jar and you may see the level drop - this is fine but again make sure the end of the tube is always immersed in fluid. It shouldn't take too many lever actions to fill the system. Tighten the bleed nipple when finished.

Bleeding The System
Open the bleed nipple slowly - you should only need half a turn and at the same time slowly and smoothly squeeze the brake lever in (or push the brake pedal down). Hold the lever in and you should see air bubbles or fluid being expelled into the jar. Old brake fluid looks foul and can be any colour from dirty white to brown or black. Movement of fluid and/or bubbles will continue for a second or two, close the nipple and then release the brake lever. Check the fluid level in the reservoir and top up if necessary. Repeat this operation until no more bubbles appear and the fluid coming out is clear.



If you have a twin system repeat this process with the other caliper (it's best to do the furthest away from the master cylinder first) If everything has gone okay you should now have a brake system with a good solid feel to it, the lever will travel a short distance and then a solid resistance will stop it moving any further.
If when you continue to apply pressure you get a slow movement or spongy feel to the lever it's a good sign that there is still air in the system. There are a number of possibilities not least that you didn't get all of the air out of the system so you should start bleeding again. Tighten all parts to the correct torque setting and then check the whole system to see that the lines are not trapped on full lock, no fluid leaks from anywhere etc.



Troubleshooting:
Not all calipers have there bleed nipples at the highest point on their anatomy. This means that if there is a small pocket of air trapped above the nipple it will be hard to remove (air always goes to the highest point of the area it is in) and make the system spongy. You can get around this by taking the caliper off and making sure the nipple is at the highest point but remember to put a spacer in between the pads to stop the pistons popping out and making it easier to refit the caliper.

A similar problem occurs with some racing bikes which have steeply angled handle bars - the brake hose arches up above the master cylinder and a small pocket of air can get trapped here. Again you can rearrange the layout or you could inject brake fluid using a syringe very carefully and slowly in through the bleed nipple in the caliper bearing in mind that the fluid in the reservoir may overflow. Fitting a banjo bolt which incorporates a bleed nipple to the master cylinder and bleeding this first before the rest of the system is another way to fix this problem.

If you are unable to remove the sponginess no matter how carefully you bleed the system you may have a sealing problem which you will need to consult your local dealer about.

The master cylinder is fed from the reservoir by a tiny hole and this hole easily gets blocked which is why cleanliness is so important when bleeding brakes. If you cannot bleed your brakes yourself make sure you talk to your local dealer and get them to do it for you.

Don't be tempted to use any of the 'self bleed' gadgets unless you really, positively, nothing else for it, have to. These things allow the nipple to be kept open as they incorporate a non return valve to stop air re-entering the system. But the bleed nipple has a threaded end which screws into the caliper - air can be sucked into the caliper along this route if the nipple is loose in the threaded part of the caliper - it will only be a small amount but why do it in the first place as we are trying to remove air...

When you have successfully bled your brakes make sure both bleed nipples are done up tightly, all banjo bolts are done up tightly and top up the reservoir. Do not overfill the reservoir as this can cause hydraulic locking of the system preventing the pistons in the caliper from fully retracting - this causes binding of the brake.



Re check the system visually before test riding - and we mean test riding. Just go forward a few feet slowly and apply the brakes then bring the bike back into the workshop to check that their is no fluid leaking from the system, everything is done up correctly and the brakes have a good solid feel to them. Do not ride your bike until you are certain you have bled the brakes correctly - If in doubt get your local dealer to bleed the system for you.


Troubleshooting And Trade Secrets!!!
Bleeding brakes like many things is a skill and with some modern master cylinders being mass produced sometimes rough areas within them can catch and air bubble which you simply can't remove with normal bleeding procedures. In these cases you can use our handy 'trade secrets' which may well help.

1. Tying the lever back overnight
One way to rid any last remaining air from the system is to tie back the lever over night. Firstly remove the master cylinder reservoir cover BUT then balance it back on top of where it should be fitted so that moisture in the air does not contaminate the system overnight. Then pull the lever in as hard as possible and cable tie it in the ON position (brake lever pulled right back to the bars). Leave this overnight and in the morning release the lever and your brakes should feel fantastic - basically the back pressure caused by tying the lever back overnight will have forced any last remaining air out of the system out to the atmousphere and leave you with sharp brakes the next day. Replace the reservoir cap correctly and you are ready to ride.

2. Priming the system the easy way
You will have read above the normal way of priming the system but another way (used by many professionals) is to connect the hoses to the master cylinder as per normal but instead of fitting them to the calipers you simply put the caliper end or ends of the brake lines INTO the reservoir at the top so that the banjo holes or fitting hole is beneath the surface of the brake fluid. Make sure you have towels etc covering all areas around the master cylinder in case of spillage etc. SLOWLY pump the system in and out (not fast as brake fluid will squirt out over paintwork etc) as this 'circuit' will completely fill the hoses with fluid making bleeding much easier afterwards. On the final 'squeeze' of the lever leave it on (fully pulled in) and tie it back. Remove the hoses from the reservoir and wipe off all excess fluid. Then connect them to the calipers at the correct torque and then release the lever. Bleed as normal but with the added benefit of the lines and master cylinder being air free to start with!!!

3. Reverse Bleeding
Although we aren't fans of this type of bleeding I do include it here as many bike shops use this themselves - the only thing I would say is if you push the fluid in too quickly you can pop brake caliper seals etc so slowly and low pressure are the key words here!!!

For this you will need a large syringe filled with new fresh brake fluid and a tube which fits the bleed nipple and the syringe. Connect the syringe tube to the bleed nipple and open the bleed nipple - SLOWLY push the brake fluid in through the caliper up to the master cylinder (which is bleeding in reverse) Do the caliper furthest from the master cylinder first and then the other one. Repeat if necessary and keep checking the reservoir level so you do not overfill the system. This way ALL AIR IS PUSHED UP AND OUT OF THE SYSTEM meaning bleeding is much easier than trying to push air DOWNWARDS and out of the system in conventional bleeding BUT please do not exert massive pressure at the caliper as this can pop seals etc.

Ride Safe.

And:
www.webbikeworld.com/Motorcycle-technica...otorcycle-brakes.htm

DOT 3 VS DOT 4 Brake Fluid

I just flushed my brake lines with new DOT 3 fluid only to find out that the master cylinder has a leak. Instead of rebuilding the master cylinder, I bought a 'newer' used MC off of ebay, but it calls for DOT 4 instead of DOT 3! D'oh! Well, I've heard that 3 & 4 are very similar and I'm wondering how thoroughly I need to flush the DOT 3 fluid out of the brake lines? Can I just 'push' the DOT 3 fluid out by adding DOT 4 to the master cylinder and pump until I think I have all of the DOT 3 out of the lines? How would you do it?

...Can I just 'push' the DOT 3 fluid out by adding DOT 4 to the master cylinder and pump until I think I have all of the DOT 3 out of the lines? How would you do it?

YES. That method is just fine. Same for the routine "flushes" without requiring re-bleeding from scratch.

I use a rubber squeeze syringe to remove most of the existing reservoir fluid, but leaving the bottom ports covered with fluid so as to avoid air entering the line. Then fill with new fresh fluid, pump it through (always leaving the bottom ports covered with fluid so as to avoid air entering the line) and repeat refilling and pumping until the new fresh fluid exits the bleeder valve.

Patton

Brake Fluid Problems

"I like to go with DOT 5 fluid when I rebuild the brakes, just a better product"/quote]

Maybe not better, but certainly different. An alarm went off in my brain, so I Googled this up.

"More than you ever wanted to know about brake fluid....

Brake fluid facts

By Steve Wall
As a former materials engineering supervisor at a major automotive brake system supplier, I feel both qualified and obligated to inject some material science facts into the murky debate about DOT 5 verses DOT 3-4 brake fluids. The important technical issues governing the use of a particular specification brake fluid are as follows:

Fluid compatibility with the brake system rubber, plastic and metal components.

Water absorption and corrosion.
* Fluid boiling point and other physical.
* Brake system contamination and sludging.

Additionally, some technical comments will be made about the new brake fluid formulations appearing on the scene.

First of all, it's important to understand the chemical nature of brake fluid. DOT 3 brake fluids are mixtures of glycols and glycol ethers. DOT4 contains borate esters in addition to what is contained in DOT 3. These brake fluids are somewhat similar to automotive anti-freeze (ethylene glycol) and are not, as Dr. Curve implies, a petroleum fluid. DOT 5 is silicone chemistry .



Fluid Compatibility
Brake system materials must be compatible with the system fluid. Compatibility is determined by chemistry, and no amount of advertising, wishful thinking or rationalizing can change the science of chemical compatibility. Both DOT 3-4 and DOT 5 fluids are compatible with most brake system materials except in the case some silicone rubber external components, such as caliper piston boots, which are attacked by silicon fluids and greases.

Water absorption and corrosion
The big bugaboo with DOT 3-4 fluids always cited by silicone fluid advocates is water absorption. DOT 3-4 glycol based fluids, just like ethylene glycol antifreezes, are readily miscible with water. Long term brake system water content tends to reach a maximum of about 3%, which is readily handled by the corrosion inhibitors in the brake fluid formulation. Since the inhibitors are gradually depleted as. Since the inhibitors are gradually depleted as they do their job, glycol brake fluid, just like anti-freeze, needs to be changed periodically. DOT 5 fluids, not being water miscible, must rely on the silicone (with some corrosion inhibitors) as a barrier film to control corrosion. Water is not absorbed by silicone as in the case of DOT 3-4 fluids, and will remain as a separate globule sinking to the lowest point in the brake system, since it is more dense.

Fluid boiling point
DOT 4 glycol based fluid has a higher boiling point ( 446°F) than DOT 3 ( 446 ºF), and both fluids will exhibit a reduced boiling point as water content increases. DOT 5 in its pure state offers a higher boiling point (500°F) however if water got into the system, and a big globule found its way into a caliper, the water would side at temperatures very much below freezing, let alone at 40° below zero, silicone's low temperature advantage won't be apparent. Neither fluids will reduce stopping distances.

With the advent of ABS systems, the limitations of existing brake fluids have been recognized and the brake fluid manufacturers have been working on formulations with enhanced properties. However, the chosen direction has not been silicone. The only major user of silicone is the US Army. It has recently asked the SAE about a procedure for converting from silicon back to DOT 3-4. If they ever decide to switch, silicone brake fluid will go the way of leaded gas.

Brake system contamination
The single most common brake system failure caused by a contaminant is swelling of the rubber components (piston seals etc.) due to the introduction of petroleum based products (motor oil, power steering fluid, mineral oil etc.) A small amount is enough to do major damage. Flushing with mineral spirits is enough to cause a complete system failure in a short time. I suspect this is what has happened when some car owners changed to DOT 5 (and then assumed that silicone caused the problem). Flushing with alcohol also causes problems. Older brake systems should be flushed only with DOT 3 or 4.

If silicone is introduced into an older brake system, the silicone will latch unto the sludge generated by gradual component deterioration and create a gelatin like goop which will attract more crud and eventually plug up metering orifices or cause pistons to stick. If you have already changed to DOT 5, don't compound your initial mistake and change back. Silicone is very tenacious stuff and you will never get it all out of your system. Just change the fluid regularly. For those who race using silicone fluid, I recommend that you crack the bleed screws before each racing session to insure that there is no water in the calipers.

New developments
Since DOT 4 fluids were developed, it was recognized that borate ester based fluids offered the potential for boiling points beyond the 446°F requirement, thus came the Super DOT 4 fluids - some covered by the DOT 5.1 designation -which exhibit a minimum dry boiling point of 500°F (same as silicone, but different chemistry).

Additionally, a new fluid type based on silicon ester chemistry (not the same as silicon) has been developed that exhibits a minimum dry boiling point of 590°F. It is miscible with DOT 3-4 fluds but has yet to see commercial usage." I learned in the past thru others mistakes not to switch to DOT 5 in systems designed for DOT 3 or 4.