Front brake lockups

[brettbolt]

The front brakes on my '06 have locked up twice in the last 6 months.

First time was in September. Before it happened I noticed that the brake lever had very little travel. So I changed the brake fluid and took it to a slow residential street to test. After several uses the brake got tight. Then I noticed I was using a lot of throttle just to keep the bike moving. I let off the throttle and the front wheel locked completely. I went down hard and was bruised badly

After that I replaced the front brake calipers. I thought that fixed it until last Friday. I noticed the same thing -- had to give it a lot of throttle to keep her moving. I let off slightly and the next thing I knew I was tumbling down the road. Fortunately the car behind me stopped in time. Road rash on all 4 limbs. Had to remove the front pads to ride her home, bleeding.

So I ordered a new front brake master cylinder and a bunch of other parts damaged in the crashes. Haven't got the parts yet.

My question is, what can I do to make sure it's fixed right this time? Any help or advice appreciated.

 

[MadBlackGen1]

My guess would be that the master cylinder return bleed hole was clogged. That would prevent fluid from returning to the master after the lever is pressed, pressurizing the brakes and never letting them relax...

I hope your new master cylinder eliminates the problems. And good to hear you're not beat up too bad with two crashes.

 

[sdt354]

I'm glad you weren't injured worse. Make sure you have enough play in the lever to get full release of the brakes after replacing the master. I'd upgrade to stainless brake lines while your working on the brakes. I like HH pads up front. I think the rear will get a set next change. Not related, but I've been using DOT 5 in the back as an experiment for 3 years now. So, the front is getting it too. The fluids can't be mixed in any amounts. A through flushing must come first. Probably best when using all new parts.

 

[Fire-medic]

The hoses could be collapsing internally, too. Replacement is the only way to solve that, if it's the issue. I would replace them w/stainless covered lines, and as recommended, the HH rated pads.

What color is your brake fluid? If it's black and not transparent, you're overdue for a complete flush.

 

[Fire-medic]

I think you're right about the incompatibility of the DOT 5 with DOT 3 or DOT 4, but I believe the DOT 5.1 is compatible with DOT 3 or DOT 4.

Some info:
http://www.stoptech.com/technical-support/technical-white-papers/brake-fluid

A handy chart to know which are compatible:
http://www.epicbleedsolutions.com/resources/faq/difference-between-dot4-and-dot51-brake-fluid/

I'm glad you weren't injured worse. Make sure you have enough play in the lever to get full release of the brakes after replacing the master. I'd upgrade to stainless brake lines while your working on the brakes. I like HH pads up front. I think the rear will get a set next change. Not related, but I've been using DOT 5 in the back as an experiment for 3 years now. So, the front is getting it too. The fluids can't be mixed in any amounts. A through flushing must come first. Probably best when using all new parts.

 

[sdt354]

I think you're right about the incompatibility of the DOT 5 with DOT 3 or DOT 4, but I believe the DOT 5.1 is compatible with DOT 3 or DOT 4.

Some info:
http://www.stoptech.com/technical-support/technical-white-papers/brake-fluid

A handy chart to know which are compatible:
http://www.epicbleedsolutions.com/resources/faq/difference-between-dot4-and-dot51-brake-fluid/

Good info F.M. as usual. I'm using 5.0. Glycol base fluid is good paint remover and will do a number on powder coat also. That's my main reason for going through the trouble of using silicon base fluid. As a side benefit, 5.0 should stay cleaner longer, as it's much less hydroscopic if at all.

 

[brettbolt]

The new master cylinder arrived today. Now I'm wondering if I should get new brake lines -- not sure how to test them? They're the originals (12 years old).

Also, is there a way to know for sure that the brakes won't fail again without doing a road test?

 

[rebeltaz83]

The new master cylinder arrived today. Now I'm wondering if I should get new brake lines -- not sure how to test them? They're the originals (12 years old).

Also, is there a way to know for sure that the brakes won't fail again without doing a road test?

Samething happend to me with my dad's goldwing, only I was in wet grass, trying to start out, brake line was collapsing internally, spun the rear tire right out from under me, bike went down, took my leg with it. I would pump the brakes allot, put it on the center stand, have somebody hold the bike on the rear tire, front wheel should rotate by hand, if it doesn't, loosen the bleeder on each caliper if fluid comes out under pressure, and the wheel turns again, I'd change all three brake lines. Anyways, I got the goldwing to go after I cracked the bleeders and released the pressure off the front brakes. But it would be allot cleaner just to go ahead and change the lines while your putting on the new master. Be sure to clean up any brake fluid, it's a very good paint stripper. Good luck, glad your not badly hurt from going down. Could have been allot worse.

 

[brettbolt]

Good advice -- to be safe I ordered the 3 new brake lines. The bike has sat outside on very hot summer days, which could have deteriorated the rubber.

 

[one2dmax]

The only times I have seen this was:
1) - Someone installed aftermarket levers which didn't fully release the brakes. The continued riding caused excessive heat which in turn caused the fluid to expand (which it does as it heats up) and that caused the lock up.
2) - Over Filling of the reservoir. The condition above would have been mitigated had the fluid level been set to allow for the expansion. This is why your "maximum" limit is lower then the total capacity of the reservoir. In other words. Don't over fill the fluid level. It doesn't have to be all the way to the top.
3) - Failed Brake Lines which caused a one way pressure build situation. This is not very common but can happen. Usually it is due to either a very old set of lines (yours aren't anywhere near that old) OR damage to the lines. Damage to the lines can occur by letting the caliper "hang" unsupported by the line (not really too much of a problem on these bikes but it can contribute). Also damage to the line can be caused by a crimp or kink that could have occurred. Again, the OEM lines are very durable and last for decades without degradation.
4) - Fluid incompatibility. Mixing Dot 5 with any other fluid causes the rubber to degrade and swell (as does carb cleaner by the way).
5) - plugged relief in the master. This is the tiny hole in the master. Usually this isn't a problem unless it's been sitting for a very long time or had a chance to get debris into the reservoir.
6) - Sticking brake caliper piston. Not as common either but can happen. The piston doesn't properly retract when releasing the brake lever. This keeps the pads in contact with the rotor and causes the system to heat up and keep putting more and more pressure on the brakes.

What does the rotor look like? Is it discolored where it maybe has gotten very hot?

 

[brettbolt]

Thanks for the list of possible causes. It could only be #3,#5, or #6.

When I replaced the caliper one of the pistons seemed like it was sticking. After replacing the caliper I was virtually positive I had fixed it, but was proven wrong. My bike only has 6K miles and it has sat a long time unused. So maybe the cause is both #5 and #6? Will find out when I replace the lines and master cylinder next week.

 

[Fire-medic]

If you disassemble the calipers, and clean-up the pistons, you will probably find your issues w/the sticking caliper will be over. You have to do a very thorough job on the removal of any oxidation. If the pistons or the caliper bore have any pitting on the mating surfaces, replace them. Don't forget to clean the square recess for the piston seal in the caliper. I find that a Dremel tool & a brass bristle flat wheel brush does a good job, w/o removing aluminum, like a steel brush might. Service the entire caliper, not just the side that's sticking, of course. And if you do one caliper, you might as-well do both fronts, and probably the rear as-well.

It should be pretty-obvious if a piston is sticking, as the brake actuation won't allow the piston to move. I have done the following for removing a stuck piston. Since you have to disassemble the thing anyway, the method won't hurt anything, just be sure that you do a thorough cleaning of the brake fluid passageways, too.

The time-honored method for removing a stuck piston is to place a wood block between the pistons, where the pistons will not pop-out of their bores, you just want to be able to free-up the stuck one(s). I usually do this with the caliper disconnected from the hoses.Then use a rubber-tipped air supply fixture to fill the caliper w/compressed air (bleeder nipple removed, the tapered rubber tip of the air hose chuck inserted directly into the threaded bleeder nipple hole), and the stuck piston should in most cases pop-free. Of course the other pistons which aren't stuck will also be moving until they contact the piece of wood, that's why you need a piece of wood that will be roughly-equal to the rotor thickness, to prevent the freely-moving pistons from shooting out of their bores. I suggest emptying the caliper first, because if you don't there will be brake fluid spraying everywhere, and you will maybe lose that Conan the Barbarian scene on your gas tank, due-to the corrosive glycol-based brake fluid.

If compressed air will not budge the stuck piston, use a grease gun directly on the bleeder nipple (which should be opened, of-course). Pump the caliper full of grease, and that stuck piston should pop-right-out. I've never been defeated when I had to get to this point. Your average grease gun provides probably fifteen-times the pressure of your air compressor. You just have to be sure that you do a thorough cleaning of the caliper doing it this way, which for me, means disassembling the caliper halves, unless they're monobloc, in which-case they don't come apart.

An alternative method is to use a plumbing tool which is used to remove stuck galvanized pipe from one-another. It's a toothed-cam which inserts into the open piece of pipe, and then uses a wrench to grip the insides of the pipe, via the toothed-cam. Once you break-loose the stuck piston, the air pressure should blow it out of the bore. Home Depot sells a set, called an internal pipe wrench set. Depending on the size of your piston hollow diameter, you may need to order one online or get it from a local plumbing supply house.

 

[93max]

Good info above ^^^^ OR he could go here and get his calipers!
http://vmaxforum.net/showthread.php?t=45899

 

[brettbolt]

Yesterday I finished installing the new brake lines and master cylinder. Today I took a very close look at the old master cylinder. Sure enough, as many have mentioned earlier, the return hole was clogged. (First photo below).

So I took a small needle and cleaned it out. A tiny amber colored crystal came out (shown in the second photo below).

My mistake was that I never changed the brake fluid in the 12 years that I have owned the bike. Over the years, moisture got in and allowed some crystals to form. I feel like a stupid idiot for neglecting the brakes for so long.

Lessons learned (the hard and painful way!):
1) I should have changed the brake fluid every year or two.
2) At the first sign of the brake lever getting harder to pull I should have inspected the master cylinder.

After the second fall I had to promise my wife that I would sell the bike. She said "It's either the bike or me". I will really miss the bike! I will be putting it up for sale with a completely new front brake system. I am also going to inspect the rear brake system and change the fluid.

I hope this highlights the importance of changing the brake fluid regularly!

This is the plugged return hole before I cleared it:

This is after clearing the return hole and shows the crystal that was plugging it:

 

[Fire-medic]

A sad day when you have to choose between the bike and the wife. Unless you're already headed for divorce, there really is no choice there.

I can see her point, the bike's caused you to fall, twice, and you're fortunate it wasn't worse. Some inattentive texting driver could have killed you. And, because you fell in-front of them, they probably wouldn't even have been charged with anything, even-though they were "impaired" because they were posting to instagram their cat's cute picture, instead of paying-attention to what's happening on the road around them.

Any chance the wife would reconsider, since you fixed the issue? Or are you done with motorcycles, forever?

 

[brettbolt]

She is adamant that I sell it, especially after my second brake lockup.

I love riding (have been since 1974), but looking at the tiny fluid return hole in the master cylinder, and knowing that any small particle could clog it scares me.

I always thought if I had an accident it would be caused by an inattentive driver like you said, Fire-medic. If I continued riding I would always be in fear of brake failure or some other unexpected problem, and that seals the deal for me. I realize that it is completely my fault due to lack of maintenance, and after replacing the brake system it would probably never happen again.

Anyway, I can look back and smile at the 12 years of fun I had with my '06 VMax. I still have my 2013 Corvette Grand Sport!

 

[Fire-medic]

Sounds like you're ready to give up riding, glad you got the brakes fixed. Who knows, maybe some-other time.

She is adamant that I sell it, especially after my second brake lockup.

I love riding (have been since 1974), but looking at the tiny fluid return hole in the master cylinder, and knowing that any small particle could clog it scares me.

I always thought if I had an accident it would be caused by an inattentive driver like you said, Fire-medic. If I continued riding I would always be in fear of brake failure or some other unexpected problem, and that seals the deal for me. I realize that it is completely my fault due to lack of maintenance, and after replacing the brake system it would probably never happen again.

Anyway, I can look back and smile at the 12 years of fun I had with my '06 VMax. I still have my 2013 Corvette Grand Sport!

 

[brettbolt]

So.... A month+ later after completely replacing the front brake system I finally built up the courage to take her for a test ride. I have to make sure its safe before I sell it. I wore an armored riding coat, thick gloves, full helmet, etc. Started off slowly on nearby residential streets. Stopped frequently, got off the bike and felt the calipers for excessive heat. And while riding I periodically let off the throttle and pulled in the clutch to make sure there was little or no rolling resistance (any significant resistance would be a sign of trouble).


It was smooth sailing. She checked out OK after 10+ miles. But the front brake was spongy and I suspect there are air bubbles in the system.


I used a vacuum pump on the bleeder valves and cycled lots of fluid through them, while keeping the reservoir filled.



Is there a trick to getting out that last bit of trapped air? I don't bleed brakes very often and any suggestions would be appreciated.

 

[Fire-medic]

The reverse-bleeding method is what I use to remove residual air. You push brake fluid from the brake caliper bleeder upwards. This causes any trapped air to move with the fluid. What is the basic physics of air in liquid? Air is lighter, it rises, correct? Now, add movement of fluid to the air natural tendency, and you see how using a syringe to introduce brake fluid at the caliper bleeders, will remove any residual air pockets.

When you're sitting in-front of your glass of beer, watch what the carbonation bubbles do. Do they sink, or do they rise? Same thing in your brake fluid, and pushing fluid from the lowest access point in the hydraulic system will flush-out any trapped bubbles, giving you a firm lever feel quickly.

The article here will detail the process for reverse-bleeding. This is the fastest, most-effective method, using the least-costly equipment, to remove air from your brakes, or your clutch on a VMax.

http://www.vmaxforum.net/showthread.php?t=45011&highlight=reverse-bleed

Any hydraulic system for brakes or a clutch will last longer without needing work if you change the fluid frequently. That amber crystal of deposits is probably made-of contaminants that got past the brake seals, combined with water, and deterioration of the rubber lines internally, all combining to make a paste that hardened into the nugget of debris which then migrated to the 'choke point' of the smallest passageway in your system, that small pressure-equalization hole that is closest-to the master cylinder banjo bolt. If your brake fluid is opaque, you're way-overdue to change it. If you can see little eddies of what appears to be dark contaminants coming-out of the master cylinder holes when you squeeze the brake lever (be careful, as the brake fluid can squirt a considerable distance!) and swirling around like creamer in your coffee, time to change the brake fluid.

 

[brettbolt]

Thanks, great article about reverse bleeding. Makes perfect sense because trapped air goes upward faster than fluid going down. Will get a pump or syringe and give it a try.