Rear brake Problem

[bigbikerrick]

The last week or so my rear brake has been "groaning" when I push the bike into the garage. Today I heard a scraping,or grinding sound. I figgured it must need cleaning as stated in the forum.Then I took a good look at the rotor and was surprised that it was scored quite a bit. I removed the caliper and pads and found that the pads were scratching the rotor in areas where the pads have the copper colored metallic particles embedded in the friction material. the pads are the stock ones,and are not worn out, the bike has 7500 miles,and I dont use the rear brake alot. The rotor even had a point in one of the ridges that are scored in it that had a sharp little piece of rotor metal sticking up ,you could feel it as a "snag" with your fingernail. I took it down with a small knife sharpening whetstone,and smoothed it further with 600 grit sandpaper. This has me concerned,are the brake pads too harsh for the rotors? should I change to a different type of pads? or is there some other problem going on here? Im hesitant to ride the bike until I get some advice from the "gurus" on this forum as I dont want to screw up the rotor more. all advice ,and opinions are greatly appreciated.

[Guest ratchethack]

Rick, this is a pretty common thing. There seem to be a couple of things at work here that can be taken care of with a little effort on your part that IMHO have a high degree of probability of eliminating the symptoms.

 

The first thing is the fact that many (IMHO, too many) riders ignore basic brake (and clutch) maintenance and don't bleed them properly. In a dry climate it's not as much of a problem - but the need for it still exists. Brake fluid is powerfully hygroscopic, to the point that it will actually draw humidity from the air into solution right through the plastic of the the brake reservoirs and seals. They should be thoroughly bled IMHO a minimum of once per year with NEW fluid always - not that left-over 5-year old bottle in the corner of your garage! Besides raising havoc with corrosion inside the calipers and pistons, water just keeps accumulating in solution (it can't go anywhere!). When the caliper heats up with application of the brakes, the H2O expands dramatically as water vapor and your brakes go mushy. Keep up the neglect and they'll be heading south altogether... (not likely at a time & place of your choosing)

 

The other thing is that because the caliper is below the swingarm, it tends to retain a lot of brake dust and road crud. This cakes-up and tends to make the pistons hang in the calipers and drag the pads, heating the rotors, pads, and calipers, starting the odious progressive heat/drag cycle. The caliper should be periodically carefully cleaned out with a toothbrush. Leaving the hydraulic line intact, I remove the caliper, take the pads out, hit it with Brakleen, and dunk the whole caliper in a container of Simple Green solution and brush it out. Extending the brake pistons to expose the seals (don't extend 'em too far, or they'll pop out - NOT GOOD) and carefully brushing out the seal grooves will allow removal of all the buildup. I do it with every tire change front & rear.

 

With these 2 items attended to, your backup brake groan should disappear.

 

I have a pal with a LeMans who's rear brake was so badly neglected after only about 10K miles that it sponged-out completely several times on him on long rides and dragged so badly that it overheated and nearly trashed his rotor. Like many others I've heard about and seen personally, he had been treating his symptoms by adjusting more & more play into his brake. This is treating a symptom without any attention to the cause. We gave it a little Guzzi Clinic session. He knows better now.

 

I've renewed mildly-scored rotors on many other bikes with an angle-grinder by spinning the wheel with the spindle clamped in a vise or on a bench, but it's not always easy to get a perfect result, and many rotor carriers won't allow you to reverse the rotor to dress up the other side. Sounds like you did fine with your dress-up, though you ain't gonna make much progress with 600-grit! I'd use something like 150-grit emery paper.

 

The Road Geez "non-racing" choice of pads is Ferodo Platinum or any other standard, non-sintered pad. They won't groove your rotors.

[dlaing]

Good question and Good answer.

I have always been concerned that metallic pads score rotors, but after a quick google, it is heat that causes scoring and NOT metallic pads.

Which matches up with Ratchet's answer.

There used to be alot of comments about rear brake noise when rolling the bike back or forward.

I guess almost everyone has heeded the advice of a proper maintainance regime, as there has not much moaning about groaning

In addition to atleast an annual fluid transplant, I also recommend the technique of frequently wrapping the brake lever shut and let sit over night. I also do the same with the rear lever, but it is trickier. I stick a crutch under the footpeg, over the brake lever, and wedge it against the bike. It is a bit of a balancing act. I suppose a 5KG barbell on a rope would be better.

And it cannot be expressed often enough that the rear pad can wear very quickly, so it should be checked frequently.

Also, always be sure to check and double check the routing of the rear brake line after rear tire changes, as some wrenches are negligent.

And it cannot be reiterated enough that one should change your fluid frequently, like what Ratchet said.

Oh, and setting a little freeplay at the rear lever, is debatably a good safety measure. (don't ask why it is debatably, just read this thread

http://www.v11lemans.com/forums/index.php?showtopic=5071&hl= )

[O2 V11]

It appears the wear on Rick's rear disc is similar to mine. I have done 6000 miles and are not a heavy user of the brakes. It is a worry that my disc is wearing as well. I would not have expected any wear in the rotor at all with factory pads. If they were sintered HH replacements, one could expect some wear in the rotor. Even one of the front rotors is wearing slightly. I noticed the wear pattern on ckamin's rear rotor in his recent pics of his porkchop. His rotor is identical to mine in appearance. Is anyone else experiencing wear in their rotors at such a low mileage as we are?

Rob

[bigbikerrick]

Rick, this is a pretty common thing.  There seem to be a couple of things at work here that can be taken care of with a little effort on your part that IMHO have a high degree of probability of eliminating the symptoms. 

 

The first thing is the fact that many (IMHO, too many) riders ignore basic brake (and clutch) maintenance and don't bleed them properly.  In a dry climate it's not as much of a problem - but the need for it still exists.  Brake fluid is powerfully hygroscopic, to the point that it will actually draw humidity from the air into solution right through the plastic of the the brake reservoirs and seals.  They should be thoroughly bled IMHO a minimum of once per year with NEW fluid always - not that left-over 5-year old bottle in the corner of your garage!  <_ besides raising havoc with corrosion inside the calipers and pistons water just keeps accumulating in solution can go anywhere when caliper heats up application of brakes h2o expands dramatically as vapor your mushy. keep neglect they be heading south altogether... src="%7B___base_url___%7D/uploads/emoticons/default_ohmy.png" alt=":o">

 

The other thing is that because the caliper is below the swingarm, it tends to retain a lot of brake dust and road crud.  This cakes-up and tends to make the pistons hang in the calipers and drag the pads, heating the rotors beyond what they can take.  The caliper should be periodically carefully cleaned out with a toothbrush.  I hit it with Brakleen and dunk the whole caliper in a container of Simple Green solution to brush it out.  Extending the brake pistons to expose the seals (don't extend 'em too far, or they'll pop out - NOT GOOD) and carefully brushing out the seal grooves will allow removal of all the buildup.  I do it with every tire change front & rear.

 

With these 2 items attended to, your backup brake groan should disappear.

 

I have a pal with a LeMans who's rear brake was so badly neglected after only about 10K miles that it sponged-out completely several times on him on long rides and dragged so badly that it overheated and nearly trashed his rotor.  Like many others I've heard about and seen personally, he had been treating his symptoms by adjusting more & more play into his brake.  This is treating a symptom without any attention to the cause.  We gave it a little Guzzi Clinic session.  He knows better now.  

 

I've renewed mildly-scored rotors on many other bikes with an angle-grinder by spinning the wheel with the spindle clamped in a vise or on a bench, but it's not always easy to get a perfectly flat result.  Sounds like you did fine with your dress-up, though you ain't gonna make much progress with 600-grit!  I'd use something like 150-grit emery paper.

 

The Road Geez "non-racing" choice of pads is Ferodo Platinum or any other standard, non-sintered pad.  They won't groove your rotors.

73902[/snapback]

Thanks for the prompt reply Ratchet, I removed the pads from the caliper last night and sprayed aerosol brake cleaner on the caliper and piston area and wiped it down with a rag. I think I need to do the more detailed cleaning you recommend. a couple of questions...... how do you partially extend the pistons out from the caliper without going too far? Do yoy remove the caliper from the brake hose to do this maintenance,or leave it attatched? ( I cleaned mine with the caliper still attatched) also where do you recommend I purchase the "road geeze" pads? I think they will be ok for me as I mostly brake with the front brake. lastly... do you use the pushrod threaded adjustment on the rear master cylinder to set the freplay? how do you know when the freeplay is enough, or if its already enough. Pardon my ignorance, but I really dig this Guzzi and want to make sure everything is just right.

[bigbikerrick]

It appears the wear on Rick's rear disc is similar to mine. I have done 6000 miles and are not a heavy user of the brakes. It is a worry that my disc is wearing as well. I would not have expected any wear in the rotor at all with factory pads. If they were sintered HH replacements, one could expect some wear in the rotor. Even one of the front rotors is wearing slightly. I noticed the wear pattern on ckamin's rear rotor in his recent pics of his porkchop. His rotor is identical to mine in appearance. Is anyone else experiencing wear in their rotors at such a low mileage as we are?

Rob

73914[/snapback]

Ya know, Rob this rear disc wear reminds me of a98 suzuki intruder 1500 LC I used to have, those bikes were heavier than heck ,and had a smallish rear brake that would wear the crap out of the rotor and the pads, actually it was a chronic brake drag problem caused by heat that would expand the pistons and they would bind up in their bores. I had to change the oil and rear pads every 3K miles! needless to say I got rid of that POS Suzuki ,and replaced it with the 2000 Kawi nomad I now have for touring duty.

[bigbikerrick]

Good question and Good answer.

I have always been concerned that metallic pads score rotors, but after a quick google, it is heat that causes scoring and NOT metallic pads.

Which matches up with Ratchet's answer.

There used to be alot of comments about rear brake noise when rolling the bike back or forward.

I guess almost everyone has heeded the advice of a proper maintainance regime, as there has not much moaning about groaning 

In addition to atleast an annual fluid transplant, I also recommend the technique of frequently wrapping the brake lever shut and let sit over night. I also do the same with the rear lever, but it is trickier. I stick a crutch under the footpeg, over the brake lever, and wedge it against the bike. It is a bit of a balancing act. I suppose a 5KG barbell on a rope would be better.

And it cannot be expressed often enough that the rear pad can wear very quickly, so it should be checked frequently.

Also, always be sure to check and double check the routing of the rear brake line after rear tire changes, as some wrenches are negligent.

And it cannot be reiterated enough that one should change your fluid frequently, like what Ratchet said.

Oh, and setting a little freeplay at the rear lever, is debatably a good safety measure. (don't ask why it is debatably, just read this thread

http://www.v11lemans.com/forums/index.php?showtopic=5071&hl=  )

73904[/snapback]

Thanks for the post and informative link, Dlaing. Im going to service the caliper,and bleed the brake with fluid from a brand new container in the morning.

[bigbikerrick]

Rick, this is a pretty common thing.  There seem to be a couple of things at work here that can be taken care of with a little effort on your part that IMHO have a high degree of probability of eliminating the symptoms. 

 

The first thing is the fact that many (IMHO, too many) riders ignore basic brake (and clutch) maintenance and don't bleed them properly.  In a dry climate it's not as much of a problem - but the need for it still exists.  Brake fluid is powerfully hygroscopic, to the point that it will actually draw humidity from the air into solution right through the plastic of the the brake reservoirs and seals.  They should be thoroughly bled IMHO a minimum of once per year with NEW fluid always - not that left-over 5-year old bottle in the corner of your garage!  <_ besides raising havoc with corrosion inside the calipers and pistons water just keeps accumulating in solution can go anywhere when caliper heats up application of brakes h2o expands dramatically as vapor your mushy. keep neglect they be heading south altogether... src="%7B___base_url___%7D/uploads/emoticons/default_ohmy.png" alt=":o">

 

The other thing is that because the caliper is below the swingarm, it tends to retain a lot of brake dust and road crud.  This cakes-up and tends to make the pistons hang in the calipers and drag the pads, heating the rotors beyond what they can take.  The caliper should be periodically carefully cleaned out with a toothbrush.  I hit it with Brakleen and dunk the whole caliper in a container of Simple Green solution to brush it out.  Extending the brake pistons to expose the seals (don't extend 'em too far, or they'll pop out - NOT GOOD) and carefully brushing out the seal grooves will allow removal of all the buildup.  I do it with every tire change front & rear.

 

With these 2 items attended to, your backup brake groan should disappear.

 

I have a pal with a LeMans who's rear brake was so badly neglected after only about 10K miles that it sponged-out completely several times on him on long rides and dragged so badly that it overheated and nearly trashed his rotor.  Like many others I've heard about and seen personally, he had been treating his symptoms by adjusting more & more play into his brake.  This is treating a symptom without any attention to the cause.  We gave it a little Guzzi Clinic session.  He knows better now.  

 

I've renewed mildly-scored rotors on many other bikes with an angle-grinder by spinning the wheel with the spindle clamped in a vise or on a bench, but it's not always easy to get a perfectly flat result.  Sounds like you did fine with your dress-up, though you ain't gonna make much progress with 600-grit!  I'd use something like 150-grit emery paper.

 

The Road Geez "non-racing" choice of pads is Ferodo Platinum or any other standard, non-sintered pad.  They won't groove your rotors.

73902[/snapback]

Sorry Ratchet, but another question occured to me... Is there a difference between the two pads in the rear ( inner and outer pad),or are they interchangeable? Muchas Gracias, mi Compadre, Muy Amable.

[Guest ratchethack]

Thanks for the prompt reply Ratchet, I removed the pads from the caliper last night and sprayed aerosol brake cleaner on the caliper and piston area and wiped it down with a rag. I think I need to do the more detailed cleaning you recommend. a couple of questions...... how do you partially extend the pistons out from the caliper without going too far? Do yoy remove the caliper from the brake hose to do this maintenance,or leave it attatched? ( I cleaned mine with the caliper still attatched) also where do you recommend I purchase the "road geeze" pads? I think they will be ok for me as I mostly brake with the front brake. lastly... do you use the pushrod threaded adjustment on the rear master cylinder to set the freplay? how do you know when the freeplay is enough, or if its already enough. Pardon my ignorance, but I really dig this Guzzi and want to make sure everything is just right. 

73915[/snapback]

Rick, I think many of your questions are answered in the link that Dave provided above. I've gotta post quickly and pick this up later if necessary.

 

OK, now it's time for a little mea culpa . Dave, I had been searching for the thread you linked in post #3 above, but couldn't find it. Thanks for posting it. There's some good stuff there in the little debate we had.

 

Now here's where I "come clean". After this debate, I went to a clinical laboratory liquidator and bought a couple of flasks, pipettes, and small stuff and disappeared into the "laboratory" with an industrial thermometer with the intention of accurately graphing out and calculating the CoE of brake fluid. What happened was unexpected:

 

1. It was clear that brake fluid DOES in fact expand with heat.

 

2. My industrial thermometer only worked within a tiny operating range before it froze up. It's apparently junk now, and I never found a replacement, so I couldn't proceed with my study.

 

So PETE WAS RIGHT, and I WAS APPARENTLY WRONG (wot? - no surprise?! ) about the CoE of brake fluid, but I STILL have no way to quantify it. From what I was able to observe, it isn't LARGE, but it isn't as infinitessimally small as I had suspected, either.

 

Pete's points about the operation of the relief port are important to understand. Clearly, if you rest your foot at all on the brake lever, you're just begging for trouble. No getting around Pete's point there. You stand a better chance of keeping that relief port open with a few mm of free play than with less. He also said that the CoE of BF is irrelevant, and I've come to agree. As long as the relief port is functioning and stays operational after the most strenuous heat cycle of one braking application, the CoE is for the most part moot.

 

Now - I've been riding probably 10K miles with next to ZERO free play in my brake lever with NO brake dragging and NO other kinds of symptoms. Is this significant? Maybe, maybe not, depending on the attention a rider pays to overall brake system condition, adjustment, and riding habits. I know many guys who don't have a clue how much play they have in their rear brake, and don't care, since they "don't use it very much." Well, neither do I, relative to the fronts, but I always pay pretty close attention to my brakes and keep them in good operating order. I reckon if you aren't sure about the accumulation of the BIG THREE in your brakes (air, water, and caked-on crud 'twixt the pistons and calipers - see link Dave posted above) you oughta have a few mm of free play as Pete suggested. Me, I'm pretty sure. Since I ride with the balls of my feet on the pegs, I've eliminated one of the foremost (IMHO) potential initiators of the heat/drag cycle (riding with the relief port closed from unintentional pressure on the brake lever). I'll continue to do what I've been doing (tight, to the point of ZERO free play) and keep a close eye on it. IMHO, it has much superior feel this way, y'see, and therefore I get better control...

 

Dave - I can't imagine how heat in and of itself could score rotors? All brakes function by converting kinetic enerty into thermal energy. Not all rotors get scored....

 

Rick - the pads are identical, but once you use them, they take on a directional wear pattern and they should always be re-installed the same way they came out.

[jrt]

One small addition- inspect your rear brake rotor for discoloring (blueing) which indicates heat, presumably due to brake drag.

 

 

Edit: I'm not sure how much this will help you Ratchet, but I looked up the cubical expansion of liquids in my CRC handbook:

 

V(T) = V0*(1+aT + bT^2+gT^3)

liquid, T(range), aX10^3, bX10^6, gX10^8, "true coeffecient" (not sure what this is...)

 

Aw, shoot- I'll just scan and post it. Lemme see if I can find a more recent data set also. Back in an hour. Anyone know what time it is?

[bigbikerrick]

Rick, I think many of your questions are answered in the link that Dave provided above.  I've gotta post quickly and pick this up later if necessary.

 

OK, now it's time for a little mea culpa on my part.  Dave, I had been searching for the thread you linked in post #3 above, but couldn't find it.  Thanks for posting it.  There's some good stuff there in the little debate we had. 

 

Now here's where I "come clean".  After this debate, I went to a clinical laboratory liquidator and bought a couple of flasks, pipettes, and small stuff and disappeared into the "laboratory" with an industrial thermometer for the purpose of accurately graphing out the CoE of brake fluid.  What happened was unexpected:

 

1.  It was clear that brake fluid DOES in fact expand with heat.  

 

2.  My industrial thermometer only worked within a tiny operating range before it froze up.  It's apparently junk now, and I never found a replacement, so I couldn't proceed with my study. <_>

 

So PETE WAS RIGHT, and I WAS APPARENTLY WRONG (what - no surprise?! ) about the CoE of brake fluid, but I STILL have no way to quantify it.  From what I was able to observe, it isn't LARGE, but it isn't as infinitessimally small as I had suspected, either.

 

Pete's points about the operation of the relief port are important to understand.  Clearly, if you rest your foot at all on the brake lever, you're just begging for trouble.

 

Now - I've been riding probably 10K miles with next to ZERO free play in my brake lever with NO brake dragging and NO other kinds of problems.  Is this significant?  Maybe, maybe not, depending on the attention a rider pays to overall brake system condition and adjustment.  I know many guys who don't even know how much play they have in their rear brake, and don't care, since they "don't use it very much."  Well, neither do I, relative to the fronts, but I always pay pretty close attention to my brakes and keep them in good operating order.  I reckon if you aren't sure about the content of the BIG THREE in your brake fluid (see link Dave posted above) you oughta have a few mm of free play as Pete suggested.  Me, I reckon I'll do what I've been doing and continue to keep a close eye on it.

 

Dave - I can't imagine how heat in and of itself can score rotors?

 

Rick - the pads are identical, but once you use them, they take on a directional wear pattern and they should always be re-installed the same way they came out.

73945[/snapback]

Thanks for the information, Senor Ratchet. I swapped the pads thinking it would be better to "rotate" them to equalize wear, as one was a little more worn than the other.... Me Bad! Im going to swap them back today when I do the detailed rear brake caliper cleaning "a la Ratchet".

[jrt]

Of course this doesn't have brake fluid, but glycerine, petroleum, or kerosene might be good approximations...or at least give you an idea of the upper end.

Now...

What's the dead volume of a brake slave cylinder?

[Guest ratchethack]

Of course this doesn't have brake fluid, but glycerine, petroleum, or kerosene might be good approximations...or at least give you an idea of the upper end. 

Now...

What's the dead volume of a brake slave cylinder?

73955[/snapback]

Jason, this is the kind of chart I kept running into on my unsuccessful search of many Automotive Engineering & Petrochem sites looking for the CoE of brake fluid. As it happens in Physical Chemistry, you can't take the CoE of a "similar" material, even one with many identical chemical components, and make any assumptions whatsoever about approximating the CoE of another material. Again, the properties of brake fluid are tightly controlled by design. In my reading, I started to come around to the idea that since the CoE of BF is conspicuously absent from all the property data sheets, that it must not be very important to anybody...and therefore, it isn't significant enough for our purposes to have much concern over - but this doesn't take away from the importance of bleeding brakes & keepin' the stuff fresh, IMHO!

 

BAA, TJM & YMMV

[jrt]

I imagine it is not published because it is a 'trade secret' rather than not being interesting.

While you cannot use a compound to get an accurate estimation of brake fluid, at least this will put you at the upper limit of expansion. I was looking for silicone oils as well, since they are used in some brake fluids, but I haven't found them yet.

edit: apparently, borate esters are used as well. I quote the following from "Bulletin of the National Research Centre, Egypt"

 

Hydraulic fluid compns., prepd. according to DOT 4 and SAE std. specifications, consisted of 25-70 wt.% borate esters of "hydroxyethyl amine" (i.e., diethanolamine), 27-73 wt.% diluent, and additives. The borate ester was a product of the reaction of boric acid, glycol, alkoxyethoxy ethanols (e.g., methoxy ethoxy and/or butoxy) and diethanolamine. To insure suitable viscosity and b.p., to reduce the amt. of additive used and at the same time to attain suitable anticorrosion properties, the diethanolamine was incorporated into the boric acid glycol ester complex. The performance requirements and tests described for brake fluid in the Stds. Specifications SAE, DOT 3, and DOT 4 were tested by measuring their equil. reflux b.p. (dry and wet), viscosity, pour point, pH, fluidity at low temp., high-temp. stability, corrosion, evapn. loss, water tolerance, flash point, and effect on rubber. The exptl. data of the formulated fluids were treated math. Hydraulic brake fluid matching nearly all the current stds. can be achieved by using some of the prepd. fluid compns.

[jrt]

Hey, it's cutting me off.

I gotta go (wife's calling), but here is the rest of what I found:

 

Check here (a patent, so it should be freely downloadable:

 

ibliographic Information

 

Brake fluid. Doelling, George L. (Wagner Electric Corp.). (1950), US 2507401 19500509 Patent language unavailable. CAN 44:36560 AN 1950:36560 CAPLUS

 

Patent Family Information

 

Patent No. Kind Date Application No. Date

US 2507401 19500509 US

 

 

 

Abstract

 

A brake fluid consists of a lubricant selected from the group consisting of the mono- and diricinoleates of the aliphatic glycols having the formula HOCnH2nOH, in which n is an integer from 2 to 4, inclusive, 10-25% by vol.; an aliphatic glycol having the formula HOCnH2nOH, in which n is an integer from 2 to 4, inclusive, 3-15%; 2-methyl-2,4-pentanediol (I), 10-24%; a diluent selected from the group consisting of Pr alcs., Bu alcs., Am alcs., methoxymethoxyethanol, and the lower monoalkyl ethers of ethylene glycol, diethylene glycol, propylene glycol, and dipropylene glycol, 45-70%; and a small but effective amt. of a corrosion inhibitor. Suitable corrosion inhibitors include K, Na, or other alkali-metal salts of castor oil or other fatty acids, nitrites, borates, and other buffer materials. The amt. of inhibitor is preferably 0.2 to about 3.0% of the finished fluid by wt. An example of a fluid consists of propylene glycol (II) mono-ricinoleate about 17% by vol., II about 6, I about 15, and iso-BuOH about 62. About 1.9 g. K ricinoleate is added per 100 cc. of the fluid as corrosion inhibitor.

 

Indexing -- Section 13 (Chemical Industry and Miscellaneous Industrial Products)