V. hot brake caliper

[Guest ratchethack]

If the brake was locking up for what ever reason. 1,2 or 3, there would be no effect pressing the pedal because the brake is already applied. The question, is did the pedal fade (become spongy) or was it just not responding since it was already applied?

As I mentioned, he experienced "entire loss of rear brake feel repeatedly". By this I meant it went spongy and did not respond (again as mentioned) just moments before locking up.

This makes no sense to me. Rapid cooling? Most of the fluid is in the caliper, I'd think it would stay hot for awhile, that is a bit of metal to cool down. Vacuum sucking the pedal down overcoming the master's internal spring? That's some vacuum. Why again is the relief port closed? Pedal must be depressed or insufficient freeplay in the linkagefor the master's piston to cover the port.

Doesn't entirely make sense to me either, Dan. Yet I saw what I saw (we both did) and this is the best explanation I can think of.

 

It seems reasonable to me that if water in solution in the BF boiled out of the hot caliper (common), it's only pathway is the brake line. With the relief port open, this hot mixture of steam pushing BF would immediately hit relatively cool temperatures in the line. With the brakes being tried repeatedly at intermittent times while this is going on, if the brake lever was depressed with steam in the line, seems more than plausible to me that the lever could have closed the relief port prior to cooling and condensing of the aformentioned BF and steam and/or cooling air in the line, setting up a vacuum. How else might wot we both witnessed be interpreted?

If his brake was sorely neglected, how did it become overfilled?

I don't recall that his brake was overfilled, nor do I b'lieve I suggested it was??

 

Just for further clarification, wot I meant by "his brake had been sorely neglected on all 3 counts [the Big 3]" was this: He purchased the bike used off a dealer showroom floor with (IIRC) something like 8K miles on it. Lacking either a Service manual or Owner's manual, and relying 100% on the dealer for service, he did wot I b'lieve many riders do: His "service discipline" consisted of taking the bike to them occasionally, with instructions to, "do whatever is necessary."

 

Lacking any prior service history, and not maintaining a service schedule of any kind, by the time of the "incident" above, it was not known by anyone when or if the rear brake fluid had EVER been changed -- though "whatever is necessary" had of course been assumed to cover rear brake maintenance. Wot we found is that the fluid was the color of coffee and the caliper was loaded with wot appeared to be something like charcoal briquets. We gave it a Guzzi Clinic that included a thorough cleaning of the caliper with solvent and toothbrushes with pistons partically extended, a caliper-off, nipple up bleeding with new fluid (horrendous bad stuff in various states of matter came out ), new pads, greased the pivot shaft, and adjusted the lever height and stop setting. According to our rider, this brake has had no symptoms of any kind ever since.

 

Wot d'you make of it, Chief??

[Dan M]

As I mentioned, he experienced "entire loss of rear brake feel repeatedly". By this I meant it went spongy and did not respond (again as mentioned) just moments before locking up.

 

Doesn't entirely make sense to me either, Dan. Yet I saw what I saw (we both did) and this is the best explanation I can think of.

 

It seems reasonable to me that if brake fluid boiled out of the hot caliper, it's only pathway is the brake line. With the relief port open, this hot mixture of boiling BF, air and steam would hit relatively cool temperatures in the line. With the brakes being tried at intermittent times, if the brake lever was depressed at the right time, seems plausible to me that the lever could have closed the relief port prior to cooling and condensing of the aformentioned BF and steam and/or cooling air in the line, setting up a vacuum. How else might wot we both witnessed be interpreted?

 

I don't recall that his brake was overfilled, nor do I b'lieve I suggested it was??

 

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.

[Guest ratchethack]

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.

Dan, I'm not asking you to buy anything. I don't believe lots of things I read here and I reckon we all well consider the sources of wot we read here for all the right reasons before placing any degree of credibility or reliance on any of 'em. . . Or if not -- we damned well should!!

 

FWIW, as noted before, the incident above was not the only one I know about. At least one other for all practical purposes identical rear wheel lockup on the road has been reported in the last few years on this Forum. To me it had the ring of authenticity about it, but then I'm not sure I would've felt the same way about it had I not already seen the scenario myself as described above.

[Guest ratchethack]

I did NOT build a heavy brake lever!

 

I can see that I'm going to have to weigh the thing at some stage

BFG, don't knock yourself out, but by all means I'm sure there would be at least a few who'd be interested. [sigh] Per previous posts, I reckon you may have added an ounce or thereabouts with your most Masterful Bodge.

 

As with so many other things in life, wot is or is not significant in terms of weight on a motorcycle always seems to be a matter of proportion and perspective, doesn't it?

 

BAA, TJM, & YMMV

[belfastguzzi]

Hm. Two grams of weight savings at the center of a ~40 lb. wheel/bevel drive hub amounts to a weight savings of one part in 9,072 by my calculation. This is very nearly a fourth order of magnitude weight differential.

I keep my tools in the wheel hubs. Is that not what the hole in the middle is for?

Only problem I have found is sorting out the socket set, 'cause you got to feed them in one by one.

Am I doing something wrong?

[Guest ratchethack]

Am I doing something wrong?

On the contrary -- I b'lieve you may be on to something here, BFG.

 

The woods hereabouts 'r full o' many kinds of "blinged-out" vehicles of every description. Each set of giant chrome wheels with rotating wheel spinners, giant rear wings, flamboyant paint jobs, and coffee-can sized exhaust tips are evident attempts to out-bling the other.

 

Tools in the wheel spokes may well be "The Next Thing in Audio Bling" for Guzzis! I'll bet it makes even more godawful racket than multi-thousand watt subwoofers capable of setting off car alarms from half a block away!

[Dan M]

 

Lacking any prior service history, and not maintaining a service schedule of any kind, by the time of the "incident" above, it was not known by anyone when or if the rear brake fluid had EVER been changed -- though "whatever is necessary" had of course been assumed to cover rear brake maintenance. Wot we found is that the fluid was the color of coffee and the caliper was loaded with wot appeared to be something like charcoal briquets. <_ we gave it a guzzi clinic that included thorough cleaning of the caliper with solvent and toothbrushes pistons partically extended caliper-off nipple up bleeding new fluid bad stuff in various states matter came out src="%7B___base_url___%7D/uploads/emoticons/default_whistle.gif" alt=":whistle:"> ), new pads, greased the pivot shaft, and adjusted the lever height and stop setting. According to our rider, this brake has had no symptoms of any kind ever since.

 

Wot d'you make of it, Chief??

 

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.

[Darius]

Great Gertie's galloping garterstraps, BFG!

 

Looks much like the symptoms I've observed on the road on 2 other V11's -- certainly not me own! Heaven forfend!

 

I posted about rear brake groan and the underlying causes years back, and can't recall the 3 main causes I'd identified (OK, well sure I can: water in fluid, air in fluid, and caked-on brake dust & dirt in the calipers. If you're interested, I think you'll find a fairly comprehensive analysis if you do a search on hygroscopic ). But neglect of proper brake maintenance, including brushing out with solvent between pistons and calipers, combined with the usual neglect of proper bleeding had at one point conspired to make one set of dragging pads I looked at overheat and discolor the disk rather spectacularly, as well as to generate enough water vapor from boiling water in the fluid to cause the brake to first fail, and then lock up, causing the brake lever to drop straight down without resistance, despite an acceptable level in the reservoir.

 

The good news is that it appears that a thorough cleaning, along with new pads and proper bleeding with fresh BF would more'n likely have you back on the road PDQ.

 

Just my opinion, of course. Hope this helps.

 

Who wants to look up any o' my old blather? Well, I did. Here's the short version:

 

For those not prepared for my overly-verbose coverage (no offense taken ), I'd summarized things in two points, which I copy below:

 

1. The V11 rear brake requires special attention exceeding that required by most other motorcycle rear brakes. This is due both to it's high susceptability to accumulation of brake dust and crud, and the fact that it can't be bled properly using bleeding procedures that work just fine with most other motorcycles. The caliper bleed nipple is NOT at the top of the caliper. This means that it's IMPOSSIBLE to get all the air out of this caliper without taking it off the bike. Someone posted a bleeding procedure that calls for leaving the caliper on the bike and pressing the pistons all the way back in their bores to get "virtually" all the air and water out. Now this may just be me, but I'm not happy with "virtually" safe brakes! I find that taking the caliper off isn't much of a chore, (you've got to get it off to get the crud out anyway!), and I'm far more confident knowing with certainty that it's been bled with the bleeder nipple pointing UP, and at least ALL the air is OUT.

 

2. I maintain that because the V11 rear brake is sensitive to conspiratorial attack by "THE BIG THREE" (air and water in the fluid, and accumulated crud between pistons and caliper), it's at the very least UNWISE to rely solely on adding free play at the lever as a "solution". I consider this false insurance. I've demonstrated, at least to my own satisfaction, that no amount of added free play at the lever is atonement enough for neglect of a proper defense against the root causes. Proper bleeding and cleaning knocks THE BIG THREE out of consideration. Since I began doing this with every other rear tire change, I've been confident with next to ZERO free play at the lever - and no symptoms whatsoever -- not one hint of a problem of any kind.

 

There now. Have I finally made a coherent point without stepping on my own foot (- err...brake)?!

 

 

I had as similar event of the rear brake dragging and bringing the bike to a stop followed by the brake hose popping loose at the caliper! Fortunately this occurred just 3 miles form home. I believe this was caused by water in the fluid so I replaced the hose and bleed the system - good to go - sort of...... There was sufficient freeplay in the rear brake lever to allow fluid to come through the reservoir for bleeding. However, when I go for a ride the brake pedal freeplay goies away after a few minutes and starts to drag slightlly. Then the freeplay returns to normal (in about 30 minutes) and is OK for the rest of the ride. What I cannot understand is why pressure in the system does not bleed into the reservoir instead of locking up the system. Is there some sort of check valve in the master cylinder that might be malfunctioning? Any pearls of wisdom would be most appreciated.

[Guest ratchethack]

What I cannot understand is why pressure in the system does not bleed into the reservoir instead of locking up the system. Is there some sort of check valve in the master cylinder that might be malfunctioning? Any pearls of wisdom would be most appreciated.

Darius, if there's any pressure on the brake pedal at all, or if the piston in the master cylinder sticks in its bore, it closes the relief port to the reservoir at the master cylinder, and the pressure in the system can't escape. The symptoms are dragging brake pads. This starts the vicious heat/drag cycle, which had the spectacular results I witnessed and posted elsewhere. You may've been lucky your hose let go. . .

 

Sounds to me like you still have air left in the system. Best have the caliper off the bike with bleed nipple pointing UP, and rap on it while someone helps bleed it. Tilting it at different angles at the same time helps relieve trapped pockets of air. By my experience, this can release relatively huge amounts. Depending on your climate/weather, a new can of brake fluid every time ensures you're not putting "new", yet pre-contaminated fluid in there from exposure to moisture in the air.

[Darius]

Darius, if there's any pressure on the brake pedal at all, or if the master cylinder sticks in its bore, it closes the relief valve to the reservoir at the master cylinder, and the pressure in the system can't escape. The symptoms are dragging brake pads. This starts the vicious heat/drag cycle, which had the spectacular results I witnessed and posted elsewhere. You may've been lucky your hose let go. . .

 

Sounds to me like you still have air left in the system. Best have the caliper off the bike with bleed nipple pointing UP, and rap on it while someone helps bleed it. By my experience, this can release relatively huge amounts of trapped air. Depending on your climate/weather, a new can of brake fluid every time ensures you're not putting pre-contaminated fluid in from moisture in the air.

 

Ratchet - thanks for the reply. I did follow your advise and bleed the caliper off the bracket and held as high as possible - perhaops I will repeat the bleed but based on the firmness in the pedal once it travels about 1.5 inches I am guessing air is not my problem. Perhaps the water in the fluid has corroded the master cylinder piston?? Here again - my puzzlement is, given adequate freeplay at the pedal, would pressure build up not tend to push the piston down eventually clearing the relief valve to the reservoir? I couldn't find a blow-up diagram of the master cylinder innards in the service manual so I am "flying blind" as the saying goes. I am picturing the piston covering the relief hole to the reservoir as it goes through its initial travel. I must be missing something in my thinking here - perhaps a lot!http://www.v11lemans.com/forums/style_emoticons/default/cool.gif

http://www.v11lemans.com/forums/style_emot...efault/cool.gif

[Guest ratchethack]

. . .my puzzlement is, given adequate freeplay at the pedal, would pressure build up not tend to push the piston down eventually clearing the relief valve to the reservoir? . . .

This is the way it's supposed to work and most often does, Darius. Not to confuse things, but per previous posts in this thread, I've personally witnessed, up close and personal, things that at least partially defy explanation -- or at least are beyond my comprehension. Wot is hardly debatable, however, is the fact that brakes that are properly serviced and cleaned, and especially the rear P32B Brembo on V11's, when EXTRA care is given, tend to have little to ZIP problems. I speak from personal experience on this.

. . .I am picturing the piston covering the relief hole to the reservoir as it goes through its initial travel. I must be missing something in my thinking here - perhaps a lot!

I don't think you're missing anything big here. It could hardly be simpler mechanically. Wot's difficult to know is exactly how the slow and steady buildup of underlying causes suddenly result in a relatively rapid sequence of events within the brake system as the dynamics of thermophysics phenomena take over while a panicky rider vigorously pumps a brake that has no braking effect -- sight unseen, as it were. . .

[leafman60]

Based on what Im reading here, Id recommend replacing the master cylinder. It wont hurt and it's not very expensive. I recently encountered a rear pedal that just would not feel right, no matter how much I bled the system. ( u r correct to bleed the caliper off the bracket with bleed fitting pointing up) I replaced the master cylinder and the difference was dramatic.