Brake Meltdown!

[Guest dkgross]

so..there I am...heading out for my July 4 run...About 10 miles from home...and I'm noticing the bike bogging down. And smelling weird....My wife pulls up next to me on her bike, holding her nose, and pointing at my back wheel.

 

By the time I hit the off ramp (another 1/4 mile), The revs are dropping, and the smell is dreadful. I go to hit the brakes, and the back wheel locks. Luckily the fronts are working.

 

As I get off the bike, I look at the back wheel, and the brake rotor is GLOWING red. There's smoke coming from the calipers, and a thick, black gooooo dripping from within.

 

I think my ride for the day is over

 

 

I called the AMA Motow insurance folks and they send a truck (rather quickly, I might add). The tow dude was VERY careful and VERY good at securing the bike safely. We drove to Moto International (and of course, they're closed until Tuesday because of the holiday).

 

As fate and karma would have it, Micha just happens to pull up on his scooter to pick his van up!!! I told him what happened, and he says "yeah..I've seen this before". He didn't seem to want to elaborate, and I didn't ask. I was just thrilled that he was able to lock the bike up inside for me!!!. And, he even offered to let me take a cruiser home for the weekend!! (I declinded...it's an insurance thing..) But it was damned nice of him to ask.

 

so...we'll see what tuesday brings...

 

[dlaing]

Glad you have an angel riding shotgun!

You may have missed this post:

Brake Drag Thread posted by John O'Sullivan

 

Following the advice of that post, I adusted my brakes last weekend.

(I am hoping to get better gas mileage now (dreaming))

I am not sure at what point the piston starts to engage, but assuming that it is at the end of the spring travel, I gave it about five millimeter more travel measured where you press your foot. I guess the pedal will bounce up and down a bit now, but atleast there is room for some fluid expansion without the brake pedal rising into the stop and causing more drag, more heat, boiled fluid, locked brake, and sudden death.

I tried a couple of stops from 60mph using the rear brake to see if I could get the fluid to expand, but it did not appear to expand.

Glad you are OK

[Lex]

Based on a problem much like what dkgross reported but not as severe (I got home) I added a spring to push the brake push rod away from the master cylinder piston. I had the rear wheel of my brand new RD 400 Yamaha lock up at about 40 MPH from this type of problem, I really do not want to experience that again.

 

To make the spring work I had to add a tube that runs down the brake push rod from the master cylinder to just below the rubber boot. I put washers on each end (chrome on the bottom to match the push rod) to be sure nothing slipped. The total cost was a 1.49 USD, that seems like a pretty cheap fix. I'm not sure if this will pass muster for the more astatically sensitive types but I think it looks find. See attached picture.

[Guest Buddy]

I endorse the need to ensure that there is 5 to 8 mm free travel before the piston. engages (mine is set at 8), but I also tend to wash out the rear brake (between the pads and the discs) with a good cleaner like Pro Clean, followed by a very gentle water hose. I do this about every 800 to 1000 miles and you would be amazed how much muck comes out and how much it restores the brake performance

[Guest dkgross]

wow.. great info. I'll be passing it on to Micha at Moto International.

[Gio]

I just checked the clearance on my '00 V11S and estimated it at only ~1mm (as measured between the actuating rod and master cylinder) but with the rod adjusted all the way in (ie as short as possible) it was still only ~2 mm.

 

Having removed a few mm from the threaded end of the rod, it was possible to set the clearance at ~3 mm (which translates to ~ 8mm at the pedal which is where I'm thinking the 5 to 8mm should be measured..?)

 

The pedal does have some waggle as a result so adding a return spring to hold the pedal back against the stop looks like a good idea.

 

Gio

 

PS - I also use mainly the front brakes and had to replace the stock rear pads at just over 12,000 km...

[Guest gooddog]

I read the previous post, and am wondering about the rear "groan". Does anyone know if the groan is caused by the breaks themselves, or is something else moving around in there. My rear disc is always hot after a ride where the front two are not. The sound is more prominent when i'm carrying a passenger and trveling at slow speed. I'm interested to know if your(DKGross) bike ever made the groan, and what Micha at Moto I is going to do for you.

 

 

thanx, ray

[Guest dkgross]

now that I think about it, my bike did 'groan' every once in a while when I was backing into the garage.

 

Micha said they were going to pretty much replace the entire rear brake system, including the rotor (I suppose I should ask how much of this is covered under warranty, eh??)

 

I had my footpegs lowered by them (using Centauro parts), and I'm wondering if that had something to do with it...or, if I just had a messed up system to begin with...

 

he said it would take about 4-5 days for the parts to come in. Whaaaaa. It's NICE in Seattle now....it'll be raining when the bike is ready...

[Guest Bob in CT]

Check the rear axle bolt torque setting. The book says 28-30NM = approx. 22ft.lbs. Mine was at 90ft. lbs. The wheel bearing failed a 10,000 miles and my brake has always made the noise when backing out of the garage. It's only been a week with the new setting, but there hasn't been any noise from the brake. The axle nut is a lock nut, but I put a little blue loctite for piece of mind. Maybe this will save soom bearings and brakes.

 

Bob

 

 

 

Tenni

96 Sport1100

79 G5

[Lex]

Bob,

 

That is an error in the manual. The 22 Ft/Lb is for the disk carrier bolt, not the axel. If you look at the drawing of the front wheel you can see they just used the disk mount bolt setting when they made the rear wheel drawing.

 

If you look at the torque setting page you will find the rear axel is listed as something like 130 N/M, that is about 90 Ft/Lbs. Some folks have suggested that 90 Ft/Lbs is too much, I don't know about that, but I would strongly suggest you use more that 22 Ft/Lbs.

 

FWIW, the torque setting SHOULDN'T (remember, this is a Guzzi so normal laws of time, space and physics don't always apply) affect the rear wheel bearings, the force should pass through the center of the bearings and the spacer inside the wheel.

 

Cheers,

 

Lex

[dlaing]

Does anybody's rear brake disk run cooler than body termperature?

If I go for a ride on the freeway and do not use the rear brake, it still heats up to about 150 degrees fahrenheit ie. too hot to keep my hand there but not hot enough to get a burn.

The rotor is looking shiny and more worn than the front even though I am light on the rear brake.

I gave the brake freeplay and my groaning was 'fixed' along time ago by lubricating the caliber pistons.

My guess is that the pistons do not float back in enough and still exert a little pressure on the disk.

So perhaps disassembling the calibers and cleang the pistons with steel wool may reduce stickage???

I wonder if removing the rear brake would reduce fuel consumption and increase dyno output!?!?!

[al_roethlisberger]

..dunno, if you can put the bike up on a stand after the caliper/disk/pad is hot from a good ride, and you can still turn the rear wheel pretty much as freely as any other time(including brake removed)... then I'd say "no" it isn't affecting anything.

 

My rear brake "groans" a bit when rolling the bike backwards, but the disk doesn't get very hot when not using the brake. So I guess that so far, I haven't had this gremlin. I am going to go get some brake cleaner and keep a tight maintenance window on it though.

 

Time will tell though...

 

al

[Gio]

I seem to recall an earlier thread along this (rear brake drag) line...? The rear brake does appear to drag and therefore heat up even if not used.

 

I initially experienced the "rear wheel groan" also - usually when pushing the bike backwards but sometimes when just coming to a stop. During a warranty repair visit I heard mention of the need for an additional or different shim for the rear caliper (not sure if this was with referrence to the pads or the caliper mount) but there was also very little (if any) grease in the rear wheel assy. The brake side bearing was also replaced in the same visit. No more groans coming to a stop but still get the occaisional noise when reversing.

 

I replaced the stock rear pads with Ferodo FDB207R at just over 12,000 km and these are still loooking ok at just under 32,000 km so are either wearing much more slowly (or subject to less drag...?). Still have the stock front pads fitted.

 

Gio

[al_roethlisberger]

I can definitely verify that my rear brake drags a bit, just by heat alone.

 

Got back from a ride, and my front rotors were cool to the touch, but the rear was definitely warm... not hot, but very warm.

 

I think my brake pedal/lever is set appropriately, so I don't think that's the issue. I'll get some brake cleaner and wash it out vigorously when I think about it.

 

odd that they drag like this...

 

al

[Guest dkgross]

sigh..my first bad experience with the Guzzi Parts Department. It's going on my 3rd week now without my bike. Apparantly, it's hard to get a rear rotor for an 02 LeMans...sheeesh..ya'd think this would a pretty normal item to have IN STOCK somewhere.