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Brake Problem


Woodie

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2001 R1100RTP, 70,000 miles.

Symptoms:

I have not changed the pads since I got the bike at 60,000 miles.

Stopped by dealership, he said: rear pads shot, replace the rear pads.

Came home, when spinning rear wheel, can hear metal/metal dragging. and feel drag.

Replace the pads, per Clymer. (remove calipers, remove pads, clean). Pistons were hard to push back in (used pliers), but were smooth in moving. Greased the piston heads (lightly), inserted pads, replaced caliper on rotor, bolted up.

 

Now: The brakes "work"...I can spin the wheel, but hear the "dragging" sound still. Push on the pedal, the wheel stops/unable to turn it. Release pedal, can turn the wheel again, with noise.

 

Question:

Is this noise/drag normal? I thought the rear wheel should spin freely when up on the center-stand. I suspect this is why my rear brakes (which I thought had plenty of miles left on them) went through the rear pads so quickly.

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Some drag is normal on all disk brakes. On the Internet it's of course hard to judge yours, but if you can easily turn the wheel and only hear contact noise vs. feeling significant resistance, it's probably just fine.

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Thanks for the quick reply. I was afraid I might have to replace caliper or brake lines.

<phew>

has the brake fluid ever been changed? (since youve owned it?)..Brake fluid absorbs moisture over time ..esp with the heat cycle..causing the fluid to solidify ..therefore hindering caliper piston return....somewhat
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ShovelStrokeEd

There is nothing to retract the pads from the disks after application of the brakes but the runout of the brake disk. It has to be this way so that application of hydraulic pressure will immediately begin to apply the brakes. In other words, the pistons will only retract when pushed upon.

 

Now, you can do a couple of things to insure that they drag at the minimum. First is to be sure the mounting pins are clean and that the holes in the backing plates of the pad are clean as well. Should not be a problem with new pads but I always like to deburr the mounting holes on the pads creating a small

chamfer at the edges.

 

Another point where there may be problem is the outer rim of the piston calipers. At 70K miles it is likely that there is some corrosion/buildup of brake dust on the surface of the pistons. The new pads are now pushing those pistons further into the caliper body than they have been since the last new pads were installed. If the pistons are not thoroughly cleaned at full expansion prior to installation of the new pads, you could see extra resistance to retraction.

 

Renewal of brake fluid (as mentioned) and a thorough bleeding also help matters.

 

It is important also to check your brake fluid level in the reservoir. If the new pads push the pistons substantially further into the caliper, the fluid reservoir could become overfull and that could inhibit retraction leading to some drag.

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Woodie, slight drag from a freshly re-padded disk brake system is normal.. The only means of the pads retracting away from the rotors (after hydraulic pressure is released) is the designed in histreses (sp) of the piston seals.. A lot of development work goes into proper seal material & design to get just the right amount of pad retraction after HOT brake release.. Obviously any rotor warping or rotor hub displacement can add to pad kick back but on perfect rotors with no wheel bearing play & no hub flex retraction is basically controlled by piston seal design & material..

 

Your present condition does seem normal on freshly replaced pads..

 

If you are still worried about excess brake drag I would suggest you ride the motorcycle a few miles without using the rear brake (in your case that would be not using any braking, even the front).. Use the rear brake pedal for a couple of VERY LOW SPEED light stops to allow the rear pads to cycle into full rotor contact, then ride without using the brakes for a few miles (basically coast to a stop using just engine braking & down shifting).. If the rear brake rotor/caliper remains cool after coasting to a stop, then you don’t have any rear brake drag or unwanted friction on the rear brake system.. If you have heated rear brake parts even after coasting to a stop then you will need to address that issue with further & a more through inspection of the rear brake parts & hydraulic system..

 

Twisty

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To everyones posts:

 

Has the brake fluid ever been changed?

Yes. Changed at the fall Tech Daze, and the fluid (at the caliper and the reservoir) is clear.

 

If the pistons are not thoroughly cleaned at full expansion prior to installation of the new pads, you could see extra resistance to retraction.

I cleaned w/ soft cloth and brake cleaner, hopefully that was enough. Next time I change the pads, I will make sure to clean the pistons *before* pushing them back into the caliper. Fluid level in the reservoir was a bit low before starting (but not spongey), and was fine afterwards (no spills!).

 

(in your case that would be not using any braking, even the front)

Not true. I have unlinked brakes. smile.gif Good procedure, and once the weather gets above 20F, and the snow is off the driveway, I'll do that.

 

Thanks all. clap.gif

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If you could push the pads back by hand then it's fair to say the pistons aren't siezed. A disc brake has no pull off springs like a drum has. The slight flex in the rubber piston seals is all there is to pull the pads back (and any slight disc runout there may be). If the wheel spins freely with a slight rubbing sound then all is pretty much OK.

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Don_Eilenberger

If things didn't change between ABS-II brakes and whizzy brakes - isn't the rear caliper a single-piston sliding caliper design?

 

Looking at: http://www.realoem.com/bmw/showparts.do?...hg=34&fg=10

 

it looks like it. On a sliding caliper design, it is important to lubricate the sliding pins and make sure the part sliding can move easily relative to the mount.

 

Just a thought.... YMMV and all that..

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Based on what I *saw*:

 

It's a single caliper, with two pistons, both on the same side. There's some sort of self-adjusting/spring loaded mount, which appears to keep the pads centered over the rotor. The mount moves smoothly, though obviously with some resistance.

 

I did lubricate the (single) pin with lithium grease.

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Don_Eilenberger
Based on what I *saw*:

 

It's a single caliper, with two pistons, both on the same side. There's some sort of self-adjusting/spring loaded mount, which appears to keep the pads centered over the rotor. The mount moves smoothly, though obviously with some resistance.

 

I did lubricate the (single) pin with lithium grease.

OK - it's a sliding caliper. Could the resistance you feel to movement be the cause of the brake drag?

 

I think I'd use other than a plain lithium based grease in this application since brakes can heat up considerably. I'd want something that is rated for high temps (say around 400F+ or so..)

 

Best,

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