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Offline wilbert

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Clunk from rear end when applying rear brake
« on: June 27, 2018, 03:32:37 PM »
I keep getting a loud clunk when swapping from front to rear brake. I use the front brake and then when the speed drops to 10mph or so I use the rear. When releasing the front and pressing the rear there is a loud clunk but not everytime. Is it because the brakes are linked? Or should I be doing some checks? The brakes work well but the noise makes me a little uneasy.

Online Bree

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Re: Clunk from rear end when applying rear brake
« Reply #1 on: June 27, 2018, 09:05:18 PM »
It depends on how confident you are with the spanners. From your description I would say it does need checking. I would put it on its main stand, then you can move the wheel, whilst looking to see if you can spot any thing that is making the noise, when you apply the rear brake. The rear caliper should have some movement, but should not have a loud clunking noise. If you cannot see anything then a visit to the workshop I think. It could also be the pads moving in the caliper thats causing the noise. Let us know what the outcome is.....  :305: :305:
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Offline Tony XR se

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Re: Clunk from rear end when applying rear brake
« Reply #2 on: June 28, 2018, 10:46:42 AM »
All my pads front and rear float about a bit and make a gentle tapping sound  and I can only hear that if I'm moving the bike by hand ...

I'd agree have a look into it

Offline Arbourtek

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Re: Clunk from rear end when applying rear brake
« Reply #3 on: June 28, 2018, 12:56:37 PM »
A click would be acceptable, as the pads are able to move within the caliper, but a clunk needs looking at. Before you ride it to a workshop though check the basics such as caliper,  and rear arm security. take care!
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Offline skapan

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Re: Clunk from rear end when applying rear brake
« Reply #4 on: June 28, 2018, 06:08:36 PM »
OP doesn't say how many miles on the bike, could it be the damping elements in the sprocket hub?  Does it clunk in a similar manner when shifting?

Online Bree

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Re: Clunk from rear end when applying rear brake
« Reply #5 on: June 28, 2018, 06:52:56 PM »
*Originally Posted by skapan [+]
OP doesn't say how many miles on the bike, could it be the damping elements in the sprocket hub?  Does it clunk in a similar manner when shifting?



Could be, I did suggest putting it on the main stand. At least that way he could turn the wheel and look and listen for any noises.
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Offline Low-Brau

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Re: Clunk from rear end when applying rear brake
« Reply #6 on: June 28, 2018, 08:27:14 PM »
I have something similar:

I will initially begin braking with the front brake.  As speed bleeds off, I begin applying rear brake.  As I do this, I can feel a wobbling or vibration in the rear-brake foot lever.

My XR has done that since I bought it, and I've always assumed (in my own mechanically worthless brain) that it was the linked brakes sort of... I dunno... catching up to each other?  :084:

That said, if you have a Clunk, I'd think you may have a sticky caliper piston or pusher. It may need removal, cleaning, and replacing the seals.  Not a small or clean job to do.

My previous Honda did this to me a lot.
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Offline wilbert

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Re: Clunk from rear end when applying rear brake
« Reply #7 on: June 28, 2018, 09:30:21 PM »
Bike has covered just over 1000 miles as I have only had it a month. I have been riding in dynamic pro since the 600 mile service and only started to get the clunk then. maybe it is something to do with the ABS being turned right down or the linked system. It isn't the sound of the pads / floating disks moving. Will be weekend before I get chance to have a look at it as I'm on nights at the moment and trying to sleep in the daytime heat is about all I'm capable of at the moment. The clunk only happens after going from front brake lever to the rear brake. I can jump on the rear brake and it wont happen but gentle (normal) application does it almost every time. Is there some sort of change over valve in the ABS unit that allows the rear brake to work independently? The linked system is all new to me.

Offline skapan

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Re: Clunk from rear end when applying rear brake
« Reply #8 on: June 28, 2018, 09:57:04 PM »
I have no further ideas, I must admit that I haven't used the rear brake once on my XR in 16,000 km. But if I can remember, next time I'm out I'll try to replicate your issue.

Offline Low-Brau

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Re: Clunk from rear end when applying rear brake
« Reply #9 on: June 28, 2018, 10:01:21 PM »
*Originally Posted by wilbert [+]
Is there some sort of change over valve in the ABS unit that allows the rear brake to work independently? The linked system is all new to me.

I'm not sure if BMW is any different than other manufacturers, but typically in a linked brake system there are an more than one pusher on each caliper.  The system will apply lesser force to the brake not being activated by the rider.

So, for instance: If you squeeze the front brake lever, there will be two pistons closing the front brake, and only one piston closing the rear brake.  If you apply the rear brake and no front brake, two pistons will clench the rear caliper and only one will close on the front caliper.

Difficult to explain.  Easier to draw.  :187:

In my own experience, my Honda had three pistons in each caliper.  The single rear piston that linked to the front would hesitate as I applied front brake and then suddenly clunk into place on the rear.

The XR only has two pistons per caliper, I believe.
-Erik

"...but the XR is a sports bike on stilts!"
  -- zbdmark