Rear brake bracket jamming disc

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Redplexus
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Rear brake bracket jamming disc

Post by Redplexus »

Went for a ride. When I wheeled the bike out of the garage there was no brake squeal, no rolling resistance, everything seemed fine. Few miles down the road I became aware the bike was struggling to make the usual progress and throttle response was unusually laborious. Next set of lights the bike wouldn't easily roll back and forth in neutral. Soon after that I had to stop and investigate as there was a burning smell. By this time the rear brake was glowing, the disc cover had melted clean off and the fluid pressure was jamming the pads on - I let the boiling fluid vapour out in order to release the pads. then noticed that not jkust the pads but the caliper bracket itself is now jammed into the disc. How on earth could that happen while riding? Can't see any damage to the wheel/swingarm or anything else which would create any geometric deformation, but the whole wheel/disc now seems to have moved about 3mm sideways, fouling the bracket, which itself appears quite normal.

any clues? I have attached a photo showing the offending item. dammit
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Re: Rear brake bracket jamming disc

Post by jnnngs »

Hi,

My initial thought is that you have missing / incorrect spacers on the axle and the wheel is moving around.

Paul.

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Re: Rear brake bracket jamming disc

Post by cbxchris »

A seized caliper piston is probably the culprit, whip it all apart and start there, if it looks and feels free it could be no free play on the brake master cyl push rod, which would make the brake drag whilst riding , looking at the picture it does look quite severe , all the best with the diagnosis Chris

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Re: Rear brake bracket jamming disc

Post by Redplexus »

jnnngs wrote:Hi,

My initial thought is that you have missing / incorrect spacers on the axle and the wheel is moving around.

Paul.
Hi Paul, that's what I thought at first - but can't explain why the bike only started doing this after i'd already run it without incident previously and it was rolling fine when I pushed back out of the garage. I'm not that big - if this machine was reluctant to move i'd have had to ask the wife to push it instead. No shims/spacers or bushes have disappeared while riding, and the wheel bearings are not at all sloppy - everything seems ship shape and i'm now not convinced the bracket itself isn't deformed - but don't know without having a known original part to compare with....aaaaaaarrrgghh
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Re: Rear brake bracket jamming disc

Post by jnnngs »

Redplexus wrote:
Hi Paul, that's what I thought at first - but can't explain why the bike only started doing this after i'd already run it without incident previously and it was rolling fine when I pushed back out of the garage. I'm not that big - if this machine was reluctant to move i'd have had to ask the wife to push it instead. No shims/spacers or bushes have disappeared while riding, and the wheel bearings are not at all sloppy - everything seems ship shape and i'm now not convinced the bracket itself isn't deformed - but don't know without having a known original part to compare with....aaaaaaarrrgghh
But something could be moving around on the axle, fine at first then moves/moved during use - probably unlikely tho'.

I have a complete CBX (well two actually) in bits that you could compare with if you wanted to come over.

Paul.

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Re: Rear brake bracket jamming disc

Post by steve murdoch icoa #5322 »

I have actually seen a very badly adjusted chain cause this.
Have you been able to check if the brake caliper is functioning as Chris suggested or did it get cooked?
If you do get to compare parts with Paul, also have a look at the brake caliper stay arm.

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Re: Rear brake bracket jamming disc

Post by Rick Pope »

And check the return port in the master cylinder.....
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Re: Rear brake bracket jamming disc

Post by Redplexus »

thanks Steve, will do. the caliper was well cooked, disc will get replaced as I'm now not sure how reliable it may be under heavy use. it got so hot the brake fluid literally boiled off, similarly the disc shroud melted into a little black puddle then got sprayed all over the back end as it dripped onto the wheel. baffling why the geometry seems to have changed so radically though - never seen that before in nearly 40 years of riding.

cheers Rick - I've taken the 'opportunity' to fully strip and overhaul calipers, pads and pistons both ends in case there's any more unseen gremlins waiting for me. Should'nt have assumed that because it looks great and was fully functional last time I used it, that everything was still fine.
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Re: Rear brake bracket jamming disc

Post by Jeff Bennetts »

Check your wheel bearings while everything is apart!

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Re: Rear brake bracket jamming disc

Post by mlynch001 »

One thing that no one has mentioned is that the master cylinder pushrod could be adjusted "too long" This is very common on Gold Wings that had floorboards and or other aftermarket footpegs installed. However, this can happen on ANY Honda with a rear disc brake. It could be that the relief port is clogged. Having the pushrod too long creates the same symptom. I am going to assume that the sliding pins on the caliper are free? Another concern that I have is that the caliper bracket is not centered on the disk. The drake disc should be (more or less) centered, with equal distance between the bracket and the disc on the inside and outside. Your caliper bracket appears to be too far in. In your photo, it appears that the chain adjuster may be installed reversed; that flat washer and the witness line should be OUTSIDE the swing arm and not inside. Some chain adjusters had those stiffening washers welded to both sides, with witness lines on both sides, and some only on one side. IF you have the adjuster with one washer, it should be on the outside, against the head of the axle or the nut. The witness line is ALWAYS faces to the outside. Having the washer INSIDE forces the caliper bracket to the left and creates misalignment. Just some different observations.

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Re: Rear brake bracket jamming disc

Post by cbxchris »

One thing that no one has mentioned is that the master cylinder pushrod could be adjusted "too long" This is very common on Gold Wings that had floorboards and or other aftermarket footpegs installed. However, this can happen on ANY Honda with a rear disc brake. It could be that the relief port is clogged. Having the pushrod too long creates the same symptom Mlynch i have mentioned this in a previous post !

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Re: Rear brake bracket jamming disc

Post by z13phil »

Hi Redplexus, Can you tell me if you ever sorted this problem ? as i have the exact same problem down to the letter. Just need to know what the problem was and did you sort it out.
Much appreciated

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Re: Rear brake bracket jamming disc

Post by NobleHops »

Greetings Phil and welcome. I had the same problem about 10 years ago and in my case it was the return port to the cup on the rear master cylinder. It had become clogged with debris, likely from the ancient feed pipe from the reservoir. Let me see if I can search a thread for you.
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Re: Rear brake bracket jamming disc

Post by NobleHops »

Here you go:

http://www.cbxclub.com/forum/viewtopic. ... urn#p64334

As you learn your way around this site, try out the search tool upper right, with a few keywords. I found this searching on “rear brake return”, but I had a good idea those words would be present because the post I was looking for was my own :D . Anyway, you get the idea -your questions are most welcome, but you can often get further faster if you do a little searching and reading first.


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Re: Rear brake bracket jamming disc

Post by z13phil »

NobleHops wrote:
Wed Jul 06, 2022 1:28 am
Greetings Phil and welcome. I had the same problem about 10 years ago and in my case it was the return port to the cup on the rear master cylinder. It had become clogged with debris, likely from the ancient feed pipe from the reservoir. Let me see if I can search a thread for you.
Hi , many thanks for your reply. But this is not a problem with the caliper or master cylinder . If you see the picture a the top of this page, in a previous report on the same problem i have. I shows you the position of the disc and the caliper mount. This is un-even and catching on one side.
Thanks in advance :handgestures-fingerscrossed:

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