Rear brake bracket jamming disc

CBX-tras
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Re: Rear brake bracket jamming disc

Post by CBX-tras »

Always caused by something preventing the caliper piston from retracting after brake pressure applied, causing the bracket to bend and bind.
The usual suspect is crud buildup behind the square shaped o-ring in the caliper, second by the return port in the m/c.

I've recommended to customers that brake fluid should be flushed annually and all the brake components be rebuilt every 5 to 6 years.

z13phil
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Re: Rear brake bracket jamming disc

Post by z13phil »

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. It shows you the position of the disc and the caliper mount. This is un-even and catching on one side, with the caliper removed.
Thanks in advance :handgestures-fingerscrossed:

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NobleHops
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Re: Rear brake bracket jamming disc

Post by NobleHops »

Ahh, I see what you mean.

Demount the wheel and rotor and just start checking things for being square and parallel. eg put the center of the rotor on a flat surface and measure at opposite ends. See if the rotor carrier groove is parallel to the surface when the section that's clamped on the axle is held flat, etc. Soemthing is way bent back there it seems.
Nils Menten
Tucson, Arizona, USA '80 CBX, sort-of restored :-)

CBX-tras
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Re: Rear brake bracket jamming disc

Post by CBX-tras »

If the bracket didn't move (as you said) then the wheel did, after you were able to move the bike freely, without effort.
There are no shims that can fall out, only spacers that are completely captured by the axle (left/right spacers, chain adjusters, bearings, etc.)
Something isn't right or went bad. Follow Nils advice, above.
Pretty dramatic to cause so must heat to melt the splash shield, it should be obvious.
Last edited by CBX-tras on Thu Jul 07, 2022 9:03 am, edited 1 time in total.

z13phil
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Re: Rear brake bracket jamming disc

Post by z13phil »

Many Thanks

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Re: Rear brake bracket jamming disc

Post by z13phil »

NobleHops wrote:
Wed Jul 06, 2022 5:53 pm
Ahh, I see what you mean.

Demount the wheel and rotor and just start checking things for being square and parallel. eg put the center of the rotor on a flat surface and measure at opposite ends. See if the rotor carrier groove is parallel to the surface when the section that's clamped on the axle is held flat, etc. Soemthing is way bent back there it seems.
Thanks Nils, Just wondering if someone put a spacer in wrong. If you go to the start of this thread, another member posted a picture who had exactly the same issue. I would upload a photo but i don't know how to. Regards

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Re: Rear brake bracket jamming disc

Post by jnnngs »

z13phil wrote:
Wed Jul 06, 2022 7:10 pm
NobleHops wrote:
Wed Jul 06, 2022 5:53 pm
Ahh, I see what you mean.

Demount the wheel and rotor and just start checking things for being square and parallel. eg put the center of the rotor on a flat surface and measure at opposite ends. See if the rotor carrier groove is parallel to the surface when the section that's clamped on the axle is held flat, etc. Soemthing is way bent back there it seems.
Thanks Nils, Just wondering if someone put a spacer in wrong. If you go to the start of this thread, another member posted a picture who had exactly the same issue. I would upload a photo but i don't know how to. Regards
I helped the original poster fix the issue - he lived close to me. It turned out to be the wrong rear disc - probably a CB900 one, which looks the same but has a different offset. As a result, didn't line up in the centre of the caliper.

CBX-tras
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Re: Rear brake bracket jamming disc

Post by CBX-tras »

If it was the wrong disc, how was this statement correct?

"When I wheeled the bike out of the garage there was no brake squeal, no rolling resistance, everything seemed fine."

Many of us where scratching our heads.

Whatever........... glad you got it sorted.

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Re: Rear brake bracket jamming disc

Post by z13phil »

jnnngs wrote:
Thu Jul 07, 2022 3:31 am
z13phil wrote:
Wed Jul 06, 2022 7:10 pm
NobleHops wrote:
Wed Jul 06, 2022 5:53 pm
Ahh, I see what you mean.

Demount the wheel and rotor and just start checking things for being square and parallel. eg put the center of the rotor on a flat surface and measure at opposite ends. See if the rotor carrier groove is parallel to the surface when the section that's clamped on the axle is held flat, etc. Soemthing is way bent back there it seems.
Thanks Nils, Just wondering if someone put a spacer in wrong. If you go to the start of this thread, another member posted a picture who had exactly the same issue. I would upload a photo but i don't know how to. Regards
I helped the original poster fix the issue - he lived close to me. It turned out to be the wrong rear disc - probably a CB900 one, which looks the same but has a different offset. As a result, didn't line up in the centre of the caliper.
Brilliant, that would explain it. When I think it only has to be 3mm different and it would cause this problem. :clap:

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