Rhythmic clank-clank-clank when rear brake applied...

[Mazz]

On way home last night, I applied the rear brake while approaching a red light and I noticed a rhythmic clank-clank-clank coming from rear wheel.

First thought was that the old rim had a split in it & the split was hitting the rubber brake shoe. When I stopped to look, it wasn't that, I couldn't see anything wrong, so rode on. Applied the brake again - same noise, clank-clank-clank.

When I got home, I noticed there was a lot of lateral play in the caliper "jaws" (in direction of yellow arrow, see pic)...if I held the brake adjuster cam between finger and thumb it would wiggle about 5mm.

I (rightly or wrongly) tightened up the hex on the opposite side (red arrow), thinking this would fix it, but same thing happened again this morning.

Any idea how to fix this problem? Thanks

 

[T4tomo]

It might be a slightly buckled rim

 

[Paulus]

As there is lateral movement, is the retaining bolt that holds the mudguard and caliper assembly loose? Check the rim again for any links.

 

[Mazz]

As there is lateral movement, is the retaining bolt that holds the mudguard and caliper assembly loose? Check the rim again for any links.

You mean the bolt that's sort of around the back (green arrow)? I'll check it later.
Mudguard is only held on by tie-wraps btw.

 

[Mazz]

It might be a slightly buckled rim

I'll spin it by hand later and see if it looks wobbly.

 

[Paulus]

You mean the bolt that's sort of around the back (green arrow)? I'll check it later.
Mudguard is only held on by tie-wraps btw.
View attachment 740230

That's the one.

By doing the other bolts up you might find the calipers are too tight and don't release properly.

 

[Ming the Merciless]

How worn is the rim? Looks to be a distinct groove in it.

 

[Mazz]

How worn is the rim? Looks to be a distinct groove in it.

I don't know how to measure the wear, but I'll take a close-up pic later.

 

[Mazz]

It might be a slightly buckled rim

I spun the back wheel and watched the gap between brake shoe and rim. The gap was cyclically going big then small, so I think wheel must be mishapen.

As there is lateral movement, is the retaining bolt that holds the mudguard and caliper assembly loose? Check the rim again for any links.

That bolt was tight, not loose.

I checked wear on the rim. There's plenty of ridges on there then I noticed it's starting to split, so I need to replace it. At least I know I've got my money's worth out of it.

I will replace the rear wheel and see if I still get the noise problem.

Thanks all.

 

[Paulus]

I spun the back wheel and watched the gap between brake shoe and rim. The gap was cyclically going big then small, so I think wheel must be mishappen.

That bolt was tight, not loose.

I checked wear on the rim. There's plenty of ridges on there then I noticed it's starting to split, so I need to replace it. At least I know I've got my money's worth out of it.

View attachment 740288

I will replace the rear wheel and see if I still get the noise problem.

Thanks all.

That would seem to be the cause.

 

[T4tomo]

I will replace the rear wheel and see if I still get the noise problem.

that's only likely if you deform the new wheel rim and put a split in it

First thought was that the old rim had a split in it & the split was hitting the rubber brake shoe. When I stopped to look, it wasn't that, I couldn't see anything wrong, so rode on.

Oh yes it was......

 

[Ming the Merciless]

You should periodically measure rim thickness and also use a straight ruler to check for concavity. Essential for rim brakes. Not a problem with disc brakes. I used to go through rims once every two years in my rim brake days.

 

[Mazz]

View attachment 740337


Oh yes it was......

Note to self: Check both sides of wheel next time.

 

[Mazz]

You should periodically measure rim thickness and also use a straight ruler to check for concavity. Essential for rim brakes. Not a problem with disc brakes. I used to go through rims once every two years in my rim brake days.

Good advice.
This wheel's lasted me nearly 7 years of daily use, so I can't complain.

 

[fossyant]

You should periodically measure rim thickness and also use a straight ruler to check for concavity. Essential for rim brakes. Not a problem with disc brakes. I used to go through rims once every two years in my rim brake days.

Gone through a rear in 12 months on my commuter - back wheel does get covered in grit though (washed after every wet commute). @Maz, that wheel is worn out, hence the split appearing at the rim joint. They go with a big bang (I've done it).