tiger1964 

I had an “interesting experience” on a ride on Wednesday. I had been hearing an odd little noise for a mile or so but could not identify it; then I needed to stop at one of the few stop signs on this rail-trail, downhill and a relatively blind intersection. I hit the brakes and FLING! the front caliper came off, only kept with the bike due to the cable. The caliper battered against the forks and front wheel and I expected the wheel to lock and throw me over the handlebars. Amazingly I got the bike stopped with a foot or so to spare, no spokes broken (although later I saw the wheel was a bit out of true), the chrome of the fork unhurt and the caliper not even scratched! OK, I lost the caliper retaining nut. Anyway, carefully rode home.

This has never happened to me in over 50 years of cycling. Probably should have made a thorough start-of-season inspection but the bike has been so problem-free. No idea if the front caliper had a Nylock-insert nut (it does now!), the rear did not. By the way, Suntour Superbe brakes and Kool Stop pads.

Anyway, despite toe-in, I have been getting brake squeal but I basically ignore it. But I’ve been thinking; the squeal — is this a manifestation of a vibration, and could it have caused the nut to vibrate loose after a year (since the bike was assembled)? I've had Mafacs you could hear from the next zip code, but never experienced a caliper jettisoning. Not sure of the exact number of millimeters’ toe-in that would stop the squealing, but I’m considering adding more.

steelbikeguy

Your situation is certainly extreme, and there's not much chance of knowing the cause with any certainty, but it seems reasonable to me that the squealing could have been a factor in the nut coming loose. Of course, squeal can be a sign of things/parts having too much play (such as the brake pivot), so it seems possible that the squeal could have been caused by a loose nut.

My only relevant data point is the Campy NR sidepull front brake on my Olmo. For some reason, it started squealing. The squeal was bad enough to cause the quick release lever to rotate while I was braking, causing a gradual decrease of braking. I think I fixed it by filing the pads to increase the effective toe-in, but the squeal has since been eliminated.

I suppose the lesson is to not permit squealing to continue. While the odds of serious mechanical failure are small, it does reduce braking effectiveness.

Steve in Peoria

nlerner

There’s likely a relationship between squeal, vibration, and loosening of hardware, but, then again, all of those aforementioned MAFAC brakes would be flying off left or right if the relationship was strong.

Bianchigirll 

Just one more question.....Does your wife know what an allen wrench is?


Sorry I couldn't resist, I think I watch too many cop shows

SurferRosa

I would never use a brake or pad that made any kind of regular noise. That's just bad mechanics ... and lack of pride.

​​​​​​Glad you're okay.

tiger1964 

Actually, she does, but I would not trust her with one. And if you'd seen her shifting a Campy Nuovo Record RD like it was a ball pein hammer, you'd understand. Healthy, athletic... but not mechanically sensitive.

merziac

Just going to throw this out but I would take the coarse file to the pads, scotch brite and brake clean to the rim, then one or the other if it persists, you could also try the cleaning, scuffing before the file too.

I actually like to use the nastiest solvent/cleaner I have on hand, most of the good stuff is gone now with toothless swill in its place.

I fully realize why that is but as a flat rate tech, the extra time and effort comes straight out of your pocket and many cleaning operations need to be as stringent as possible, many cleaners now days make that nearly impossible and very costly timewise.

randyjawa 

Brake squeal is a product of the pad or pads touching the rim back first, as opposed to front first. Look closely at how the pads are contacting the rim. If one or both pads touch back first, that it more than likely the problem. That said...

Lucky for me I did not go head over heels when the front caliper fell off and into the front wheel on this three wheeler. The caliper, still attached to the brake lever, got snagged in the spokes, bringing the front wheel to an immediate stop. I was virtually vertical before, lucky for me, dropping backwards on the wheels. The problem was me being to excited to try a new find out without first checking to see if the bike was safe to ride...


If you look closely you will see that there is not nut on the caliper mounting bolt. Lucky for me I was not even up to walking speed when I tested the brake. That said, once I had checked the bike out properly it proved to be a hoot to ride with is articulated rear end.

tiger1964 

Well, this is strange and perhaps interesting. I reattached the brake using a Weinmann brake's nut -- fortunately the same threads -- and really tightened it down; then took it out for a ride. No squeal? Perhaps it had been a wee bit looser than needed all along, and it took a year before it came off? I find that a little hard to believe, but I have to realize I have observational evidence.

Is this yet another bike part that needs Loctite?

merziac

Maybe on the loctite, I just use a drop of super glue.

Glad you got it sorted quick, harmonics and resonance are tricky pita players.

Seen many a noise, leak and squeak tech lose their shirt chasing them on cars.

tiger1964 

Presumably the front brake's nut is in tension, the rear brake's nut is in compression. Different stresses, different results.

That said, glad I did not have a serious crash just before my 66th birthday, not sure how my bones would have handled it.

dddd

Vibration is one thing, it can cause a loose nut to spin free, but if the nut was near as tight as it should have been then no braking forces (including cyclic grabbing/chattering) should result in any change in the bolt's tension since the hub of the center bolt is fixed solidly against the crown at all times.

Some kind of threadlocker, Nylock or lockwasher is always good insurance and all modern bikes seem to have stuff on the bolt threads.