Commuting - noisy brakes as horn . . .

I'm the worlds worst mechanic. I installed some new brake pads the other day and probably did not get the taper right because they are noisy, like a gaggle of geese, no more angry than that, more like a battalion of geese. I'm also lazy so I have not bothered to adjust them. Last night, I approached a somewhat weird situation on my eve commute. Sort of like a Mexican standoff. Car attempting to pull out of parallel parking spot. Car in front of me waiting for him to pull out. Car in oncoming lane stopped to make a left hand turn. Who will move first. Instead of waiting for them to sort it out, I whipped around the right of the car in front of me. At the instant I came around, the car pulling out of the parking spot decided to whip a 180. I grapped my brakes and they made such a terrible squawking sound the guy stopped in his tracks and I proceeded. He even had his window rolled up. I thought, "Wow, cool". So now I'm wondering if I can use the squeaky brakes to my advantage. I'm just leaving them like that for awhile to see how it works. I notice at high speeds, I can flutter them and almost get an octive, like an English ambulance. Woo-Hoo! :p

You'll have better stopping power&control if they don't squeell.

I've suspected truck drivers with air brakes do this a lot. Hey that's what we need to use as a horn an air brake sound.
-;)
Joe

Nothing wrong in my book with using brakes as a signaling device. I've got disc brakes on my commuter, and if I put just the right pressure on the front set I get a tone out of it. Sort of like running one's finger around the top of a water filled glass; though, not as pleasant a sound.

Where the brake noise helps is when I come around a blind corner to the spot under a bridge where indigents hang out while waiting their turn to panhandle the nearby car offramp. If I do it right, I get a good tone as I come around the corner and I can skip yelling at them to clear the path. The last thing I want is to have a bunch of angry homeless types on a vandetta against me or some other unsuspecting cyclist.

Hey that's what we need to use as a horn an air brake sound.

I used to have an air horn on an old car of mine (was there when I bought it) - noisy as hell, but people sure paid attention. Maybe we should all just throw those little air horn cans on the handle bars for the commute........

I've been trying to get my rear brake to squeal and my front brake to not squeal. But after a while with all the sand and dust, they just brush over pretty silently now.
The brake squeal is probably the single most noticable sound that tells pretty much everyone that a) I'm here, b) I see you and I'm taking action and c) pay attention cause I am.

You'll have better stopping power&control if they don't squeell.

That's not really true... at least, not to a measurable extent. Squealing car brakes are a bad sign, yes, but it's merely an annoyance (or a horn! ;)) on a bicycle. Rim brakes always pulse while in action - they grip and release, grip and release at a very high frequency. If it's at the right frequency, this will be audible as a high-pitched squeal. In a certain sense, brake squeal is a good thing - it means that your brakes are doing their job! From an aesthetic perspective, it's nice to not hear 'em shrieking whenever you squeeze the lever, so we try to reduce or eliminate the squealing with toe-in, etc.

It's not the pulsing at whatever frequency that causes it, it's a resonance.

Due to design weakness the cantilever front brakes on my Lemond Poprad squeal fanstastically, especially if a bit damp. No amount of adjustment or pad swapping is known to fully cure the problem. I can fix it temporarily, but it will start squealing again after 20mi or so of brake wear.

So I've come to look to the bright side of the squeal and yes, it does work like a warning horn and I use it as such fairly often, almost daily.

But the downsides:
-Makes me feel like I'm waking up the neighbors in residential neighborhoods at 6am at every stop.
-Makes me sound like a horses rear side when riding downhill on single track. You know that guy you hear from a mile away up the hill that squeals on every turn.
-Main issue: I have developed a habit to use my rear brakes more than I should to avoid the squeal.

Al

maybe we could make a horn that had a squeaking brake sound, that way we get the psychological benefits of the i'm not really honking at you but get out of my way but also brake quietly when stealth is important?

It's not the pulsing at whatever frequency that causes it, it's a resonance.

Hrm, can you explain how this is different? I'm not trying to pick a fight, it's just that I'm not really using particularly technical terms here... are you sure we're not talking about the same thing? I was under the impression that it was the high-frequency vibration of this grip-release cycle that caused brake squeal.

That's not really true... at least, not to a measurable extent. Squealing car brakes are a bad sign, yes, but it's merely an annoyance (or a horn! ;)) on a bicycle. Rim brakes always pulse while in action - they grip and release, grip and release at a very high frequency. If it's at the right frequency, this will be audible as a high-pitched squeal. In a certain sense, brake squeal is a good thing - it means that your brakes are doing their job! From an aesthetic perspective, it's nice to not hear 'em shrieking whenever you squeeze the lever, so we try to reduce or eliminate the squealing with toe-in, etc.

I can't describe the action very elloquintley (nor can I spell), so I'll cut & paste a link to the explanation written by Jobst Brandt. In summation, basically, we're both correct. Brakes need to chatter (or squeal, pulse, resonate whatever), it's the frequency of the resonance that matters. If the frequency is low, we can hear it (as you explain), but they are not doing the job optimally (as I attemped point out). I submit that there is a noticeable (measurable) differance on a bicycle.

Jobst Brandt on Brake Squeal (http://www.sheldonbrown.com/brandt/brake-squeal.html)

It's not the pulsing at whatever frequency that causes it, it's a resonance.


Hrm, can you explain how this is different? I'm not trying to pick a fight, it's just that I'm not really using particularly technical terms here... are you sure we're not talking about the same thing? I was under the impression that it was the high-frequency vibration of this grip-release cycle that caused brake squeal.


I have a degree in music, and I know what resonance and vibrations are. You guys are indeed saying almost exactly the same thing, in different words.

Ah sorry ok.
I'm not sure about music, but for me, yes you're right, they're almost the same.
It's like saying "automobile" and "sedan".
A resonance is a specific type of vibration that causes the objects in question to respond at some natural frequency or some order of that to cause a greatly amplified vibration (which is what's causing the squealing of the brake).
All systems vibrate, the key to letting the car know you're there by squealing is to set it up so that the vibration is amplified under certain conditions, in the case of my bike, it's when the wheel's spinning at a certain speed and there's a certain amount of pressure on the brake shoes.
It's like blowing into a jug, it'll vibrate but when you get to that "special" frequency, you can really hear it.

Wind normally causes a bridge to vibrate... but when you hit that "special" frequency..

http://www.civeng.carleton.ca/Exhibits/Tacoma_Narrows/DSmith/fig06.gif
http://www.civeng.carleton.ca/Exhibits/Tacoma_Narrows/DSmith/fig07.gif

If anyone can find the video, the tacoma narrows bridge was flexing like a noodle shortly before it collapsed.

Ahh yes, the infamous Tacoma Narrows Bridge. A lesson in many a physics class.
Here is a .mpg video clip:
Pretty cool/scary!

http://www.civeng.carleton.ca/Exhibits/Tacoma_Narrows/TacomaNarrowsBridge.mpg

Sometimes my brakes squeek randomly, like they've been working fine with no squeeks for a month, and then one day they sqeeek. The next day they're fine again. Wierd.
But yea, sqeaky brakes make excellent warning noises for peds/cars.

I have an twenty year old wheel with that black coating that was popular in the '80's. At moderate brake pressures, it howls at painful levels. So, I tend to NOT use it at all, or use it for "hard" stops...it is quiet under heavy pressure.

But, I have found it useful on bike trails. There are often middle-aged couples walking on the trails around sunset. They walk side by side, blocking the entire trail. If you say "on your left" they just get confused and start staggering in circles. But, when they hear that brake "howl" they promptly step out of the way. Very useful.

I used to toe-out my rear brake so it squeels when lightly touched, while I used to ride the "bike" paths. It certainly worked much beter than polite calling out, when I needed to warn people that there is a bike behind them. I finally decided that I prefer to deal with cars on the road, so I toed the brakes in to quiet them.

I click my brake levers a few times well in advance to warn people I'm coming. That works well for me on Class I bike trails.

It snowed/rained last night and my beautiful shrieking brakes have been silenced.

Get the brakes fixed and get a zound Air horn.

Get the brakes fixed and get a zound Air horn.
True the Zound is much more effective, plus your brakes will work better

I'll drink to this. The cantilevers on my Crosshairs are loud and their is nothing I can do about it. They are only quiet when they are well out of adjustment. It works the right way round as the harder I break the louder the sound, both front and back. Great during my general commuting in the city, bad life is calm or when I am cycling out of my neighbourhood at 6:00 in the morning.

My other bikes don't do this unless I have the brakes really badly out of adjustment.