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Living Car Free Do you live car free or car light? Do you prefer to use alternative transportation (bicycles, walking, other human-powered or public transportation) for everyday activities whenever possible? Discuss your lifestyle here.

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Old 04-17-14, 12:20 AM   #1
bragi
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Question about disc brakes

I recently bought a new bike with disc brakes. In fact, I bought it just for the disc brakes. I wanted to avoid having to buy rims every 12-18 months, and I also got tired of squealing rim brakes in this wet climate. (And I wanted a new bike just because I was feeling self-indulgent.) I'm pretty happy with the disc brakes overall: they require much less cleaning/maintenance, and they have great stopping power even when soaking wet. However, they still make noise. They make faint scraping sounds when totally dry, and they do make a squeaking noise when wet or when I'm riding at low speeds. It's an improvement over rim brakes, but they're not the totally silent brakes I was hoping for when I bought this fairly expensive bike. Is this normal for disc brakes? Is there something wrong with them? Am I being unrealistic?
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Old 04-17-14, 01:19 AM   #2
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I'm told the squealing is normal, though my discs don't always do it. But I've never noticed any scraping sound from them. I know what you mean, though, because the brakes on my motorcycles always made a faint scraping sound.

I should say, squealing when the brakes are applied is sometimes normal, but not at times when they aren't actually in use. I'm not sure which you meant.

Last edited by ro-monster; 04-17-14 at 01:23 AM. Reason: clarification
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Old 04-17-14, 04:40 AM   #3
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Which brakes do you have? There are a few different types and several different models out there. None of my personal bikes have disc brakes, I prefer roller/drum brakes. But I work on several that do have discs. All disc brakes appear to have a very slight amount of drag even when adjusted properly. Seems to be caused by slight run out in the disc as well as slightly unevenly worn pads. You may have more sensitive hearing than others too. My hearing sucks, and I usually have no problem ignoring rattles and such that drive other people nuts.

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Old 04-18-14, 12:46 AM   #4
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Which brakes do you have? There are a few different types and several different models out there. None of my personal bikes have disc brakes, I prefer roller/drum brakes. But I work on several that do have discs. All disc brakes appear to have a very slight amount of drag even when adjusted properly. Seems to be caused by slight run out in the disc as well as slightly unevenly worn pads. You may have more sensitive hearing than others too. My hearing sucks, and I usually have no problem ignoring rattles and such that drive other people nuts.

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I tend to be a perfectionist in other areas of my life, and I'm afraid this leaks into my bicycling life as well. I don't think it's unreasonable to expect bicycle brakes to not make an inordinate amount of noise. Car brakes don't squeal like demented cats, and bike brakes shouldn't, either.
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Old 04-18-14, 10:33 AM   #5
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The only disc brake I've ever had, other than an ancient Phil Wood disc that is an entirely different creature, is on one of my tandems. It has never squealed. Occasionally, there is an audible rough-sounding noise (sort of like someone sanding wood with fine sandpaper) when the brake is not being applied. I put this down to the disk getting a bit warped from use. It doesn't cause noticeable friction, so I ignore it.
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Old 04-18-14, 10:47 AM   #6
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Car brakes don't squeal like demented cats, and bike brakes shouldn't, either.
The ones in our '75 VW Rabbit did, but only when the brakes were not being applied. Spraying some light adhesive to the backs of the brake pads would quiet them down for awhile but eventually the squeal would return.
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Old 04-18-14, 07:46 PM   #7
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Old 05-12-14, 09:13 PM   #8
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Again, what brand of brakes are you running? My Shimano mechanicals squeal a little bit when dry, but are totally silent when wet. On the flipside, I've ridden multiple bikes with Tektro Novela discs and they squeal a little when dry, and scream like a witch being boiled in oil when wet.

Depends on brand, but noise is normal. Motion energy has to go somewhere...
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Old 05-13-14, 07:18 AM   #9
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Heat, light, sound - typically all three.

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Old 05-13-14, 08:47 AM   #10
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You just don't hear them on cars and trucks, because they are so covered up........ They make noise.
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Old 05-13-14, 09:15 AM   #11
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I also was under the impression most cars us hydraulic drums?

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Old 05-13-14, 09:43 AM   #12
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Drums are becoming less and less common on cars; they're old technology. Every vehicle produced since probably the mid-80s has had disc brakes on at least the front wheels.
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Old 05-13-14, 10:12 AM   #13
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Ah! I would have thought it to be the other way around.

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Old 05-15-14, 08:55 AM   #14
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I also was under the impression most cars us hydraulic drums?

M.
Very few. I just did a quick check and out of 7 vehicles in my view only one has rear drum brakes, it is a 1996. I have a couple of old trucks that still have drums on all four corners, they aren't known for their stopping ability.

As far as bicycles... I have none with disc brakes, 5 with drum/roller brakes, several with coaster (sort of a drum) and a whole bunch with the rim brakes.

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Old 05-15-14, 12:01 PM   #15
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I recently bought a new bike with disc brakes. In fact, I bought it just for the disc brakes. I wanted to avoid having to buy rims every 12-18 months, and I also got tired of squealing rim brakes in this wet climate. (And I wanted a new bike just because I was feeling self-indulgent.) I'm pretty happy with the disc brakes overall: they require much less cleaning/maintenance, and they have great stopping power even when soaking wet. However, they still make noise. They make faint scraping sounds when totally dry, and they do make a squeaking noise when wet or when I'm riding at low speeds. It's an improvement over rim brakes, but they're not the totally silent brakes I was hoping for when I bought this fairly expensive bike. Is this normal for disc brakes? Is there something wrong with them? Am I being unrealistic?
I'm in the same boat as you, I was told that a slight noise isn't terrible, and because they're such a hassle to align perfectly, you might get more scrapping/noise initially until the pads wear slightly.
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Old 05-15-14, 12:38 PM   #16
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So, a faint rubbing sound when the wheel is spinning freely is natural? The noise from my rear brake is ever so slight, but any resistance seems undesirable. Mine are quiet (no unnatural sounds, like squeaking), front and back, when brakes are applied.
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Old 05-15-14, 12:40 PM   #17
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I'd like to transition away from rim brakes myself, but I don't think it is very easy with most off-the-shelf bikes (Big box store or otherwise) since there isn't any solutions that don't require a fork setup for tabs of some kind.

M.
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Old 05-15-14, 12:40 PM   #18
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Cable operated, or hydraulic disc brakes?

Setting up disk brakes is a bit tricky, and even having worked on hundreds, it is still not one of my favorite jobs. The how-to vids say loosen the lateral adjustment bolts, squeeze the brake lever to center the caliper, tighten the bolts and your brakes will now be perfectly aligned and noise free.

BS.

This is rarely the end of adjusting brakes. Sometimes, I've encountered calipers that shift while you are tightening them, probably because the top and bottom surfaces of where they bolt to the mounts are not parallel to each other, but rather on an angle which forces the brake out of alignment once the real tightening begins. Usually, I'll loosen the bolts so that there is still plenty of friction but I can also move the caliper a bit, and then adjust by sight so that there is daylight showing on either side of the disk between the disk and the pads. Then watch that gap as I tighten things down -- if things move out of alignment, I'll re-do and this time try to compensate for movement while tightening.

One trick is to shove a business card in either side of the caliper between the disk and pads, grab the lever, and then tighten them down.

Disk calipers have in/out adjustments for the pads -- sometimes, there's not enough throw at the lever and simply adjusting the pads out will keep them off the disk. Some mechanical brakes allow for adjustment for both sides, many include pad adjustment on one side only and you are back to playing with lateral adjustment to center them on the other side.

Or the disk is bent slightly. You could use an adjustable crescent wrench to tune it a bit...

Hydraulics are a whole other different issue...

Properly adjusted disk brakes should not make noise when not applied. But the world conspires otherwise.
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Old 05-15-14, 12:42 PM   #19
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So, a faint rubbing sound when the wheel is spinning freely is natural?
No.
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Old 05-15-14, 12:48 PM   #20
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Cable operated, or hydraulic disc brakes?

Setting up disk brakes is a bit tricky, and even having worked on hundreds, it is still not one of my favorite jobs. The how-to vids say loosen the lateral adjustment bolts, squeeze the brake lever to center the caliper, tighten the bolts and your brakes will now be perfectly aligned and noise free.

BS.
My experience is far more limited, I've adjusted the hydraulic disc brakes on my MTB a few times.

What I've done is loosen the block, squeeze the brake lever hard, then tighten the block while keeping the brake lever squeezed. The last time I had issues with the brake rubbing that worked, at least for 20 miles or so and if needs be I repeated it (the problem had appeared part way through a long ride). A lot of the time if I was aware the brakes were rubbing a little I just gave the brake lever a quick squeeze and the problem went away for a few miles. Then the problem just went away for no readily apparent reason.

There's not much clearance between the pads and the rotor so it doesn't take much getting into the works to make them scrape. Likewise you don't need much distortion in the rotor to make it rub somewhere or other.
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Old 05-15-14, 12:57 PM   #21
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My experience is far more limited, I've adjusted the hydraulic disc brakes on my MTB a few times.

What I've done is loosen the block, squeeze the brake lever hard, then tighten the block while keeping the brake lever squeezed. The last time I had issues with the brake rubbing that worked, at least for 20 miles or so and if needs be I repeated it (the problem had appeared part way through a long ride). A lot of the time if I was aware the brakes were rubbing a little I just gave the brake lever a quick squeeze and the problem went away for a few miles. Then the problem just went away for no readily apparent reason.

There's not much clearance between the pads and the rotor so it doesn't take much getting into the works to make them scrape. Likewise you don't need much distortion in the rotor to make it rub somewhere or other.
That's the technique which is supposed to work and good on you if it does. On new assemblies, sometimes it works, usually with Shimano hydraulic brakes, sometimes it doesn't, like with many lower-end mechanical brakes.

And yes, sometimes a quick squeeze can even things out and get a rider back to silent running brakes -- done that trick myself on occasion. Another head scratcher is when things are silent in the stand or riding upright, but cornering will induce noise.

Clearance is indeed tight and it does not take much at all to get off by a little bit to the point where there is noise. The most typical is a tsing, tsing, tsing noise indicating that the disk is warped somewhere. That's when the adjustable wrench comes out for some truing -- again, I sight down between the pad and disk and see where it's hitting, then bend the disk with the wrench appropriately. Small, gentle movements here is good, but metal disks are a bit springy, so be prepared to spend some time getting a disk trued up...
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