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Mechanical Disc Brakes

Old 07-27-14, 08:29 PM
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jpr9845
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Mechanical Disc Brakes

I just purchased a 2014 Diamondback dual sport Trace which came with mechanical disc brakes. I am new to disc brakes and want to find out what, if any, sound should I hear when I apply the brakes.
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Old 07-27-14, 08:56 PM
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Ideally, none.

But for some combination of rotors and pads, screeching - especially during hard braking, is common until the components have properly bedded in.
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Old 07-27-14, 10:10 PM
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try bedding in your brakes.
I do it on a steep hill.
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Old 07-27-14, 10:12 PM
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If those are Tektros, they will be decently quiet when dry and shriek like a witch boiling in oil when they get wet or dirty.
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Old 07-28-14, 07:03 AM
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They may screetch from time to time, but remember you are not destroying your rims in the long run.
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Old 07-28-14, 08:09 AM
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Its the dirt and contamination that starts making noises , clean disc and Pads reduces this ..

Your LBS should be able to demonstrate what they do to service mechanical disc brakes.
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Old 07-28-14, 08:30 AM
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I had to giggle at the Tektro comment!

I recently checked over a Tektro that was giving trouble and found the "innards" full of rust. Cleaned and reassembled with waterproof grease. Works VERY well now.

As already noted, the brakes should make no noise. If you have really good ears you might hear a whirring sound as the slots in the disk pass over the caliper.

-SP
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Old 07-28-14, 11:19 AM
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Thank you everyone for the input. My bike currently has about a half a mile on it, so I will wait until I put some distance on it. Right now when I apply the brakes I hear like a scraping sound and was surprised to hear anything at all. Back to work today so I will have some mileage on it by tomorrow.

Again, thanx!

I happen to work in a 6 floor parking garage, so I will have plenty of smooth downhill area to bed in these brakes!

Last edited by jpr9845; 07-28-14 at 11:29 AM. Reason: More info
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Old 07-29-14, 03:03 PM
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True silence isn't possible, all that kinetic energy of the bike has to go somewhere. You will hear the pads scraping but that should be it. Oh and it shouldn't sound like gravel on a chalkboard scraping.
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Old 07-30-14, 06:24 AM
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Originally Posted by rydabent View Post
... remember you are not destroying your rims in the long run.
Because rims were formed in the fires of Mt. Doom and they are precious to you?
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Old 07-30-14, 06:42 AM
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Originally Posted by cyccommute View Post
Because rims were formed in the fires of Mt. Doom and they are precious to you?
Exactly. And if you put them around your neck, you turn invisible.
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Old 07-30-14, 10:14 AM
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cycc

I am a big booster of disc brakes. Rim brakes in the long run destroy rims. Bikes with disc brakes can have rims designed with both strength and aero considerations in mind. When a rim breaks because of wear down, not only are you on foot, but also you have to buy a new rim, most people have to have a shop rebuild the the wheel. And lastly disc brakes have superior stopping power in the wet, and the mud.
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Old 07-30-14, 10:25 AM
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Skipping the pro-disc brakes rants and trying to answer the OP's question, disc brakes normally make a metal on metal hiss or squeal. If you've ever heard the brakes on trains it's sort of similar (not as loud). Dirt or contamination will make the sound more scratchy, like sandpaper on metal.

New brakes often need seating to reach optimal performance. Seating involves a few hard brakings from medium speed. (don't apply the front hard enough to do an endo, though I believe that every rider needs to experiment and find the threshold of max braking before endo).

The best insicator of the brakes performance is the appearance of the disc. When all is perfect, the brake shoes leave the disc smooth and polished. Embedded sand and grit, causes circular scoring, and means not only poorer brake performance, but faster disc wear. Often mild grit issues clear by themselves with some wear, but if there's serious scoring and the grit sound doesn't clear or improve, you need to clean the pucks.
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Old 07-30-14, 01:39 PM
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Originally Posted by rydabent View Post
cycc

I am a big booster of disc brakes. Rim brakes in the long run destroy rims. Bikes with disc brakes can have rims designed with both strength and aero considerations in mind. When a rim breaks because of wear down, not only are you on foot, but also you have to buy a new rim, most people have to have a shop rebuild the the wheel. And lastly disc brakes have superior stopping power in the wet, and the mud.
I know you are a booster of disc. While rim brakes can wear out a rim, it's not a frequent occurrence in my experience (30+ years) nor is replacing a rim all that onerous. I've broken and damaged many more rims from causes that have nothing to do with brake wear. I see tons of old bicycles at my local co-op that are up to 30 years old that are equipped with the original wheels and original rims. I can't recall having seen more than a few wheels come through the co-op that had a worn out brake track so I'm not the only person that doesn't wear rims.

As for the alleged "superiority" of a disc brake in wet, mud and ice, I have several disc brake equipped bikes. They don't stop any better in rain than my rim brake equipped bikes because the stopping isn't done by the brakes but by the rubber of the tire. In wet, muddy or icy conditions, the grip of the tire isn't any greater than when using a disc or a rim brake. Wet disc brakes have the same lag while the rotor clears as a rim brake does.

And, to jpr9845, disc brakes can squeal. Some brands are worse than others. Contamination can even good systems squeal.
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Old 07-31-14, 08:20 AM
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Originally Posted by rydabent View Post
cycc

I am a big booster of disc brakes. Rim brakes in the long run destroy rims. Bikes with disc brakes can have rims designed with both strength and aero considerations in mind. When a rim breaks because of wear down, not only are you on foot, but also you have to buy a new rim, most people have to have a shop rebuild the the wheel. And lastly disc brakes have superior stopping power in the wet, and the mud.
Well- the OP's question has been adequately answered so let's have some fun with the "disc brake rant."

Brake track wear is really a non-issue. There are conditions that accelerate the wear, but you will experience problems in a disc setup in those conditions as well. Brake track wear can be minimized with proper maintenance and parts selection.

Actually, a rim brake is a disc brake. The rim is just a bigger rotor. We all know that increasing rotor size provides better braking performance.

So Rydabent- if discs are the answer, and they will do for bicycles what they did for automobiles... why are you running mechanicals rather than hydraulics? Mechanical brakes were phased out in cars way back when- probably before you and I were born. Ford in '39 for example. So... go hydraulic if you really want to be the advocate for the latest and greatest.
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Old 07-31-14, 09:25 AM
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My mtb discs always make some sort of sound when applied. Usually it's just a slight hissing sound, but squeals or squawks are not uncommon. In general, I've found discs to be much more problematic than rim brakes. They do have some performance benefits, but for me, they don't outweigh the disadvantages in road use.
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Old 07-31-14, 09:47 AM
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rydabent gets a lot of grief on here for frequently stating his fondness of disc brakes primarily because they don't destroy rims......rydabent, I take it you ride a recumbent (?). Recumbents come in many shapes and sizes, but the wheels on a recumbent are usually smaller in diameter than the common sizes used on other bicycles. If that's what rydabent is riding, the importance of not having brake track wear on much smaller diameter rims is a big deal.

I've got quite a bit of experience with customers who ride Bike Friday touring bikes, and put huge mileage on them. These bikes use 20" wheels, and rim brakes. I've rebuilt a few of these wheels for these customers based on extensive rim wear. Because there simply is so much less brake track (linearly speaking) on a very small rim like that, the brake wear on the rims is GREATLY increased. In a nutshell, riders who use smaller diameter wheels with rim brakes, and put in big mileage, will indeed wear out their rims fairly regularly because of the brake track wear.

Just some perspective.
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Old 07-31-14, 07:08 PM
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well

My LWB bent has rim brakes. My new trike has disc brakes.

As far as hydraulic vs mechanical, I side with mechanical because of the simplicity. Saying cars went to hydraulic is of course true. But even a small car weighs 2500 pounds or more and has power brakes, where a bike and rider weight maybe 200 pounds.

Some one said that if a wheel has to be rebuilt or replaced do to rim wear is no big deal. I would probable consider the cost of the rim and the rebuild a big deal.

Lastly long distance riders DO have rim wear and failure do to grit and riding in the rain. When bike has a broken rim you are on foot!!!! A bike with a broken disc brake can still be ridden using the other disc brake.
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Old 07-31-14, 08:34 PM
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Originally Posted by rydabent View Post



Some one said that if a wheel has to be rebuilt or replaced do to rim wear is no big deal.
Who said that?
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Old 07-31-14, 11:04 PM
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My biggest plug for disc brakes in general: not having to undo the damn caliper every time you take the wheel off.
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Old 08-01-14, 05:53 AM
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Originally Posted by well biked View Post
Who said that?
I said that replacing a rim wasn't all that onerous which is different from saying that "it's no big deal". I also said that I've had to replace more rims due to damage unrelated to brake track wear. Those replacements aren't all that onerous as well. The cost of the rim and the time taken to replace the rim or wheel are equivalent in both cases.
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Old 08-01-14, 07:15 AM
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Additionally where if a rim wears out, a new rim has to be bought, and the wheel has to be rebuilt. I would venture that even among posters here few can lace and tension a wheel properly. But--------there is no big deal to replacing a disc or installing pads in disc brake calipers. I would think the ave poster here can do that himself.

And again and the biggest plus for disc brakes is the fact is if a rim cracks, you are on foot. But with disc brakes you can continue to ride with the remaining disc.
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Old 08-01-14, 08:18 AM
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Rydabent, I'm not sure if you got my point from my earlier post or not, but what I was saying is that as a recumbent rider, presumably with smaller diameter wheels, your concerns about brake track wear on rims are valid, but they're also skewed. With a 20" wheel, for example, you will wear out a rim due to brake track wear several times faster than with, say, a 700c rim. I was hoping I could point this out so that some of the posters in the thread, including you, would consider others' perspectives................When we see a 20" wheel on a Bike Friday come in that's got a seriously concaved brake track, we almost always, among ourselves, comment that disc brakes on these bikes would be a good idea. That's not a very common scenario with a "full size" wheel. We see it, but it's not the chronic problem that high mileage riders with smaller wheels are faced with if they're using rim brakes.
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Old 08-01-14, 08:28 AM
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Originally Posted by eicca View Post
My biggest plug for disc brakes in general: not having to undo the damn caliper every time you take the wheel off.
You haven't discovered the quick release lever? "Undoing" the caliper take maybe two seconds if you are slow and deliberate. Reinstalling a disc wheel requires care to assure the disc is aligned with the caliper opening and takes longer than flipping a qr on caliper brakes or disconnecting/connecting the noodle on V-brakes.
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Old 08-01-14, 08:31 AM
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Originally Posted by HillRider View Post
You haven't discovered the quick release lever? "Undoing" the caliper take maybe two seconds if you are slow and deliberate. Reinstalling a disc wheel requires care to assure the disc is aligned with the caliper opening and takes longer than flipping a qr on caliper brakes or disconnecting/connecting the noodle on V-brakes.
Which is why disc brake bikes should all have through axles.......to do otherwise is a design shortcut.
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