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  1. #1
    Senior Member rydabent's Avatar
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    Wouldn't it be smart for all bike mfg to go to disc brakes

    If bike mfg went to disc brakes it would seem to me to be a huge improvement. Discs work better in the wet, and the biggest thing of all is your rim doesnt get ruined. Add to that the rim could be of any shape the rim mfg thot best.

    I have read many cross country ride reports where rims have failed due to wear out. But if these riders had disc brakes, if they had brake trouble just changing either the pads or both disc and pad would fix the problem at a much lower cost.

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    Rim brakes are cheaper for the bike manufacturers; your cost to replace worn-out rims is of little concern to them. They are also lighter so they can advertise a lighter bike and probably present fewer warranty costs to them.

    The corporate bean counters are concerned with the bottom line, not you.

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    The Recumbent Quant cplager's Avatar
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    Hi,

    I think it depends a lot on what type of riding you are doing. That being said, I do hope to see disc brakes become options on many more bikes.

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    I'm thinking about disc brakes myself lately. I've read opinions that they can be finnicky (always seem to be rubbing, etc) but I don't own any. I've kind considered them as "only needed for extreme down hill situations" which is not typical (especially around here). I'd be concerned about simple maintenance on the road. I want to be able to fix anything while on a long trip. I don't think I see disc brakes on randoneuring bikes or long distance touring builds as much as I see canti brakes. I would be interested in other's opinions about maintainability and reliability over long distance rides.
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  5. #5
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    Disc brakes are:
    -Heaver
    -More expensive.
    -Complicate wheel removal/installation particularly if you have to change a road-side flat tire.
    -Require a stronger (read heavier) fork and reenforced rear stays.
    -Hydraulic versions are prone to fade from excess heat on long downhills. (more of a problem for road bikes than MTB use).
    -Require proprietary pads that are more expensive and more difficult to find.
    -More sensitive to minor mis-alignment

    They do have improved wet braking although good double pivot rim brakes with good pads aren't far behind. Your point about lack of rim damage is valid but only on bikes used routinely in bad weather or in harsh off-road conditions. On road bikes used in mostly fair weather I have rims with well over 25,000 miles still in good condition. The argument that disc-only rims could be significantly lighter isn't valid. Rims are designed for adequate strength and rigidity and the additional material added for brake track wear is minor.

    So, for MTB, Cyclocross and all-weather commuter bikes, perhaps disc's advantages do out weight their several disadvantages. But the desirability of their universal application is far from obvious.

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    Senior Member cale's Avatar
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    Quote Originally Posted by dsbrantjr View Post
    Rim brakes are cheaper for the bike manufacturers; your cost to replace worn-out rims is of little concern to them. They are also lighter so they can advertise a lighter bike and probably present fewer warranty costs to them.

    The corporate bean counters are concerned with the bottom line, not you.
    I agree, up to a point. I think the price could be justified but probably only on those brands that sell to people that value disc brake benefits. That's a tough sell to casual bikers, and the vast majority of buyers.

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    "Wouldnt it be smart for all bike mfg to go to disc brakes"

    In a word....No.

  8. #8
    Senior Member chriskmurray's Avatar
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    You do realize how few people buying a bike will ever ride it enough to wear out rims right? It is already hard enough to get the casual cyclist to spring for a bike shop quality bike, upping the cost even more would be counter productive. Many people buying bikes only ride in the dry and rarely on hills, v-brakes are more than sufficient.

    Also, I dare you to go to the touring section and tell them we should do away with rim brakes entirely. Rim brakes still have some advantages other than cost and weight, mostly for touring cyclist you can find replacement wheels much easier and you can find replacement pads in any country, which may not always be the case for discs.

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    +1000 on Hillriders comments.

    I'm considering discs for my next commuter bike which is ridden on heavy traffic on city streets rain or shine, but there's no way I feel they're needed or better for my road or touring bikes.

    Yes I ride in all weather, and rim braking in the rain isn't great, but it's no issue on the open road. Neither is rim wear an issue, I use tubular rims with a total wall thickness of 0.7mm and in 45+ years of riding I've never had any issues of excess rim wear.

    Since my total wall thickness is less that the allowable wear of clincher rims, this can't be an issue for most roar riders either.

    Disc brakes do offer better rain performance, but they make for a heavier, more expensive to buy and maintain system. They also increase stress on the fork, so unless they're needed, they're more of a disadvantage than benefit.
    Last edited by FBinNY; 10-26-12 at 08:58 AM.
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  10. #10
    Mad bike riding scientist cyccommute's Avatar
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    HillRider is correct in almost everything he says. The only point I would have minor issues with is the complication of wheel removal. I don't find hub mounted discs wheels any more difficult to remove or install than rim brake wheels.

    I live where it is dry most of the year so I don't get that much opportunity to test wet weather braking but I have done it, most recently on a 40 mph downhill off New Found Gap in the Great Smoky Mountains. My cantilever brakes performed the task without issue and at no point...even in a driving rain...did I feel like my brakes were inadequate. Equipment is only part of braking. Knowing how to use them is another...more important...part of braking. Knowing how to apply the brakes and how to move your body to get the most out of your brake is far more important than the kind of brakes you have.
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  11. #11
    Senior Member cale's Avatar
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    Quote Originally Posted by HillRider View Post
    Disc brakes are:
    -Heaver
    -More expensive.
    -Complicate wheel removal/installation particularly if you have to change a road-side flat tire.
    -Require a stronger (read heavier) fork and reenforced rear stays.
    -Hydraulic versions are prone to fade from excess heat on long downhills. (more of a problem for road bikes than MTB use).
    -Require proprietary pads that are more expensive and more difficult to find.
    -More sensitive to minor mis-alignment

    They do have improved wet braking although good double pivot rim brakes with good pads aren't far behind. Your point about lack of rim damage is valid but only on bikes used routinely in bad weather or in harsh off-road conditions. On road bikes used in mostly fair weather I have rims with well over 25,000 miles still in good condition. The argument that disc-only rims could be significantly lighter isn't valid. Rims are designed for adequate strength and rigidity and the additional material added for brake track wear is minor.

    So, for MTB, Cyclocross and all-weather commuter bikes, perhaps disc's advantages do out weight their several disadvantages. But the desirability of their universal application is far from obvious.
    Heavier - but gram counting is meaningless in the absence of a superior alternative.
    More expensive - compared to what? Campy components? I don't agree.
    Complicated wheel installation /removal? I haven't found this to be true. No more complicated than remembering to keep the quick release lever on the left. Less complicated the more "out-of-true" the wheel.
    Heavier frame construction - Only racers need apply for this argument.
    Fade prone - overheated rims are also a problem on long downhills.
    Require proprietary pads - Aftermarket pads are sold for the most popular models. For example, at least three disc pad manufacturers sell pads for the popular Avid BB7 model brakes in addition to Avid, the manufacturer.
    Misalignment issues - no more so than rim brakes.

  12. #12
    Senior Member Retro Grouch's Avatar
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    Complicate wheel removal and reinstallation? I certainly haven't found that to be true.

    Also hydraulic brake fade from heat buildup? This is the first that I've ever heard of that one. I have heard of hydraulic disc brakes locking up from heat expanding the brake fluid in a closed system.

    I'm a non-believer in manufacturers' conspiracies. If manufacturers believe a significant body of buyers is demanding disc brakes, they'll offer bikes with disc brakes - and the corporate bean counters will be leading the push.

  13. #13
    Senior Member epiking's Avatar
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    Interesting discussion, braking power needs versus dynamic mass. I have no experience with disc brakes, although think about on the rare occasion I ride in off weather. I guess it boils down to the needs of your particular ride/style.
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  14. #14
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    Quote Originally Posted by Retro Grouch View Post
    Also hydraulic brake fade from heat buildup? This is the first that I've ever heard of that one. I have heard of hydraulic disc brakes locking up from heat expanding the brake fluid in a closed system.
    I've read reliable reports of heat buildup "boiling" the brake fluid and causing a loss of brakes on road bike applications.

    As to alignment problems, there have been dozens of threads on this forum from posters having difficulty aligning and keeping discs aligned. Misalignment with rim brakes, particularly dual pivot and V-brakes is very easily rectified. It's not nearly as easy with disc brakes for the mechanically inexpert.

    As to cale's comments: Dismissing the weight issues is absurd. Not only racers are concerned (maybe overly concerned) with weight but many regular riders obsess over it too. As expensive compaired to what? Campy isn't the benchmark for cost, mid-line Shimano and SRAM are.

  15. #15
    Senior Member cale's Avatar
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    Quote Originally Posted by HillRider View Post
    I've read reliable reports of heat buildup "boiling" the brake fluid and causing a loss of brakes on road bike applications.

    As to alignment problems, there have been dozens of threads on this forum from posters having difficulty aligning and keeping discs aligned. Misalignment with rim brakes, particularly dual pivot and V-brakes is very easily rectified. It's not nearly as easy with disc brakes for the mechanically inexpert.

    As to cale's comments: Dismissing the weight issues is absurd. Not only racers are concerned (maybe overly concerned) with weight but many regular riders obsess over it too. As expensive compaired to what? Campy isn't the benchmark for cost, mid-line Shimano and SRAM are.
    I love opinions that are stated as though they are facts. You can't prove that you're right and I'm wrong so you attacked the post as absurd, another opinion. My guess, is that the proportion of riders "obsessing" over weight is tiny compared to the proportion that would argue that better braking performance, in all circumstances, is worth a small weight penalty.
    Last edited by cale; 10-26-12 at 10:24 AM.

  16. #16
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    you would have to really heat the fluid up to get it to boil though.

    i used to race scca solo2 d modified class with a bmw 325i. brake fade is a huge issue with automotive racing so i have experienced it but on a bicycle? i have a hard time believing people riding would have brake fluid overheating problems unless they are out riding mountains and all of it being down hill riding.

    brake fade is caused by the pads overheating though, not hte fluid overheating. when your pads heat up, they produce more of a gas then normal. this gas gets trapped between the pad and the disk creating cushion which keeps the pad from clamping hte disk properly. that is why automotive brakes can be bought drilled or slotted, or both. the drilling is not the best way to go but slotted rotor disks allow the grooves to expel the gas from the disk face letting the pads bite again.
    I know nothing, I am just here to learn

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    you would have to really heat the fluid up to get it to boil though.

    i used to race scca solo2 d modified class with a bmw 325i. brake fade is a huge issue with automotive racing so i have experienced it but on a bicycle? i have a hard time believing people riding would have brake fluid overheating problems unless they are out riding mountains and all of it being down hill riding.

    brake fade is caused by the pads overheating though, not hte fluid overheating. when your pads heat up, they produce more of a gas then normal. this gas gets trapped between the pad and the disk creating cushion which keeps the pad from clamping hte disk properly. that is why automotive brakes can be bought drilled or slotted, or both. the drilling is not the best way to go but slotted rotor disks allow the grooves to expel the gas from the disk face letting the pads bite again.


    and i am not saying brake fade doesn't happen, just i have a hard time thinking that would be a problem on a bike versus heating up your normal brake pads
    I know nothing, I am just here to learn

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    my guess, is that the proportion of riders "obsessing" over weight is tiny compared to the proportion that would argue that better braking performance center in all circumstances is worth a small weigh penalty.

    I'd guess the opposite. I don't think most riders are clamoring for better braking performance. Brakes work well enough as it is and more riders are more concerned with going faster than they are with stopping faster. I can see discs becoming standard on other bikes, but I don't think they'll take over on road bikes until everyone riding in the TdF is using them.

  19. #19
    Senior Member Flying Merkel's Avatar
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    I have bikes with coaster brakes, caliper brakes, cantilever brakes, V-brakes, and disc brakes. My real-world typical rider take:

    Coaster brakes are for low speed fun bikes.

    The three different types of rim brakes I have don't seem to differ in stopping power or ease of modulation. Any of these can lock the rear tire in a controllable manner. Set up is easiest with V-brakes. Getting my 1982 vintage Dia-Compe cantis set up properly near drove me to tears & drinking. They work great and haven't had to touch them since. Out of true rims are the biggest headache of rim brakes. Rim brakes are the easiest for wheel removal if there is a quick release in the set up.

    I have a mountain bike with cheap Nashbar mechanical discs. After set-up and wearing in they work very well. You can twist the front wheel out of the drop outs under hard braking if the QR isn't clamped down hard. Wheel removal & replacement is a pain, but a manageable pain. Discs look cool. Putting a rear rack on the bike is now a tricky proposition.

    Brake fade isn't an issue for me. Wish I was that badass of a rider that could fade the brakes. With alloy rims, wet weather braking is good with rim brakes. I clench my teeth when I hear that grinding sound of grit between pad & rim. Sorry if I'm repeating the obvious, but rarefied discussions of theoretical differences is a useless exercise.
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  20. #20
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    Quote Originally Posted by HillRider View Post
    Disc brakes are:
    -Heaver
    -More expensive.
    -Complicate wheel removal/installation particularly if you have to change a road-side flat tire.
    -Require a stronger (read heavier) fork and reenforced rear stays.
    -Hydraulic versions are prone to fade from excess heat on long downhills. (more of a problem for road bikes than MTB use).
    -Require proprietary pads that are more expensive and more difficult to find.
    -More sensitive to minor mis-alignment

    They do have improved wet braking although good double pivot rim brakes with good pads aren't far behind. Your point about lack of rim damage is valid but only on bikes used routinely in bad weather or in harsh off-road conditions. On road bikes used in mostly fair weather I have rims with well over 25,000 miles still in good condition. The argument that disc-only rims could be significantly lighter isn't valid. Rims are designed for adequate strength and rigidity and the additional material added for brake track wear is minor.

    So, for MTB, Cyclocross and all-weather commuter bikes, perhaps disc's advantages do out weight their several disadvantages. But the desirability of their universal application is far from obvious.
    I don't know much as I am fairly new to disc brakes on bicycles, but unless you are physically carrying the bike or racing .. I seriously doubt 2 pounds will make much of a difference and as far as brake fade... brake fade ( as it pertains to automobiles) is where a gas builds up (due to heat) between the brake pad and the rotor causing the brake pads to lose physical contact with the rotor.. as far as I know, brake fade has absolutely nothing to do with brake fluid.

    your points are all valid except for the brake fade only on hydraulic systems and the complexity of tire removal, however most of your points are rather minuscule and appears to just be argumentative against disc brakes

  21. #21
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    Quote Originally Posted by chriskmurray View Post
    ...you can find replacement pads in any country, which may not always be the case for discs.
    OTOH, a matchbox worth of volume will hold something like 4 pairs, which ought to see you across a continent or two before wearing out. Not much of a problem bringing that along.

  22. #22
    coprolite fietsbob's Avatar
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    Also.. (a +1) disc Brakes don't lend them selves to the Fast wheel changes
    that are a part of replacing punctured sew up tires in the big road races ..

    but as a consumer, without that criteria, you may be happy with disc brakes..

    They are making inroads into Cyclocross racing , but at the top levels
    the rider just grabs another whole new clean and ready to go bike
    when they pass their pits on the next lap.


    yea think ahead, bring spare pads... you can find aluminum backed ones ,
    to weigh less than the ones on steel backing.
    Last edited by fietsbob; 10-26-12 at 12:21 PM.

  23. #23
    Retro Grouch onespeedbiker's Avatar
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    There is a lot more to the bicycle market what works over a larger spectrum. First, bicycle R&D starts with race bikes. You may say that is stupid or non-racers don't need ultra light bikes, but the market says otherwise. Selling a race bike with caliper brakes with a lighter frame while lower level bikes are heavier with discs brakes simply will not sell. There is a article in the recent Bicycling mag on the Colnago race bike, the first with disc brakes. First you have to remember that caliper brakes work as well a disc in most conditions on aluminum rims, even in the rain with the proper pads. Further it is more common for road bikes to have long sustained down hills that mtb with discs and the hydraulic oil does not need to boil; the hoter it gets the more power in braking is lost. Once hydraulic oil gets hot it does not cool very fast. This is opposed to aluminum rims that have much more surface area that discs and cool very quickly. The primary purpose for disc brakes is the use of carbon wheels. Carbon wheels have been around for about 10 years (or more) and most the accidents you see in recent crashes are the result; carbon wheels just don't stop well and in rain they don't stop at all! Disc brakes will solve this problem. But the reality of why you won't see disc brakes on most road bikes is simply there is no market for them.

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    Quote Originally Posted by fietsbob View Post
    Also.. (a +1) disc Brakes don't lend them selves to the Fast wheel changes
    that are a part of replacing punctured sew up tires in the big road races ..

    but as a consumer, without that criteria, you may be happy with disc brakes..
    Undo QR, drop wheel, slot in new wheel, go? no brake to unhook/loosen via lever. I fail to see how people have an issue replacing disc wheels, maybe you all run your wheels crooked?

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    Boiling brake fluid can be a problem. It's simply heat transfer from the pads to the fluid, closest to the pad.

    http://www.stoptech.com/technical-su...rs/brake-fluid

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