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  1. #1

    Disk Brakes - Why Front and Rear

    Caliper Rim brakes on road bikes are pretty awful in comparison with just about every other brake type. Cheap hybrids and MTB bikes have far better braking ability. So the move to add disk brakes to road bikes makes a lot of sense to me. But..
    Whether you are in a car, bus, m/bike or road bike and you need to reduce speed fast it is the front brake that does the work. So having a better front brake is essential. But...
    Why do you need a disk brake on the rear of a road bike. I have no problem locking my rear caliper brake in emergency braking (wish it didn't lock), it also works very well as my brake for minor speed corrections and for the last part of coming to a stop.
    Isn't the added technology, gear, etc, a waste on the rear end where the current hub has enough things to cope with?
    Why are the road bike manufacturers and pros trialing front disk and rear caliper?

  2. #2
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    I've wondered the same thing myself. Save some weight and complexity of they were front only.

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    Senior Member coolboarder's Avatar
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    Quote Originally Posted by longinthetooth View Post
    Caliper Rim brakes on road bikes are pretty awful in comparison with just about every other brake type.
    What brakes are you using then LTT? My bikes variously have Campagnolo Chorus/Record, Shimano Dura Ace and SRAM Red and the limiting factor with all of them is the ability of the tyre to grip. I can brake safely even in the wet with Koolstop Salmon blocks.
    It doesn't matter how many times you fall down, its how times many you get back up that count.

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    Quote Originally Posted by longinthetooth View Post
    Caliper Rim brakes on road bikes are pretty awful in comparison with just about every other brake type. Cheap hybrids and MTB bikes have far better braking ability. So the move to add disk brakes to road bikes makes a lot of sense to me. But..
    Whether you are in a car, bus, m/bike or road bike and you need to reduce speed fast it is the front brake that does the work. So having a better front brake is essential. But...
    Why do you need a disk brake on the rear of a road bike. I have no problem locking my rear caliper brake in emergency braking (wish it didn't lock), it also works very well as my brake for minor speed corrections and for the last part of coming to a stop.
    Isn't the added technology, gear, etc, a waste on the rear end where the current hub has enough things to cope with?
    Why are the road bike manufacturers and pros trialing front disk and rear caliper?
    Better quality rim brakes on a decent wheel rim are more than adequate. In fact, the very best rival disc brakes. They have, after all, served us for decades. The latest designs are extremely effective.

    What does "effective" mean? It isn't about whether you can lock the wheel or not, since that's the last thing you want to do. It's much more about the degree of control you can apply. This has two main aspects: how much force is needed at the lever to apply the required force at the calliper; to what degree can the braking forces be modulated?

    Mid and high range rim brakes from the likes of Shimano, SRAM and Campagnolo are very effective in these ways. Equivalent level disc brakes (at similar points in the ranges) are better, especially in terms of modulation (controllability of the braking force applied) - although cable-operated are not much better than rim brake equivalents at the back (see below).

    Since a cable brake at the rear has a longer length of cable and cable housing, as well as more kinks or bends (especially with modern inside-the-frame cable routing) the required braking force at the lever is usually increased. In addition, the drag of cable in outer and around the bends greatly reduces the degree of modulation possible. Back cable brakes feel much more wooden or squidgy than front brakes, whether the calliper is a mechanical disc or a rim brake.

    For this reason, a hydraulically-operated rear disc brake offers far better control - less braking force required at the lever, as well as much more "feel" and ability to modulate the braking. The hydraulics don't have cable-drag and don't care about cable bends.

    Lataxe

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    Senior Member VLAD (the Friendly Vamp)'s Avatar
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    Don't forget to have a good dentist as well for when you go over the bars.
    NOT logging in every and each visit now.
    Going to have to BITE someone soon.
    Amicabili Lamia

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    Good idea actually...

    I can see considerable benefits for discs in the mountains as it keeps the braking temperature away from the rim and tyre on long descents, as well as making for reduced hand grip pressure which can be fatiguing.

    Wouldn't bother otherwise. I cannot think of a single occasion where I have been concerned by my bike's ability to slow or stop, even on a descent of the Stelvio in sleet.
    "Training is also a battle" - Kim Jong-Un

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    Quote Originally Posted by PRSboy View Post
    Good idea actually...

    I can see considerable benefits for discs in the mountains as it keeps the braking temperature away from the rim and tyre on long descents, as well as making for reduced hand grip pressure which can be fatiguing.

    Wouldn't bother otherwise. I cannot think of a single occasion where I have been concerned by my bike's ability to slow or stop, even on a descent of the Stelvio in sleet.
    With you on that one PRS.
    I like the idea of riding carbon rims in the mountains, so I can look cool at the cafe at the top but only with disc brakes. Too fat for long descents on carbon no matter what the adverts say.
    BUT
    I don't like disc brakes, they're too good.

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    Quote Originally Posted by Dan Tungate View Post
    With you on that one PRS.
    BUT
    I don't like disc brakes, they're too good.
    Mr T,

    Is this the doublespeak of which I have read in that dystopian novel by George? "Too good" meaning "not good" aka "poor"?

    Why is that, do you think? Do you man it's too easy to lock the wheel because it takes less lever-grab? Shurely shome mishtake as the lever also tells you a great deal more about what the calliper is doing to those wheels, aka "modulation", meaning one can tell just how much grab will do what.........?

    I feel you must decode your cryptic remark.

    Lataxe, a convert.

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    Senior Member Gasper's Avatar
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    Quote Originally Posted by Lataxe View Post
    Mr T,

    I feel you must decode your cryptic remark.

    Lataxe, a convert.
    If I may butt in, in a split second panic situation I tend to grab the brakes, that could be a problem with the additional stopping power of discs, especially in the dry.
    "Go forth and ride your bike". Courtesy of Me 2015.

  10. #10
    Senior Member coolboarder's Avatar
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    Quote Originally Posted by Gasper View Post
    If I may butt in, in a split second panic situation I tend to grab the brakes, that could be a problem with the additional stopping power of discs, especially in the dry.
    I'd say especially in the wet as the tyre isn't going to grip and you're more likely to skid, I've skidded a few times in the wet with rims brakes locking let alone discs. But re your panic reaction, I think that once you're used to discs you will have learned how to modulate them.

    For now, for me, weight is the most important factor. I'm more interested in going fast uphill than slowly down!
    It doesn't matter how many times you fall down, its how times many you get back up that count.

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