Ryan Cousineau wrote:
> In article <
[email protected]>, "Matt O'Toole"
> <
[email protected]> wrote:
>
>
>><
[email protected]> wrote in message
news:aN%[email protected]...
>>
>>
>>>The big negative for disc brakes is the failure mode and
>>
>>reliability
>>
>>>when descending something like passes in the Alps where
>>
>>missing a
>>
>>>hairpin turn is DEATH. It's a long way down. When you
>>
>>lose fluid or
>>
>>>get even a tiny leak, it is serious trouble.
>>
>>You don't even need a leak to have major brake failure with disks. The main problem, safety-wise,
>>is that they can overheat and "go away" very suddenly. Rim brakes' fade is much more gradual, and
>>when it does happen you still have some braking power left.
>>
>>Rim brakes also cool off a lot faster -- usually in seconds. Disks get hotter and hotter, and may
>>take several minutes to cool down. And it's not just the rotors and pads that get hot, but the
>>calipers, oil, etc.
>>
>>Matt O.
>
>
> Goodness, all these dangerous discs! I'm glad nothing important like my car or motorcycle uses
> these deadly brake types.
>
> PS: was I away when most bicycles stopped having two completely independent braking systems? Has
> anyone here ever experienced complete brake failure, except maybe "I was riding a track bike
> with no front brake, and..."?
>
I had instant rear brake failure with rim brakes when the retaining pin fell out (don't as me how,
but it did), and the rear brake pad was loosened by a slight pull back while I was stopped and the
brakes were on, then I took off down a fireroad. A downhill fire road. Only thing I got from the
rear was some awful metal-metal squealing.
Let me tell you, it doesn't matter if you have hydraulic or cables, if they break, or malfunction,
you're not going to have "some" break left - you won't have anything.
I've NEVER heard of hydraulic discs overheating so badly they completely went away. And don't tell
me braking power is a factor of how much heat they can dissipate - if you're heating up the disc,
its through friction. It doesn't matter where that heat goes, its still kinetic energy being
converted into heat. Disc brakes are designed to work at much higher temperatures than rim brakes,
and for good reason. Obviously, the smaller metal disc is going to heat up more, but excess heat
there really isn't going to cause any huge problems. Hydraulic systems accomodate for the heating of
the hydraulic fluid, or you can just use alittle less pressure on the levers. Every part of the
system is designed to take the higher heat levels, so heat really isn't too much of an issue. As
long as the pads can take it, the brake will still work fine (if not better, if designed that way.
If you've ever driven a car with drum brakes and compared it to a car with disc brakes, or a
motorcycle for that matter, then you'll see that the discs handle the heat just fine where some
other systems don't).
Jon Bond
