Re: Disk Brakes vs. V Brakes??

treynolds@[EMAIL PROTECTED]
 wrote:
> jim beam wrote:
> > Chris_MdR@[EMAIL PROTECTED]
 wrote:
> > > Hi,
> > >
> > >  - After playing with the brakes for a few minutes, I noticed that
the
> > > discs get noticeably warm, around 170F. Are there ever heating
issues
> > > with disc brakes on longer downhill segments? Seems a stupid
question,
> > > but they did get quite warm just by playing around on level ground
for
> > > about ten minutes.
> >
> > they get warm because of the friction - that's what all brakes do.
> > you'll have no problem with heating issues on a disk braked bike -
once
> > set up correctly, use with complete confidence.
> >
>
> Regarding the heating issue, I came across a couple on a tandem who had
> a hydraulic disk brake in back, instead of a drag brake.  They said
> that on long downhills the brake heating transfers heat to the fluid,
> the fluid expands and they end up with the brake applied without any
> lever action.  They have to stop and let the fluid cool.
>
> A tandem drag brake and a downhill ATB are not the exact same situation
> but both can expect to sometimes apply the brake for 20-30 minutes on a
> very long downhill.  Does this ever occur on an ATB?
>

I've never had heat cause the brakes to apply through heat expansion.
What I do experience is dot4 brake fluid boiling (or the water in the
fluid boiling) and I loose all braking power. And I have to wait until
it cools before continuing down hill. On the same hill with v-brakes I
had a front tire blow because the rim got too hot.

My make of disk brake is not compatible with dot5 fluid, which if I
could use it, would help.

Here's a question, which action produces the most heat, keeping the
brakes on to control speed on a steep hill or letting the bike go and
then jamming on the brakes at the last second to kill the speed?
Laters,

Marz

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