Quoted message said:Pat Lamb said:Quoted message said:> oem campy. best by far. they stop you in the wet too, unlike
> kool-stops.Quoted message said:Quoted message said:Wow. So all those times I hit the brakes in downpours, it was
something other than my Kool-Stop brake shoes that stopped me!Quoted message said:FWIW, my experience says Kool-stop pads take one extra revolution,
given normal brake pressure, to grab when wet. There's a tale
behind that conclusion, of course...Quoted message said:My new bike came with Shimano pads; it took a couple weeks before I
got the Kool-stop pads in, and I wasn't sure I had them installed in
the shoes just right, so I only put one wheel's worth on for a few
months. Now, although I ride some in rain (not as much as Seattle
cyclists), I've only had two stops in the last three years where I
wasn't sure I could stop in time because of water on the brakes.
The worst, repeatable, problem I have with wet braking is when I
wheel the bike through grass wet with heavy dew out to the road. I
usually remember to squeegee them off at the first sign, half a
block away, down a nasty 6 foot drop. That's where I figured out
the rear wheel (with the stock Shimano pads) started grabbing about
one rev before the front wheel, with the Kool-stops.Quoted message said:However, the one time I had wet rims AND there was a car coming, I
grabbed the front brake with some additional authority, and the
Kool-stop pads responded rapidly. I stayed out of the road, the
oncoming car did not hit me, and I managed not to go over the bars.Quoted message said:I've since changed the back brakes to Kool-stops because, as noted
here previously, they don't embed grit in them and start turning
gouges in the rim. I expect the rear rim will smooth out in a few
(thousand) more miles from the Shimano pad abuse.As I mentioned before, here on the forum, water in the film
thicknesses of interest on smooth surfaces is not readily wiped away
so that only when the rim begins to get warm from braking will water
displace from between brake pad and rim. an example of this is a
window squeegee with sharp edged rubber. It glides over a window on
the boundary layer of water that it cannot displace. The same goes
for windshield wipers. Another example where water has an affinity
for surfaces while giving good lubrication occurs when shaving with a
blade.I had the opportunity to test this before the days of Kool-Stop salmon
brake pads and after, with the same results. When snow builds up on
the inner circumference of a rim, there is almost no braking,
regardless of how hard the brake is applied, until all the snow has
melted and no longer acts as water supply for the brake surface. Once
the snow is gone, braking rapidly recovers to normal.I found no perceptible difference between Campagnolo and Kool-Stop
brake pads with this experiment, but I must admit that there was more
than a year between tests. Still, zero braking is not hard to
distinguish from braking.The test also made clear that when braking in rain, the brake track
remains essentially "dry" unless the downpour splashes from the road
onto the rim. In that event, response is poor.
which is precisely my point. when it's /really/ wet, response on
kool-stop pads /is/ poor. abysmally poor.
you're right about boundary layers causing this. the irony is, pads
that can break through this tend to grit up.
on reflection, i think i should qualify my statement about campy pads.
they're very effective, even in horizontal rain, and they're excellent
against grit. but they can /temporarily/ grit. i've found that
brake-release-brake repeatedly allows grit to move on before getting
embedded. old shimano pads catch but don't release.
Quoted message said:
Another interesting characteristic of water is brake squeal that can
be piercing at one time and absent at another. Kool-Stop salmon pads
seem to be more sensitive to atmospheric humidity than some in that
they squeal readily when first applied if they have been worn enough
to make full contact. Once the rim warms, squealing ceases. There
are other reasons for brake squeal, such as riding through a meadow
with rich weed foliage (tar weed) or touching a rim with greasy hands.Jobst Brandt