On Mon, Mar 31, 2008 at 6:33 PM, Jan Heine <heine94@earthlink.net> wrote:
> At 5:00 PM -0700 3/31/08, John Barry wrote:
> >Sounds like another shot-from-the-hip Jobst theory.
> >
> >Anyone who has driven on good tires on a wet road, and
> >then driven on bald ones on a wet road and not noticed
> >a difference, would have to be either very distracted,
> >or borderline comatose.
> >
> >Hydroplaning is a very real phenomenon,
>
> In cars, hydroplaning is a real problem, because the contact patch is
> very large. (Car tires run at low pressures compared to bicycle
> tires.) A bicycle's contact patch is too small to hydroplane.
> (Semi-trucks also have much less of an issue with hydroplaning, as
> they are so heavy.)
>
> So it is safe to say that hydroplaning is not an issue with bicycles.
>
> However, I have noticed that bald bicycle tires do appear to slip
> more easily on some wet roads. For example, the latest Avocet tires
> are terrible in the wet. This could be due to the rubber compound,
> but I suspect something else is at work here:
Remember there is also profile to consider.
I have not noticed anything in regards to the newer Avocet tires.
>
> Roads are most slippery when it has not rained in a while, and there
> is a film of oil/dust/grime on the surface. Once a few days of
> vigorous rain have washed the roads clear, traction is much improved.
>
> Now, could a bicycle tire with a fine tread cut through that very
> thin layer of grime/dust/oil and find traction where a bald tire
> would ride on top and slip?
No, if a filre tread is stiff enough to "cut" through, it would also be
stiff enough to ride on and prevent the voids from making contact. This in
itself would cause less traction.
>
> Jobst et al., who say that bicycle do not hydroplane, are correct.
> However, their conclusion that tread does not make a difference may
> be wrong... because as so often, they look at the wrong problem.
I believe they are saying (and was the origional argument) is that tread is
not beneficial.
I don't think they are saying tread does not make a difference.
>
> I am thinking of a way to test this hypothesis. Obviously, we'd have
> to test the same type of tire, one with new tread, the other with the
> tread worn/sanded off. But how do we test without risking life and
> limb?
Avocet had (had) such a device. And you wouldn't want to test a new treaded
tire with a worn one.
You would test two new tires. One with xx tread pattern and a one with a
"slick" or treadless design.
>
> In the mean time, I see no harm done in a fine file tread - and it
> looks nice, too - so I am going with that for now.
There really isn't any harm, but when we're splitting hairs, a treadless
will win. And when I am shooting down Page Mill Rd
in the rain. My hair-splitting will side with treadless, hands down.
>
>
> (The best tire may be a somewhat worn one, with less tread in the
> center, and more on the edges. So you get better traction when
> cornering than on the straights.)
That's is false! You do not get better traction from having a file pattern on your tire!. You have *less* contact with the road! This has all been tested by Avocet, Specialized, Michellin etc...
>
> Jan Heine
> Editor
> Bicycle Quarterly
> 140 Lakeside Ave #C
> Seattle WA 98122
> http://www.bikequarterly.com
> --
> _______________________________________________
>
--
Mike Scammon
Menlo Park, Ca.