On 16/3/19 7:38 pm, John B. Slocomb wrote:
On Sat, 16 Mar 2019 18:57:21 +1100, James
wrote:

On 16/3/19 10:32 am, John B. Slocomb wrote:


It comes to mind that as the braking resistance is applied at the
contact of the tire and the road and that the resistance is applied to
the wheel hub that a much stronger disc brake wheel would be required
than when using a rim brake as the ratio between the disc brake disc
and the contact with the road is approximately 26.5"/7.5" (average 2
sizes of disc rotor) = about 3.5 ratio while a rim brake is only about
an inch and a half difference so say 26.5/23.5=1.1 ratio. Based on
braking forces it would appear that a disc brake wheel would have to
be roughly 3 times stronger than a rim brake wheel.

36 spoke, cross three, wheels anyone?

But of course an ATB is already so heavy that the addition of strong
wheels is rather a matter of bringing coals to Newcastle.


Well, you don't build a disc brake wheel with radial spokes.

But they do built a rim brake wheel with radial spokes }-)

Yes, I use some I built. It's mostly a fashion thing. The weight
reduction by shorter spokes isn't worth worrying about.

In most cases a regular 3x spoke wheel is sufficient to transfer brake
forces from the hub to the rim.

Imagine the possible force on spokes possible from a 28 tooth chain ring
to a 34 tooth rear sprocket?


I think that if I were riding around in the mud and mire I probably
would want discs but I don't do that. Anywhere that I want to go has
paved roads leading to it.

I find it rather revealing that in 1880 the League of American
Wheelmen, a bicycle advocate group, was formed and one of the first
things that they lobbied for was smooth roads. Now that smooth roads,
in the U.S. at least, probably make up the majority of the roads
people have discovered riding out in the bush where there hardly
aren't any roads at all.


Where I live there are hundreds of kms of gravel roads that are too
rough for my road bike (I've tried). Where as my options are limited by
bitumen only roads. Only the main connecting roads are bitumen, and
they are high speed roads where drivers dislike passing cyclists safely.

I think that people have realised that there are many unmade roads to
explore, and there are few cars on them to worry about.

--
JS