Tire Resistance?

This, like many other things real and cycling, isn't easy. I would be
pleased to 'tell' the answer but it would just engender a trolling contest.
May I respectfully suggest a return to school, starting with college
freshman-level calculus-based physics?

"Duram" <danur@@ig.com.br> wrote in message
news:[email hidden]...

Quoted message said:

3 tires has more, less or equal total ground resistance than 2 tires?
contact area is 3 times more but weight in each tire is 1/3 times less,
how to figure?

On Fri, 19 Nov 2004 18:44:36 -0200, "Duram" <danur@@ig.com.br> wrote
in message <[email hidden]>:

Quoted message said:

3 tires has more, less or equal total ground resistance than 2 tires?

Yes. Definitely.

Guy
--
May contain traces of irony. Contents liable to settle after posting.
http://www.chapmancentral.co.uk

88% of helmet statistics are made up, 65% of them at Washington University

Quoted message said:

3 tires has more, less or equal total ground resistance than 2 tires?
contact area is 3 times more but weight in each tire is 1/3 times less,
how to figure?

On loose gravel or snow three-wheel vehicles use three tracks, while
two-wheelers use only one. Two-wheel usually is better in this case.

Duram' danur@@ig.com.br said:

3 tires has more, less or equal total ground resistance than 2 tires?
contact area is 3 times more but weight in each tire is 1/3 times
less, how to figure?

(I am not an Engineer) I guess you are talking about what cyclists
usually call "rolling resistance" which is caused by the energy loss due
to tyre distortion.

I think the total is the same whatever the number of wheels: I think it
may depend on the linearity of the weight/tyre vs. resistance curve.

--
Simon Kellett, Darmstadt, Germany | http://home.arcor.de/zoxed
Hase Kettwiesel trike | ex-Pashley PDQ SWB
Flux V220 CLWB | Zox20 Lowracer

Duram said:

3 tires has more, less or equal total ground resistance than 2 tires?
contact area is 3 times more but weight in each tire is 1/3 times
less, how to figure?

All other things being equal, which of course they very rarely are, I should
imagine the three-wheeler to have slightly higher rolling resistance than
the two-wheeler. The reasoning behind this being:

I had always been under the impression that rolling resistance increased
with the *circumference* of the contact patch, this being why fat tyres
perform well in rolling resistance tests - the fatter the tyre, the closer
to a circle the contact patch becomes and therefore the less the
circumference. This being so, if we have a quad, a trike and a bike, each
of which has a total contact area of 1 square Thingie, and make the odd
simplifying assumption, viz:

a. The area of all contact patches is equal (equal weight on each wheel),
and
b. Each contact patch is a circle

for a bike, the radius r of the contact patch = square root of (pi/2) or
approximately 1.25 Thingies

for the trike, it's the square root of (pi/3), or approximately 1.02
Thingies

for the quad, square root of (pi/4), approximately 0.886 Thingies

The bike has two contact patches, the total circumference of which is
therefore 2*(2*pi*r); approximately 15.75 Thingies

The trike has three patches with a total circumference of 3*(2*pi*r), which
come to 19.3 Thingies

The quad has four patches with a total circumference of 4*(2*pi*r) = 22.3
Thingies. Half as much again as the bike, so we might expect the rolling
resistance to be half as much again as the bike too.

I suspect that things are not *quite* this clear-cut, as:

a. the contact patch is nearer to an ellipse than a circle, and
b. rolling resistance is doubtless affected by other factors as well

but we're still waiting for a nice man to do all the hard sums for us...

--

Dave Larrington - http://www.legslarry.beerdrinkers.co.uk/
World Domination?
Just find a world that's into that kind of thing, then chain to the
floor and walk up and down on it in high heels. (Mr. Sunshine)