# Touring Wheels for a Super Galaxy

James Thomson wrote:

> The theory is that a tyre will adopt an arc of roughly constant
> curvature between the beads. The wider the rim, therefore, the larger
> the radius of curvature across a tyre of a given nominal width. The
> vertical compliance (and therefore the comfort) of the tyre is
> related to the rate of change of contact patch area with vertical
> displacement, which increases roughly in proportion to the radius of
> curvature of tyre cross section at a given pressure.

Sorry I don't completely understand that.

Let's simplify things by making the object rectangular in cross section
(or as near to it as we can physically get)......

100 x 40 x 40 cm inflatable cuboid sausage. Lay it on its long side and
bounce up and down on top of it. Now do the same with it sat on its end.
What's the difference?

~PB

"Pete Biggs" <[email protected]> wrote:

> James Thomson wrote:

> > The theory is that a tyre will adopt an arc of roughly constant
> > curvature between the beads. The wider the rim, therefore, the
> > larger the radius of curvature across a tyre of a given nominal
> > width. The vertical compliance (and therefore the comfort) of
> > the tyre is related to the rate of change of contact patch area
> > with vertical displacement, which increases roughly in proportion
> > to the radius of curvature of tyre cross section at a given pressure.

> Sorry I don't completely understand that.
>
> Let's simplify things by making the object rectangular in cross section
> (or as near to it as we can physically get)......
>
> 100 x 40 x 40 cm inflatable cuboid sausage. Lay it on its long side and
> bounce up and down on top of it. Now do the same with it sat on its end.
> What's the difference?

Peter,

Before I write out a reply, could we just clarify one little point?

Are you taking the ****?

Thanks,

James Thomson

James Thomson wrote:
> "Pete Biggs" <[email protected]>
> wrote:
>
>> James Thomson wrote:

>
>>> The theory is that a tyre will adopt an arc of roughly constant
>>> curvature between the beads. The wider the rim, therefore, the
>>> larger the radius of curvature across a tyre of a given nominal
>>> width. The vertical compliance (and therefore the comfort) of
>>> the tyre is related to the rate of change of contact patch area
>>> with vertical displacement, which increases roughly in proportion
>>> to the radius of curvature of tyre cross section at a given
>>> pressure.

>
>> Sorry I don't completely understand that.
>>
>> Let's simplify things by making the object rectangular in cross
>> section (or as near to it as we can physically get)......
>>
>> 100 x 40 x 40 cm inflatable cuboid sausage. Lay it on its long side
>> and bounce up and down on top of it. Now do the same with it sat on
>> its end. What's the difference?

>
> Peter,
>
> Before I write out a reply, could we just clarify one little point?
>
> Are you taking the ****?

Thanks James. No I'm not taking the **** but bunged some humour in along
the way. Well, it amused me anyway.

Seriously, I find it easier to understand concepts through simplified
exaggerated examples.

First of all, were you explaining how the tyre behaves with its contents,
or is this just about the compliance of the tyre material itself.

~PB

someone wrote:

>> [snippage]
>>> Mavic A719 and A319 deserve places on the short list as well, I think.
>>> I'm very happy with my A719 rear which sometimes takes very heavy loads,
>>> albeit for short distances. Longer distances it's lightly loaded but it's
>>> reassuring to have the strength when it comes to potholes, etc.

Mavics are great. I use them on my touring bike which I use on lengthy
trips on some of the dodgier parts of the National Cycle Network, and
find I can bowl along at speeds approaching on-road, quite heavily
laden, with no damage. The mavic/schwalbe marathon tyre combo is
unbeatable for that sort of cycling, I find.

Simon

"Pete Biggs" <[email protected]> wrote:

> No I'm not taking the **** but bunged some humour in along
> the way. Well, it amused me anyway.

> Seriously, I find it easier to understand concepts through simplified
> exaggerated examples.

There's an old joke that ends, "assume a spherical cow"...

> First of all, were you explaining how the tyre behaves with its contents,
> or is this just about the compliance of the tyre material itself.

I'm describing an inflated tyre.

> > > Let's simplify things by making the object rectangular in
> > > cross section (or as near to it as we can physically get)......

> > > 100 x 40 x 40 cm inflatable cuboid sausage. Lay it on its long
> > > side and bounce up and down on top of it. Now do the same
> > > with it sat on its end. What's the difference?

The problem with your cuboid tyre is that it has one face fully in contact
with the road at any time, and will respond to load by crushing until its
volume has decreased (and its pressure increased) in proportion to the
increased load. That isn't how a pneumatic tyre works.

James Thomson

"Simon Geller" <[email protected]> wrote:

> Mavics are great.

Which Mavics are great?

> I use them on my touring bike which I use on lengthy trips on some
> of the dodgier parts of the National Cycle Network, and find I can
> with no damage. The mavic/schwalbe marathon tyre combo is
> unbeatable for that sort of cycling, I find.

Which competing combinations have you tried, and over what distances?

James Thomson

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