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From: Roger Merriman <roger@sarlet.com>
Newsgroups: rec.bicycles.tech
Subject: Re: Wheel-less tire question
Date: 13 Mar 2025 19:08:49 GMT
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Mark J cleary <mcleary08@comcast.net> wrote:
> On 3/13/2025 1:36 PM, Roger Merriman wrote:
>> AMuzi <am@yellowjersey.org> wrote:
>>> On 3/13/2025 11:29 AM, bp@www.zefox.net wrote:
>>>> This is mostly a philosophical question, but maybe it has a technical answer.
>>>> 
>>>> The rim of a bike wheel is a relatively heavy component, largely because
>>>> of its circumference. Could it be dispensed with, at least in the case of
>>>> a tubular tire, by making the spokes extensions of the tire carcass cords?
>>>> The hub would remain mostly the same, with the "spoke" cords of the tire
>>>> laced around anchors on the hub flanges.
>>>> 
>>>> It wouldn't be very convenient to handle, indeed, a spider's nightmare.
>>>> But, it could fold up much like a parachute. The tire would have to be
>>>> inflated to a pressure sufficient to support the needed spoke tension,
>>>> which might be rather higher than the pressure used in traditional
>>>> tubular tires.
>>>> 
>>>> It would be hard to manufacture, getting all the spoke lengths matched
>>>> to run true being the most obvious difficulty. But intuition suggests
>>>> it would be about the lightest construction possible, as well as the
>>>> most compact when stowed before use.
>>>> 
>>>> Another way of asking the same question is to ask the stiffness of a
>>>> fully-inflated, unmounted tubular tire compared to a traditional wood
>>>> or metal wheel rim.
>>>> 
>>>> I've never handled one and so have difficulty guessing.
>>>> 
>>>> Thanks for reading, and any insights.
>>>> 
>>>> bob prohaska
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>> 
>>> Short answer = no.
>>> 
>>> A tensioned wheel, (as bicycles wheels with actual tensioned
>>> spokes, not including carbon sheets) has to have a
>>> noncompressible* rim of constant* circumference in order to
>>> not flop around.  It's an elegant thing, with among the
>>> highest strength to weight ratios of human built structures.
>>> 
>>> The principles are similar to an arch:
>>> 
>>> https://tse2.mm.bing.net/th?id=OIP.OtdqiBPMvo3_wmobAocS0AHaEN&pid=15.1&w=474&h=274&c=7
>>> 
>>> Tension inward on the spoke is compressing the rim
>>> circumference making a rigid structure. Vertical load on an
>>> arch (keystone) is supported by the sides, with load along a
>>> vector (not vertical as a post and lintel). An arch made of
>>> cooked gnocchi would of course fall apart, as would a
>>> bicycle wheel with a fabric 'rim'.
>>> 
>>> Pressed steel auto wheels are different, in that there is
>>> not a tension component. The face behaves like an infinite
>>> series of compression spokes (as wooden wheels use) and as
>>> such is heavier for any given strength.
>>> 
>>> Further to all that:
>>> https://www.astounding.org.uk/ian/wheel/
>>> 
>>> *practically but not absolutely
>>> 
>>> 
>> 
>> Indeed good reasons why spokes haven’t been replaced, much like the chain
>> it’s just too good!
>> 
>> Roger Merriman
>> 
> Seems many hate spokes and weight what can we do to get rid of them and 
> my friend, spokes are your friend. I don't use 36 spoke rims I admit but 
> would if I had to and the conditions warranted it. You can ride 36 hole 
> rim with a bad spoke but try with 20 spoke rim?
> 

All of my bikes are 32 with the exception of the Gravel bike that has
aftermarket wheels with 28 quite frankly they are almost certainly the
strongest wheels in my fleet, the commute bikes both roadie and MTB derived
the wheels are quite budget!

The full sus still has it’s original wheels, but I think MTB’s while hard
on tyres are less hard on wheels, I am toying with a new wheelset as I
suspect I’d notice the difference, not as dramatic as on the Gravel bike as
that included going hydraulic disks and tubeless.

But definitely a thought.

Roger Merriman