Re: Wheel-less tire question

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