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From: (Jobst Brandt)
Subject: Re: First Wheel Building Results
Date: 4 Dec 2000 17:20:50 GMT

Peter Remner (aka Izzy for some reason) writes:

>>>>> Are you saying that wheels DON'T affect the quality of the ride?

>>>> That is correct.  Do you have any idea what the elastic deflections
>>>> of a bicycle rim are?  If you measured this you wouldn't make such
>>>> claims.  Tires and inflation are the only effect that you can feel
>>>> among wheels that are durable enough to be ridden for any distance
>>>> like 100 miles.  A couple of years ago wavy spokes were offered for
>>>> "a better ride".  You couldn't feel the difference but the spokes
>>>> broke in about that distance anyway.

>>> I think what we need to focus on isn't pure elastic deflection, but
>>> factors like weight, sound, and vibration.

>> I've focused on that and done the analysis.  They do not enter into
>> "ride quality", the transmission of road shock.

> The transmission of road shock is not all there is to ride quality.
> Transmission of road shock is an objective measurement, while
> "ride quality" is a *subjective* measurement.

How do you propose to measure and quantify this?  It reminds me of the
local car wash slogan "A clean car drives better!" and right they are
for many people.  I recall as a child, cleaning my bicycle and
imagining how much better it rode.  Some folks never leave that realm.
They drive cars with all sorts of gimmicks, fins, extra lights,
expensive polished wheels and many more, believing the car works
better that way and now you are going to measure that, or at least
convince others of your perception.

>>> I remember temporarily swapping a steel-rimmed wheel (sorry) onto
>>> my roadie.  It "felt" much harsher.  Tires were the same, same
>>> pressure, even the same rim strip.

>> There's something wrong with this picture and it may begin with "I
>> remember" because steel rims do not have hooked beads and do not allow
>> inflation pressures much over 60 psi.  At such pressures, for road
>> tires, there isn't much to be felt but tire mush.  Let's not overlook
>> that radial deflection of a wheel is on the order of 0.001" to 0.003"
>> over average pavement and that the difference between two wheels is a
>> small fraction of that.

> Steel rims don't have hooked beads?  Wow.  You're really losing credibility.

> These weren't Schwinn SA-3 rims, they were cheapy got-em-from-the-trash
> 27" wheels, with steel rims, and they most certainly did have hooked beads.

OK, so you found a hooked bead steel rim.  I suppose you noticed that
is was distinctly heavier than the aluminum hollow cross section rim
to which you are comparing it.  Why don't you just say you thought the
lighter wheel steered differently, not even better because riding
no-hands is easier with a heavier wheel.  If you want to put that into
"ride quality" than you ought to define that first.

> Here's something to chew on: Automobiles have suspensions with
> plenty of travel and tires that are big low-pressure doughnuts, yet
> there is a large field of research in rubber bushings, and not just
> the ones at the pivot points but isolating the subframes that the
> suspension attaches to to the rest of the chassis.  They do not
> appreciably deflect, yet they are important for "ride quality".  Or
> would you say that is bunk, too?  After all there is MUCH more
> movement in the suspensions and the tires, therefore any deflection
> anywhere else is not significant?

A car is a large resonating drum enclosure, whose smooth and silent
characteristics are one of the challenges for automotive engineers.
The two main methods of attacking this problem are sound damping in
the car and isolation from the road.  Road shock has three levels of
isolation.  Wheel suspension absorbs large displacements, tires, small
rapid displacements and rubber isolation for high frequencies that are
not attenuated especially by radial tires that have practically no
losses to dampen frequencies on the order of asphalt pavement
granularity.  It was the radial tire that brought on the isolated
sub-chassis for wheel suspension.

>>> The only way I can figure, is that the rim was heavier and was
>>> affected by bumps more, and there was a metal spoke protector that I
>>> was too lazy to remove (sleazeball that I am) that rattled just a
>>> bit over bumps.  The back end also seemed a bit louder when hitting
>>> small bumps when the protector wasn't rattling.  The brain will
>>> percieve thumps and rattles as "rough ride", it's been proven in NVH
>>> studies in the automotive field.  People will say a smooth riding
>>> but noisy car "rides worse" than a quiet yet stiff one.

>> You're dodging and weaving.  Lets just leave it at that.

> Who's dodging and who's weaving?

First it was ride quality, a vague attribute, and then it slipped into
acoustic response.  That is dodging and weaving to me.  Besides, spoke
size and rim material does not affect acoustic response even slightly
compared to tire selection ansd inflation pressure.

Jobst Brandt      <>

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