DougC wrote:
> Johnny Sunset aka Tom Sherman wrote:
> > Tracer wrote:
> > ....
> > My only real caution would be is that the STX comes in only one size,
> > and will either not fit or have to much weight on the real wheel if the
> > rider is much over 6 feet (0.183 m) tall [2].
> > ....
> > [2] Assuming normal range body proportions.
> >
> Yes but is a lightly-loaded front wheel on a recumbent so bad of a
> thing?
On a RANS Tailwind, I can amuse myself by doing power wheelies from a
dead stop.
Too little weight on the front wheel can make handling during low speed
riding, especially climbing difficult, particularly if the front wheel
comes off the ground, as it did with every pedal stroke on my RANS
Rocket when climbing the steeper part of this road. [1] [2] The late
Gardner Martin reportedly did not put a larger than ISO 451-mm wheel on
the front of Easy Racers, since obtaining proper weight distribution
would have made an already long bicycle even longer.
> During emergency braking much of the total weight shifts to the
> front wheel, and people frequently note that they crash because their
> front wheel begins to slide. Tires slide because either they are
> overloaded for what traction they have, or because they are overinflated
> for conditions.
As long the the coefficient of friction remains relatively linear, the
increased loading will produce a similar increase in traction.
> It seems logical to have weight distribution proportional to where the
> CG of the bicycle lies but in real-world terms it may be useful to have
> an "underweighted, underloaded, underinflated" front wheel in
> anticipation of making emergency stops.
Assuming adequate braking power, one of two things will happen at the
limit: the bike will rotate about the contact patch of the front tire
or the front tire will slide. As long as the CG is some combination of
far enough rearward and low enough that the front tire will slide under
braking, no further improvement in braking will occur by moving the CG
further rearward.
> Cruising down the road with most of your weight on the rear tire doesn't
> hurt anything,
It will increase rolling resistance due to the greater deformation of
the rear tire casing and resultant energy loss through hysteresis. The
tire deflection could be reduced by increased tire pressure, but this
is limited by tire blow-off and rim strength factors of safety, and
ride comfort on non-suspended bicycles.
> but crashing when your front tire slides out under hard
> braking does. And certainly any bicycle can brake hard just fine on
> /clean pavement/,,,, it's when you need to brake hard while turning on
> a patch of gravel or sandy pavement that is the test.
Generally, experience shows that LWB bicycles with lightly loaded front
wheels are worse on loose surfaces than SWB bicycles with more heavily
loaded front wheels.
[1]
<http://terraserver.microsoft.com/image.aspx?T=2&S=12&Z=16&X=581&Y=5541&W=2&qs=%7cperrysville%7cin%7c>.
[2] The front wheel would likely have stayed on the ground if I had had
a lower gear than the stock 39/28 or a 2001 or later RANS Rocket which
has longer chain stays.
--
Tom Sherman - Behind the Cheddar Curtain
Post Free or Die!