Jerrick said:http://www.recumbents.com/WISIL/qfactor/qfactor.htm
I would not approach that definition as, uh, definitive. For Sheldon
Brown fans, which includes me, start by having a look at his two
different meanings of Q-factor:
http://www.sheldonbrown.com/gloss_q.html#qfactor
For what we're talking about, he uses the term "tread":
http://www.sheldonbrown.com/gloss_tp-z.html#tread
Sheldon's description of tread seems like a great explanation of what
we're talking about when we reference Q-factor. Plus the word "tread"
is much more descriptive. We should probably start using that when we
talk about the overall width of unicycle "drive trains." Then we can
use either "offset" or "Q-factor" when talking about the outward
angling of cranks. To me, offset makes a lot more sense, if only in
terms of no longer having to explain it every few weeks on this web
site. 🙂
So, to sum up what Sheldon Brown's site says:
Tread is the lateral distance between the pedal holes on the unicycle.
This is represented as the closest together your feet can be while
riding. In this definition, crank offset is part of the overall
measurement. Think of "tread" as your "stance" if your wheel
disappeared and you were suddenly standing on the ground with your feet
still on the pedals.
As your tread gets wider, your pedaling force is being applied further
and further from your center of mass. The reactive force of your
pedaling will push your body a little bit in the opposite direction.
This is *part of* where wheel wobble comes from on unicycles.
All other things being equal, a wider tread makes for more wobble in
your riding.
A wider tread also puts your pedals closer to the ground when turning.
There is also the medical side of all this. Some people don't mind
pedaling at a wider stance, while others may have orthopedic problems.
Just like seats, what works for you may not be the best for someone
else and vice-versa.
In general, a narrow tread is good for speed. When you're pumping fast,
anything to make the process more efficient will have noticeable
benefits. Less tread lowers the mechanical effort you're putting out.
But narrow has its limits. Narrow wheels are weaker than wide ones, so
as with all things, you must strike a balance that works for the type
of riding you're doing. A road racing unicycle can have a very narrow
wheel, while a MUni or Trials unicycle needs a lot more wheel strength
to be viable.
A wide tread is good for power and control. George Peck, the
"grandfather" of rough terrain unicycling, prefers the very wide tread
of his ultimate wheels made from MTB wheels with cranks, over the more
traditional wooden kind that have almost no tread at all. He says it
gives him more control. Also this wide tread is much less noticeable at
low speeds.
So, whaddaya say we stop with the confusing "Q-factor" and start
calling it "Tread" like Sheldon Brown does?
--
johnfoss
John Foss
Email: "jfoss" at "unicycling.com" -- www.unicycling.com
-----------------------------------------------
"pretty much every trail that we've done on the California or Moab Muni
weekends is an XC trail." -- Kris Holm, on XC from a North Shore point
of view
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