RE: longer cranks? bigger wheel?
Seth Golub wrote:
>What’s the advantage of a larger wheel, assuming correspondingly longer cranks?
>Is it just to make the smaller bumps easier to handle?
>Longer cranks give better leverage, so that should make it easier to go up and
>down steep hills and wrestle over rocks, right? What about the longer range of
>motion my legs will go through? How does that factor in?
An astute observation. With a larger wheel, you need longer cranks to have the
same amount of leverage as the smaller wheel. But then your feet are making
bigger circles. This means a greater range of motion in your legs, a seat that’s
lower in relation to the axle, and more zig-zag in your riding.
What is zig-zag? We should come up with a more official name for this, maybe
“wobble”. It’s the left-right-left-right veering of the wheel as you pedal. Some
people naturally pedal straighter than others, but all of us zig-zag some. You
can see this phenomenon more clearly when slowing down or riding down a steep
hill. If you’ve ever ridden a big wheel unicycle you may have noticed it as
well. As the cranks get longer, your side-to-side leverage on the unicycle
increases as well, and the zig-zag becomes more pronounced. This is an imperfect
description, but should convey the basic concept.
As you zig-zag more, your line becomes longer and your riding less efficient. So
this is another factor to be weighed when choosing crank length/wheel size.
Currently, I use a 24" with 140mm cranks, and a 26" with 150. But I can’t form a
reliable opinion from my equipment. My 24" is a rigid, lightweight Miyata while
my 26" is a cobbled-together, heavy, bendy piece of Schwinn with a tire that
rubs when you pedal hard.
I feel I can go faster on my 24", due to the shorter cranks. Even though the
wheel is bigger on my 26", the long cranks seem to make me work harder on level
ground and downhill. But I’ll be able to form a better opinion soon, when I
start riding my new carbon MUni from Roger Davies. It will have 26" wheel and
152mm cranks, and it will be light & rigid as well.
The only way to decide for yourself is to evaluate the trails on which you ride,
and the type of speed vs. terrain-eating you wish to do.
On Monday of this week I rode the Nassau/Suffolk Greenbelt trail on Long Island.
It’s an awesomely fun trail, full of sharp turns, bumpy roots and log obstacles.
But it doesn’t have many hills. Short cranks work well here.
But at other times I might want to see if I can ride up the Confluence
(expert) trail in Auburn. When it comes to riding uphill, nothing can substitute
for the long cranks.
So what type of riding do you prefer? What kind of trails do you have in your
local area? These are the factors that will help you determine what to ride.
As for me, I’d like a pair of adjustable crank arms. Ones that won’t break,
Stay on top, John Foss