Quoted message said:John Forrest Tomlinson said:Quoted message said:A 175.0 mm pedal drops 2.5 mm lower than a 172.5 mm pedal, about a
tenth of an inch.
The difference in length between your right and left leg is probably
twice that much (or more):
"A majority of people have a measurable leg length difference of 1/4"
or more."
So what? My leg length doesn't change much so I don't see what your
point is.
(My functional leg length did change a little over a long period of
time due to some forms of soft tissue work. That affected my bike
fit.)
Dear John,
In all likelihood, one of your legs is longer than the other by 1/4"
or more, like most people's legs.
That's about twice as much as the difference in distance from your hip
to pedals attached to 175.0 and 172.5 mm cranks.
When walking or running, few of us can tell which of our legs is
shorter.
Our body, in walking around, is not constrained on both ends like the
leg is constrained by the seat and pedals (assuming you use
cliplesspedals or toe clips and straps). Believe me, if someone tied
a noose around your neck just tight enough to not strangle you, and
you somehow shrunk an inch, you'd notice.
That said, I'm certain that if you added a 1/4 inch shim under one of
my legs I'd notice the difference in walking. That is, if you changed
the difference from my normal difference.
I don't know which of my legs is longer (though I used to. The
problem was due to a hip being tilted, and it manifested itself in
knee pain. I think it is the left one). I reduced the difference over
time with help from a chiropractor and other stuff.
Quoted message said:Indeed, most of us don't even know if we're waddling around
on slightly mismatched legs, any more than we notice that we're up to
So what? This is irrelevant since we don't have the option to change
our leg lengths at all.
Quoted message said:an inch shorter by the end of the day, due to the compression of our
spinal disks.
I don't change height anywhere nearly that amount.
Quoted message said:(The change in spinal length during the day says something about how
sensitive we really are to the distance from the seat to the
handlebars.)
Anyone sufficiently curious can ask a friend to swap four 175 and
172.5 crank arms randomly on a bike for a dozen rides, left and right,
and report how well he could tell the difference without looking at
the numbers on the cranks.
You don't know what you are talking about. I've had experiences where
I've gotten on my bike and something felt wrong. And tracked it down
after the ride to the seatpost having slipped a small amount or not
setting the bike up right.
I recently tried to replace the orthotic I use in my cycling shoes and
could not get the thing to feel right -- it felt OK to my feet but my
knees felt tight after 20 minutes, despite the orthotics aligning my
knees and legs just the same as my old ones. Finally I found the
difference -- the new ones are a little thicker under the heel and
ball of the foot. Same manufacturer. Annoying.
Quoted message said:A more entertaining experiment would involve leaving the crank
unchanged and lying to a self-described sensitive rider, telling him
that his 175.0 mm cranks were being changed to 172.5 mm and seeing if
he detected the imaginary changes.
A lot of RBT posters have mentioned that they didn't notice what
turned out to be mismatched cranks.
See my examples above.
--
JT
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