I've actually gone the other way, from 175s to 170s. I did it for knee pain. The 5mm difference is
none on the knee extension, since saddle height is measured from an extended crank. But there is 5
times 2, or 10 mm of difference in flexion, since the saddle with a 175 is lower, and yet the other
crank comes up 5 mm higher.
Going from a 170 to a 175 gives a longer lever, which means more torque, which has a similar effect
of adding two teeth to each cog in the rear.
"Bill Davidson" <[email protected]
> wrote in message news:[email protected]
> Wayne T wrote:
> > I am 6'4" with a 34" inseam. I ride a 25 1/2" touring road bike. My
> > size is a 170. Been riding with it for 30 years. Builder thinks I
> > go to a 175 since I am getting a new crank. What exactly would this do
> > me.
> Proably not a lot. There are those that disagree:
> Judge for yourself. Personally, if I used that guy's formula, I'd be
> a 197mm crank (36" inseam), which is somewhat difficult to come by. I might need a new frame for
> that in order to maintain ground clearance (it would put my pedals almost an inch closer to the
> ground which could be a problem when pedaling through turns). Right now, I'm sticking with my
> > Would it improve pedal efficiency?
> It will give you very slightly better leverage actually (slightly longer lever). It will reduce
> your gain ratio a bit (effectively lowering your gears slightly) and allow you produce slightly
> more torque with the same amount of effort, which may help you up the hills a little. It's
> probably not enough to be all that significant though.
> > Also, would it be harder on the knees?
> Probably not. They will have a slightly larger amount of movement to account for the bigger
> pedaling circle but we're not talking about a lot here and since you're getting better leverage,
> it will likely be slightly easier on your knees. By the time you get to the power part of your
> stroke, you knee will actually be slightly straighter than with a shorter crank, which should be a
> good thing.
> --Bill Davidson
> Please remove ".nospam" from my address for email replies.
-----------== Posted via Newsfeed.Com - Uncensored Usenet News ==----------
The #1 Newsgroup Service in the World!
-----= Over 100,000 Newsgroups - Unlimited Fast Downloads - 19 Servers =-----