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Crank arm length question
The root question:
How do I determine the appropriate starting-point for crank-arm length? The background: I have posted in the past about a minor soreness across the top of my kneecap which shows up several miles into a ride, and which always goes away by the next day. I have raised my seat as much as I can without rocking my hips, and the last adjustment of 3mm or so a month ago helped significantly, but not completely. Some other reading I've done has indicated that a too-long crank arm can contribute to knee soreness, which of course brings up the question of how to determine the correct length. My current ones are 175mm, and I wear pants with a 32 inch inseam (I haven't measured my crotch-to-ground height yet). Is it likely that a shorter crank might help? If so, how short? -- Remove the ns_ from if replying by e-mail (but keep posts in the newsgroups if possible). |
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Crank arm length question
On Mon, 17 May 2004 10:06:31 -0400, David Kerber
wrote: The root question: How do I determine the appropriate starting-point for crank-arm length? Find a helpful bike shop that will let you try different lengths? The background: I have posted in the past about a minor soreness across the top of my kneecap which shows up several miles into a ride, and which always goes away by the next day. I have raised my seat as much as I can without rocking my hips, and the last adjustment of 3mm or so a month ago helped significantly, but not completely. Some other reading I've done has indicated that a too-long crank arm can contribute to knee soreness, which of course brings up the question of how to determine the correct length. My current ones are 175mm, and I wear pants with a 32 inch inseam (I haven't measured my crotch-to-ground height yet). Is it likely that a shorter crank might help? If so, how short? Have you tried moving the seat forward? That took away my upper kneecap aches. I've even lowered the saddle down a bit, having raised it again and again while the seat was back, and things are fine. A discussion of crank length, with links to other articles- http://www.myra-simon.com/bike/cranks.html |
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Crank arm length question
David Kerber wrote:
The root question: How do I determine the appropriate starting-point for crank-arm length? snip Seems to be a rather hearty investigation of the subject he http://www.cranklength.info/index.htm - khill |
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Crank arm length question
On Mon, 17 May 2004 13:50:13 -0400, David Kerber
wrote: The seat's already close to as far forward as it can go, but I'll see if I've got any room left at all. Some (most?) seatposts have the clamp slightly offset instead of centered over the tube; turn the seatpost around, remount the saddle, and make sure there's still enough tilt available (not always). -- Rick Onanian |
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Crank arm length question
On Mon, 17 May 2004 10:06:31 -0400, David Kerber
wrote: My current ones are 175mm, and I wear pants with a 32 inch inseam (I haven't measured my crotch-to-ground height yet). Is it likely that a shorter crank might help? If so, how short? 175 is pretty long. I used 172.5 with my 30 inch inseam, but went down to 165 and am surprisingly happy; I expected not to like them. -- Rick Onanian |
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Crank arm length question
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Crank arm length question
On Mon, 17 May 2004 10:06:31 -0400, David Kerber
wrote: My current ones are 175mm, and I wear pants with a 32 inch inseam (I haven't measured my crotch-to-ground height yet). Is it likely that a shorter crank might help? If so, how short? 175 is pretty long. I used 172.5 with my 30 inch inseam, but went down to 165 and am surprisingly happy; I expected not to like them. I'm not so sure about that. My Levi's are a 32 inch inseam and I run 175's on my mountain bike and tandem, and 172.5's on my road bike. My wife has a 28 inch inseam and rides 165's. YMMV. Chris Neary "Science, freedom, beauty, adventu what more could you ask of life? Bicycling combined all the elements I loved" - Adapted from a quotation by Charles Lindbergh |
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Crank arm length question
I wrote:
175 is pretty long. I used 172.5 with my 30 inch inseam, but went down to 165 and am surprisingly happy; I expected not to like them. On Wed, 19 May 2004 01:23:52 GMT, Chris Neary wrote: I'm not so sure about that. My Levi's are a 32 inch inseam and I run 175's on my mountain bike and tandem, and 172.5's on my road bike. Mountain bikes have very different requirements for crank length. I don't know anything about tandems. My wife has a 28 inch inseam and rides 165's. Make sure you're measuring both your inseams accurately; for biking purposes, it's not which pants are comfortable, but rather the exact height from the floor to your crotch. One method I read somewhere is to stand with your feet flat and your back (and legs) against a wall, and hold a book with one edge against the wall and one edge up to your leg joint (as high as it can), and measure from the book's crotch edge to the floor. Of course, having said that, I don't remember if my inseam was 30 inches when I measured that way. YMMV. Agreed...In fact, that's the most important rule about crank length. -- Rick Onanian |
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Crank arm length question
My Levi's are a 32 inch inseam and I run 175's on my mountain bike and
tandem, and 172.5's on my road bike. Mountain bikes have very different requirements for crank length. I don't know anything about tandems. Mountain bikes, tandems, and time trial bikes tend to have slightly longer cranks since cadence on these bikes is usually lower but torque is somewhat higher. Fixed gear bikes, OTOH, tend to run shorter cranks for the opposite reason, as well to avoid pedal strikes in some instances. My fixie has 170mm cranks. My wife has a 28 inch inseam and rides 165's. Make sure you're measuring both your inseams accurately; for biking purposes, it's not which pants are comfortable, but rather the exact height from the floor to your crotch. One method I read somewhere is to stand with your feet flat and your back (and legs) against a wall, and hold a book with one edge against the wall and one edge up to your leg joint (as high as it can), and measure from the book's crotch edge to the floor. Of course, having said that, I don't remember if my inseam was 30 inches when I measured that way. I answered the question as I did since the original poster only supplied his pants inseam. What size pants do you wear? Chris Neary "Science, freedom, beauty, adventu what more could you ask of life? Bicycling combined all the elements I loved" - Adapted from a quotation by Charles Lindbergh |
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