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#1
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Refining choice for a shorter crank. Crank length selection and seat position.
thirty-six wrote:
On Jul 26, 3:38 am, "Steve Freides" wrote: thirty-six wrote: I'm trying to sort out that formula to help others. You've answered this one already by yourself - you know what works for you, so use it. First of all, I don't know what works best or with least effort per mile. It could well be that a 5" or 6" long crank be best. Does the way I've assessed for correct length stand up to scrutiny and so used for others or is there a damning reason to go shorter still? I do understand the claim for an aerodynamic pursuiters position being benefitted by shorter cranks to assist in breathing and reduce aerodynamic drag. That's not a particular requirement for me. A 5" crank would also require a frame change, so the evidence would have to be strong to get me to that size. I suspect that I should be able to use 100mm in saddle length which would indicate that the cranks need to be around 50mm shorter than they are (just because I'm so restricted with them). But this would suggest 120mm cranks. Even a 5" (127mm) crank sounds too small, but I've been conditioned to 165 to 175 as the norm. There is no "perfect" to be had here. As engineers say, everything is a compromise. You have to pick you priorities. As but one example, I'm sure a lot of pro's hate their TT position but, as long as it doesn't get them injured, that's just tough luck for them because performance comes before everything else when you're getting paid for your performance. Don't forget, either, that track bikes (your example of pursuiters) are fixed gears and, as such, crank length has at least a somewhat different meaning. I can tell you from personal experience that when I was recovering from a serious back injury about 15 years ago, I could ride a fixed gear but I couldn't ride a normal bike - mind you, I have no idea if this is significant in the grand scheme of things but I can tell you that things are different when you're on a track, and even when you're on track-style equipment like a fixed gear on the road. If I could sum up my advice to you in a word, it would be "relax" - your quest to improve has to start with being able to perform safely and, especially since, I assume, you're not doing this for a living, anything that causes you back pain after a ride is simply an unacceptable compromise, even if it helped you be faster. OTOH, if you find you prefer to race criteriums with a different size of crank than you use for long road races because it makes you go faster at those shorter distances, well, that would be an example of an OK compromise in my book. Just don't forget that there are tradeoffs in any choice of equipment and it is not - I repeat _not_ - an exact science. -S- |
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#2
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Refining choice for a shorter crank. Crank length selectionand seat position.
I think most fitters seek out a position that is is more dependent on
the riders current flexibility and strength than actual anatomical limitations. Its a compromise of comfort and power, often in a single session, so there's little incentive to prescribe strength and flexibility exercises and evolve a position that is more aero, or uses a longer crank for hills, for example. I do like a local physio who is a former high performance rider and does fittings. She looks more at strength and flexibility of the individual than the knee over pedal type rules of thumb. Still, it's kinda one shot deal, vs a plan to work towards an ideal. |
#3
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Refining choice for a shorter crank. Crank length selectionand seat position.
On Jul 26, 5:10*pm, "Steve Freides" wrote:
thirty-six wrote: On Jul 26, 3:38 am, "Steve Freides" wrote: thirty-six wrote: I'm trying to sort out that formula to help others. You've answered this one already by yourself - you know what works for you, so use it. First of all, I don't know what works best or with least effort per mile. *It could well be that a 5" or 6" long crank be best. *Does the way I've assessed for correct length stand up to scrutiny and so used for others or is there a damning reason to go shorter still? *I do understand the claim for an aerodynamic pursuiters position being benefitted by shorter cranks to assist in breathing and reduce aerodynamic drag. *That's not a particular requirement for me. *A 5" crank would also require a frame change, so the evidence would have to be strong to get me to that size. *I suspect that I should be able to use 100mm in saddle length which would indicate that the cranks need to be around 50mm shorter than they are (just because I'm so restricted with them). *But this would suggest 120mm cranks. *Even a 5" (127mm) crank sounds too small, but I've been conditioned to 165 to 175 as the norm. There is no "perfect" to be had here. *As engineers say, everything is a compromise. *You have to pick you priorities. As but one example, I'm sure a lot of pro's hate their TT position but, as long as it doesn't get them injured, that's just tough luck for them because performance comes before everything else when you're getting paid for your performance. Don't forget, either, that track bikes (your example of pursuiters) are fixed gears and, as such, crank length has at least a somewhat different meaning. *I can tell you from personal experience that when I was recovering from a serious back injury about 15 years ago, I could ride a fixed gear but I couldn't ride a normal bike - mind you, I have no idea if this is significant in the grand scheme of things but I can tell you that things are different when you're on a track, and even when you're on track-style equipment like a fixed gear on the road. If I could sum up my advice to you in a word, it would be "relax" - your quest to improve has to start with being able to perform safely and, especially since, I assume, you're not doing this for a living, anything that causes you back pain after a ride is simply an unacceptable compromise, even if it helped you be faster. *OTOH, if you find you prefer to race criteriums with a different size of crank than you use for long road races because it makes you go faster at those shorter distances, well, that would be an example of an OK compromise in my book. *Just don't forget that there are tradeoffs in any choice of equipment and it is not - I repeat _not_ - an exact science. -S- This is all very interesting but I am not competetively active nor am I likely to be. Yes, I'd prefer to go out for six hours on the bike and get home and not have to worry about having to have a soak, massage and bed rest to help recouperate. If I think objectively it means I should look for the shortest available cranks off the shelf with 9/16" pedal fitting, at a low price... and see what happens. Supposedly I'll need smaller gears. Hmm, my ex-racing bike is slightly undergeared as it is, but I doubt that a135mm BCD crankset exists in the sort of length I am looking for (closer to 120mm than 170mm). I'm too tired now to think much further at the minute but have been considering how the rotation of position as a rider moves into the hooks should move him forward on the saddle. It seems I could have used bars with a greater reach and drop than I did. I favoured the tight bends because my hands were secure over rough tracks, and race circuits are not necessarily on the best roads. |
#4
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Refining choice for a shorter crank. Crank length selectionand seat position.
On Jul 26, 3:26*pm, thirty-six wrote:
On Jul 26, 5:10*pm, "Steve Freides" wrote: thirty-six wrote: On Jul 26, 3:38 am, "Steve Freides" wrote: thirty-six wrote: I'm trying to sort out that formula to help others. You've answered this one already by yourself - you know what works for you, so use it. First of all, I don't know what works best or with least effort per mile. *It could well be that a 5" or 6" long crank be best. *Does the way I've assessed for correct length stand up to scrutiny and so used for others or is there a damning reason to go shorter still? *I do understand the claim for an aerodynamic pursuiters position being benefitted by shorter cranks to assist in breathing and reduce aerodynamic drag. *That's not a particular requirement for me. *A 5" crank would also require a frame change, so the evidence would have to be strong to get me to that size. *I suspect that I should be able to use 100mm in saddle length which would indicate that the cranks need to be around 50mm shorter than they are (just because I'm so restricted with them). *But this would suggest 120mm cranks. *Even a 5" (127mm) crank sounds too small, but I've been conditioned to 165 to 175 as the norm. There is no "perfect" to be had here. *As engineers say, everything is a compromise. *You have to pick you priorities. As but one example, I'm sure a lot of pro's hate their TT position but, as long as it doesn't get them injured, that's just tough luck for them because performance comes before everything else when you're getting paid for your performance. Don't forget, either, that track bikes (your example of pursuiters) are fixed gears and, as such, crank length has at least a somewhat different meaning. *I can tell you from personal experience that when I was recovering from a serious back injury about 15 years ago, I could ride a fixed gear but I couldn't ride a normal bike - mind you, I have no idea if this is significant in the grand scheme of things but I can tell you that things are different when you're on a track, and even when you're on track-style equipment like a fixed gear on the road. If I could sum up my advice to you in a word, it would be "relax" - your quest to improve has to start with being able to perform safely and, especially since, I assume, you're not doing this for a living, anything that causes you back pain after a ride is simply an unacceptable compromise, even if it helped you be faster. *OTOH, if you find you prefer to race criteriums with a different size of crank than you use for long road races because it makes you go faster at those shorter distances, well, that would be an example of an OK compromise in my book. *Just don't forget that there are tradeoffs in any choice of equipment and it is not - I repeat _not_ - an exact science. -S- This is all very interesting but I am not competetively active nor am I likely to be. *Yes, I'd prefer to go out for six hours on the bike and get home and not have to worry about having to have a soak, massage and bed rest to help recouperate. *If I think objectively it means I should look for the shortest available cranks off the shelf with 9/16" pedal fitting, at a low price... *and see what happens. Supposedly I'll need smaller gears. *Hmm, my ex-racing bike is slightly undergeared as it is, but I doubt that a135mm BCD crankset exists in the sort of length I am looking for (closer to 120mm than 170mm). I'm too tired now to think much further at the minute but have been considering how the rotation of position as a rider moves into the hooks should move him forward on the saddle. * It seems I could have used bars with a greater reach and drop than I did. I favoured the tight bends because my hands were secure over rough tracks, and race circuits are not necessarily on the best roads. Go for the comfort and ergonomics ("protection from injury/ discomfort"). Try the 165's on a bike that otherwise suits you and see what happens. Worked for me. --D-y |
#5
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Refining choice for a shorter crank. Crank length selection and seat position.
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#6
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Refining choice for a shorter crank. Crank length selection and seat position.
mtb Dad wrote:
I think most fitters seek out a position that is is more dependent on the riders current flexibility and strength than actual anatomical limitations. Its a compromise of comfort and power, often in a single session, so there's little incentive to prescribe strength and flexibility exercises and evolve a position that is more aero, or uses a longer crank for hills, for example. I do like a local physio who is a former high performance rider and does fittings. She looks more at strength and flexibility of the individual than the knee over pedal type rules of thumb. Still, it's kinda one shot deal, vs a plan to work towards an ideal. Yes, I agree - the better the fitter can look at the person getting fitted in all their aspects, the better the results will be, e.g., if someone comes in who's obviously athletic, looks like they're open to advice, and has tight hamstrings, then the best thing might be to suggest working on the hamstrings for a while before having a fit kit done. I'm showing my exercise prejudice here, but the kettlebell swing and barbell deadlift both have potential to solve tight hamstrings and improve strength as well. I used to always have to lower my saddle every Spring because I'd lost some of my cycle-specific flexibility over the winter, but once I started doing kettlebell swings regularly, that problem went away and has never come back. Disclaimer: I'm an instructor (actually, an instructor's instructor) in the RKC program, see here http://www.dragondoor.com/steve-freides/?apid=1022 The picture should let you know I don't have hamstring flexibility problems. -S- |
#7
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Refining choice for a shorter crank. Crank length selectionand seat position.
On 7/26/2011 3:26 PM, thirty-six wrote:
[...] Supposedly I'll need smaller gears. Hmm, my ex-racing bike is slightly undergeared as it is, but I doubt that a135mm BCD crankset exists in the sort of length I am looking for (closer to 120mm than 170mm).[...] If you want cranks that short, here is the place: http://bikesmithdesign.com/Short_Cranks/index.html. Sheldon Brown's Gain Ratio calculator can assist in helping you decide what size chainwheels you want with different crank lengths: http://sheldonbrown.com/gears/. -- Tºm Shermªn - 42.435731°N, 83.985007°W I am a vehicular cyclist. |
#8
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Refining choice for a shorter crank. Crank length selectionand seat position.
On Jul 27, 9:41*pm, "Steve Freides" wrote:
wrote: Go for the comfort and ergonomics ("protection from injury/ discomfort"). Try the 165's on a bike that otherwise suits you and see what happens. Worked for me. --D-y +1 - based on everything you've said, it sounds like you'll be happy with 165's. I wouldn't change your gearing at all - you can always do that later if you need, but the difference isn't that dramatic that you have to run out and buy a new drivetrain. -S- On my second bike (same size, softer stays) I have 165s, I'm thinking that with smaller crank again I will resort to a wind-cheating position more frequently without fear of incurring hamstring strain leading to back pain. From what I can make out there is little I can lose out on. It's a little further to get up and down from but the payoff is greater lean angles (at least in the dry) and more capable off-road use. I fully understand the requirement to do hamstring stretches for a racing position with the typical length cranks, but I usually want to just jump on the bike and go, exactly like when I was 16. |
#9
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Refining choice for a shorter crank. Crank length selection and seat position.
thirty-six wrote:
On Jul 27, 9:41 pm, "Steve Freides" wrote: wrote: Go for the comfort and ergonomics ("protection from injury/ discomfort"). Try the 165's on a bike that otherwise suits you and see what happens. Worked for me. --D-y +1 - based on everything you've said, it sounds like you'll be happy with 165's. I wouldn't change your gearing at all - you can always do that later if you need, but the difference isn't that dramatic that you have to run out and buy a new drivetrain. -S- On my second bike (same size, softer stays) I have 165s, I'm thinking that with smaller crank again I will resort to a wind-cheating position more frequently without fear of incurring hamstring strain leading to back pain. From what I can make out there is little I can lose out on. It's a little further to get up and down from but the payoff is greater lean angles (at least in the dry) and more capable off-road use. I fully understand the requirement to do hamstring stretches for a racing position with the typical length cranks, but I usually want to just jump on the bike and go, exactly like when I was 16. "... exactly like when I was 16." Well, that's a conversation starter, for sure. There are a lot of things that you just can't do exactly like when you were 16. According to my wife, some of those changes are for the better. But you must realize that as you get older, retaining the _functionality_ you had when you were younger requires _work_. If you aren't willing to do the work, you will have to accept the reduced functionality. No one is telling you to do a half-hour yoga routine every time before you ride, but if 30 seconds of toe touches help, then that seems to me to be a more than worthwhile tradeoff. And here's another good thing to think about - if you do the stretching _most_ of the time, you can get away with missing it once in a while. Our bodies remember what we're able to do and not do very well, and you'll still have the hamstring flexibility, or at least most of it, on those times you skip the stretches. Me, I'd be happy to ride fast enough that cheating the wind made a lot of difference. -S- |
#10
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Refining choice for a shorter crank. Crank length selectionand seat position.
On Jul 29, 6:52*am, thirty-six wrote:
On Jul 27, 9:41*pm, "Steve Freides" wrote: wrote: Go for the comfort and ergonomics ("protection from injury/ discomfort"). Try the 165's on a bike that otherwise suits you and see what happens. Worked for me. --D-y +1 - based on everything you've said, it sounds like you'll be happy with 165's. I wouldn't change your gearing at all - you can always do that later if you need, but the difference isn't that dramatic that you have to run out and buy a new drivetrain. -S- On my second bike (same size, softer stays) I have 165s, I'm thinking that with *smaller crank again I will resort to a wind-cheating position more frequently without fear of incurring hamstring strain leading to back pain. *From what I can make out there is little I can lose out on. *It's a little further to get up and down from but the payoff is greater lean angles (at least in the dry) and more capable off-road use. * I fully understand the requirement to do hamstring stretches for a racing position with the typical length cranks, but I usually want to just jump on the bike and go, exactly like when I was 16. Don't know if this has been talked about, but this is the great discovery of triathletes. By having 78 degree angles on their bikes, they can get really low and the angle between their lower backs and the hamstring is not as steep. I used to get back pain after riding about 40 miles and would have to get off my bike and stretch. I had a custom built ti frame made in china for peanuts with a 76 degree angle. Now, I can ride aero non- stop for miles on end without getting a tight lower back. I usually ride around 50 miles, non-stop every sat and sunday. No back problems to report. It was a huge difference for my short femurs to get a 170 crankset and a 76 degree angle. I do have a 73.5 angle bike. But, but, but....I have the longest saddle possible, fairly forward, and I tend to sit up front. Also, no problems with my lower back. I noticed that most of my buddies ride on the brake hoods. I ride on the drops all the time. I believe that most people would be much more comfortable on 76 to 78 degree angled bikes. But, since 23 year old, ultra fit, pros, who ride a million miles a day ride 73 degree angles, all bikes are designed like that. When you buy a bike from a local bike shop, they fit you as if you were Lance Armstrong. |
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