Speedi Posted September 1, 2008 Share Hi everyone... Just want to know a couple of things about a FC 7800 DA crank: Can you replace the DA blades with 105/ultegra blades? And also, Im about 1.78 tall. Is a 172.5mm to small for me? Im currently using a 175mm, was told thats too big for me. And how about maintenance on the Dura Ace cranks? Link to comment Share on other sites More sharing options...
XTC OKE Posted September 1, 2008 Share you really want that crank! Link to comment Share on other sites More sharing options...
Johan Bornman Posted September 1, 2008 Share I don't know about the blade compatibility. The Shimano gurus will tell you that. However, the crank is fine. The difference is very small and very few people can tell whether they're riding a 172.5 or 175mm crank without looking. I have a 165 on my stationery bike and I'm none the poorer or wiser. Crank lengh relates to femur length, not body length. But forget all this, if a specific crank pops up that you want, get it. The length is irrelevant to you and I. Cranks require no maintenance. Link to comment Share on other sites More sharing options...
Speedi Posted September 1, 2008 Share I don't know about the blade compatibility. The Shimano gurus will tell you that. However' date=' the crank is fine. ? The difference is very small and very few people can tell whether they're riding a 172.5 or 175mm crank without looking. I have a 165 on my stationery bike and I'm none the poorer or wiser. ? Crank lengh relates to femur length, not body length. But forget all this, if a specific crank pops up that you want, get it. The length is irrelevant to you and I. ? Cranks require no maintenance. ? ?[/quote'] Ok, well if crank length is so unimportant, then why is it linked to knee problems etc. I think it makes quite a difference... Spoke to a well known cyclist earlier, and he said it would make a difference and you can feel it. Before calling it "irrelevant to you and I", do some research.Speedi2008-09-01 12:42:24 Link to comment Share on other sites More sharing options...
dylankeyter Posted September 1, 2008 Share I don't know about the blade compatibility. The Shimano gurus will tell you that. However' date=' the crank is fine. The difference is very small and very few people can tell whether they're riding a 172.5 or 175mm crank without looking. I have a 165 on my stationery bike and I'm none the poorer or wiser. Crank lengh relates to femur length, not body length. But forget all this, if a specific crank pops up that you want, get it. The length is irrelevant to you and I. Cranks require no maintenance. [/quote'] Ok, well if crank length is so unimportant, then why is it linked to knee problems etc. I think it makes quite a difference... Spoke to a well known cyclist earlier, and he said it would make a difference and you can feel it. Before calling it "irrelevant to you and I", do some research. I think he is suggesting you are not professional and do not spend 6 hours on the bike a day, so he has a point. Link to comment Share on other sites More sharing options...
singletrackmind Posted September 1, 2008 Share I have a 105 blade on my DA crank speedi, works fine Link to comment Share on other sites More sharing options...
turtlek Posted September 1, 2008 Share ok guys the difference in the crank length relates to how far your pedals travel in one rotation and you can definitely feel the difference between a 172.5 and a 175 if you ride a crank that is too long for you it will effectively tigthen up your ITB and render it useless because eventually it will snap (the ITB) and people relate this to knee problems because the ITB is attached to your knee giving you discomfort so it is bad to have cranks that are too long but not neccissarily if you go too short Oh yes i ride a Dura Ace chainring on my ultegra crank!!!turtlek2008-09-01 12:58:37 Link to comment Share on other sites More sharing options...
carlo_sg Posted September 1, 2008 Share Oh yes i ride a Dura Ace chainring on my ultegra crank!!! post a pic please, wanna see how it looks... Link to comment Share on other sites More sharing options...
turtlek Posted September 1, 2008 Share Carlo Pm me with your cell phone number i will MMS it to you now i haent downloaded my pics onto the PC yet Link to comment Share on other sites More sharing options...
controlc Posted September 1, 2008 Share Ok' date=' well if crank length is so unimportant, then why is it linked to knee problems etc. I think it makes quite a difference... Spoke to a well known cyclist earlier, and he said it would make a difference and you can feel it. Before calling it "irrelevant to you and I", do some research.[/quote'] I don't need the advice of a dodgy design website - I can do my own research at home. I go with JB on this one. My bike has a 175mm, not because I chose it, but because that's what came with the bike. My one IDT has a 172.5mm crank and the other one has a 165mm.I can go for a 4hr long cycle on the 175mm bicycle, and then hop onto the 165mm IDT and NOT notice the difference. Face it, the difference between a 175 & 172.5 is VERY small. The sole on my shoes wear out more than that. Link to comment Share on other sites More sharing options...
GoLefty!! Posted September 1, 2008 Share I ride 172.5mm on the roadie and 175mm on the mtb.I can't feel the difference. Tight ITB is due to a lack of stretching but i'm sure the poster was just being sarcy Link to comment Share on other sites More sharing options...
GIRR Posted September 1, 2008 Share Has anyone with a powermeter compared different length crank arms? Pleeeease... so this "feel" thing can be put to rest. Link to comment Share on other sites More sharing options...
turtlek Posted September 1, 2008 Share I ride 172.5mm on the roadie and 175mm on the mtb. I can't feel the difference. Tight ITB is due to a lack of stretching but i'm sure the poster was just being sarcy Good eyes dude!!!!! Link to comment Share on other sites More sharing options...
Johan Bornman Posted September 1, 2008 Share Ok' date=' well if crank length is so unimportant, then why is it linked to knee problems etc. I think it makes quite a difference... Spoke to a well known cyclist earlier, and he said it would make a difference and you can feel it. Before calling it "irrelevant to you and I", do some research.[/quote'] Knee problems are mostly attributed to to saddle height and pedal float issues. Crank length can be related to stride length or step height. The human anatomy is quite tolerant to relatively small differences. We can run up and down stairs of varying height and adapt stride to fall in pace with others (soldiers marching) with no ill effect. Short people don't require different stairs than tall people. Even very tall people will only run up stairs two at a time, not three at a time. Observe and you'll believe. The same goes for cranks. The difference between a circle with a radius of 172,5mm and 175mm is 1,4%. The difference between a 6-footer and a 5'-6 incher is far more than that with no ill effect when using the same crank. I have seen no study that links knee problems to small differences in crank lengths, nor have I seen studies to link optimised power output to optimised crank lengths (within 2.5mm). However, I have no doubt you can "Feel" the difference. Perhaps you'd like to take me up by participating in my blind crank length experiment. Let me know and I'll set it up. The cost is a case of beer and a result made public here on The Hub. But now that I'm talking to you I just remembered something. You gave out some advice regarding 1,8mm spokes somewhere but ignored my question. Please let us know why 2mm spokes are stronger than 1,8mm spokes as you suggested. Oh, and why not tell us how you arrived at the proper crank length for your particular anatomical needs? We're all ears. Johan Bornman2008-09-01 14:46:38 Link to comment Share on other sites More sharing options...
Weekend_Warrior Posted September 1, 2008 Share Link to comment Share on other sites More sharing options...
Johan Bornman Posted September 1, 2008 Share Has anyone with a powermeter compared different length crank arms? Pleeeease... so this "feel" thing can be put to rest. Power is generated by the muscles in your body. The crank is just a linkage to your body and altering it's length (within reason) does not influence the body's ability to put out X amount of power. A longer crank allows you to generate more torque with the same pedal pressure, but then you have to drag that smaller amount of torque around a larger circle. What you score on the one side, you pay for on the other. When I was a little boy, my younger brother was scolded by my father for carrying too much stuff in one trip in one or other chore my father set him up with. My dad's words were that a lazy person will burden himself to the point of injury. My brother retorted that a dilligent person will walk himself to death. This argument is valid in the longer/shorter crank debate. Power is work over time and the only way to increase it is to either do more work in the same time, do the same work in less time or both. A longer crank makes your load easier but distance longer. Unfortunately the variances are so small that it will be difficult to measure with a power meter and we have to fall back to math. Johan Bornman2008-09-01 15:03:32 Link to comment Share on other sites More sharing options...
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