Slave Posted June 22, 2009 Posted June 22, 2009 I read this article on crank length and it got me thinking. It has been recommended that I run longer cranks given my height, but it has never bothered me before. (Currently running 170mm cranks, Height 1.9m) Gearing: Up front 52/42, rear, 11/21, nine speed. The atricle states, quite correctly that it will save some energy because of the longer "lever" to turn the pedals. It also states however, that a longer circumference is needed for the leg to comlete one revolution, therefore there is no conclusive evidenceof energy saving. I'd like to hear your opinions on this one.
GreyOwl3.0 Posted June 22, 2009 Posted June 22, 2009 Who was it who said "give me a lever big enough and I will move the world"??Probably some Greek mathematician... But I do know who said, "In the Alps I run a 180mm crank because it helps me climb better" Herr Ulrich knows a thing or two about bikes Slave, and when faced with a 6hour assault over 4 Alpine monsters, crank length plays a big part in power transfer, efficiency and recovery...and Ulli would know! For myself, I know that depending on the track I'm racing I ride either a 165mm crank, or a 170mm. Its easier to accelerate the shorter crank from slower speeds, and easier to spin the gear. Racing on the road, I ride a 172.5mm because I can still 'spin' my gears, but find it a little more difficult to do so on a 175mm crank. But if I was to race a big mountain event like the Jock, I'd ride a 175mm without even hesitating. I'm not sure on the science of it all, but I do know what works for me...and crank length makes a big difference.I've said for a while that your cranks are too short...you need a 175mm. My 2c...
obree Posted June 22, 2009 Posted June 22, 2009 This has been discussed many times before, it depends on whether you are a fun rider or serious racer. Fun rider - longer will make no difference at all. Racer - 1% imrovement can be the difference between winning or not. I am 1.9m and use 200mm cranks, road and track, I can spin at 108 for an hour on the IDT, so no problem with spinning as many will say.
Slave Posted June 22, 2009 Author Posted June 22, 2009 ShawnA, Greyowl shares the same opinion as you do. I thought it might be wise to get several opinions on this one before I make any decisions. After my first ride in SBR, I was told I needed to go for a 52/39 chain ring and that experiment just hurt me. Not too keen to experiment and just have more pain. I will wigh up the options but am leaning towards longer cranks given my current gearing setup. I figure it can only help to do more of the reserve seated.
obree Posted June 22, 2009 Posted June 22, 2009 try zinncycling.com lenard Zinn is almost 2m tall race for USA national team, coached by Eddie B, so he knows a thing or 2. There is info there on calculating crank length
Slave Posted June 22, 2009 Author Posted June 22, 2009 The article appears here: http://www.bicycling.co.za/articles/handbook/the_fix/2573 Didn't see a formula for calculating crank length though.
GreyOwl3.0 Posted June 22, 2009 Posted June 22, 2009 200mm cranks Obree? Fark! Thats long! What gear do you run on the track with that? Minimum 104?!
obree Posted June 22, 2009 Posted June 22, 2009 200mm cranks Obree? Fark! Thats long! What gear do you run on the track with that? Minimum 104?! As you know I stay at the bottom for the pursuit, 97 - pedalling at 109rpm
Johan Bornman Posted June 22, 2009 Posted June 22, 2009 Total height has very little to do with your perfect crank length. Some tall people have short lets and vice versa. Crank length is a function of your femur length. If you run up stairs three at a time, you have longer femurs than 99% of the population and long cranks are right for you. 170-175mm cranks are fine for most of us. In fact, the right crank is the one that came with the bike. Finish and klaar.
Speed Devil Posted June 22, 2009 Posted June 22, 2009 I used to have 175mm cranks on my old 9 spd gruppo. When I upgraded to 10spd I noticed only after a few months that the new cranks were 172,5mm. During that time I never noticed any changes/differences in my pedalling.If I was you I would stay with the 170mm crank and just put a 39T blade on. It's much cheaper than replacing the whole crank to gain 2,5mm. Besides, if you got an 11/21 at the back then a 39T up front would be a better option.
Harryn Posted June 22, 2009 Posted June 22, 2009 beginner's question. How do you measure the crank? is is from the mid point of the nut to the end or from end to end? when I measure mine it gives me 200 - but that just cant be right.
porky Posted June 22, 2009 Posted June 22, 2009 (Currently running 170mm cranks' date=' Height 1.9m) Gearing: Up front 52/42, rear, 11/21, nine speed. I'd like to hear your opinions on this one.[/quote'] I like Mr Bornmans option, the cranks on your bike are the right one's.! ................but an 11/21 up SBR......................???? I dunno, I am certainly no fundi on gearing, but (I mean this in the nicest possible way slave) us oldies really need a 12/24 or 25 at the back, dont ya think thats maybe your problem? Hey, I dont know much on the technical issues, but I know I wouldnt be a cheefull fella going up SBR in a 21.!
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