crank arm lengths

[Profpointy]

I think I see where your confusion lies. 50% of people have one leg shorter than the other. The remaining 50% have one leg longer than the other.

And of course, most people have more than the average number of legs

 

[ColinJ]

And of course, most people have more than the average number of legs

I was discussing that in relation to national income levels yesterday. The fact that the average income in the UK is £2x,xxx disguises the reality that most people are on less than that, but the average is skewed by the multi-billionaires hanging out in London. The average number of legs is 1.xxxx, but the median number would be 2.

 

[jazzkat]

I have the median number of legs.
I have cranks of 170, 172.5 and 175mm on three different bikes and I can't tell the difference between them.

 

[ColinJ]

I have the median number of legs.
I have cranks of 170, 172.5 and 175mm on three different bikes and I can't tell the difference between them.

I am going to buy a triple chainset from Spa Cycles next week and I have a choice of those three crank lengths, depending on what combination of chainrings I want.

I think I will probably go for the 170 mm cranks because I fancy the 50/40/30 rings and they only have that length in stock.

172.5 mm cranks with 48/38/28 rings is my other favoured option.

 

[jazzkat]

I am going to buy a triple chainset from Spa Cycles next week and I have a choice of those three crank lengths, depending on what combination of chainrings I want.

I think I will probably go for the 170 mm cranks because I fancy the 50/40/30 rings and they only have that length in stock.

172.5 mm cranks with 48/38/28 rings is my other favoured option.

I doubt you'd notice a difference really, Colin.
I've 175mm on my mtb and tourer and 170mm on my fixed. I've ridden my fixed on a 100inch gear on the road (by mistake!) and didn't really notice a lack of leverage, though it was hard work. I know it's all to do with femur length, but past that, to quote a certain waiter, "I knowa nothing"

 

[Ajax Bay]

Thread resurrection, but it's been raised separately.
This seems a pretty well constructed article:
http://bikedynamics.co.uk/FitGuidecranks.htm

 

[Heisenberg71]

Interesting piece on GCN recently in relation to crank length.
They conclude that shorter riders would benefit from shorter cranks. Not de facto, but interesting.


View: http://youtu.be/eMAxH_Ud8YE

 

[Ajax Bay]

Thank you for sharing, @Heisenberg71, I like many of their (GCN) videos but this was a below average one imho. Could have been interesting but undermined by pretty poor science (one rider 6' tall, one power level (330w(!)) and the sprint test was, as they then admit, flawed by failure to change to the best gear (162.5 > 177.5 delta is ~9% extra leverage) - why didn't they take the trouble to reshoot? (My answer: because they knew the topic was going to be difficult to 'treat' in tests which needed condensing into their 8 minute video format so they cut their losses). At the end pulls arbitrary conclusions out of the bag (shorter would benefit shorter, helps with 'injury problems', better aero). Probably all true, but based on nothing in the video. Whereas http://bikedynamics.co.uk/FitGuidecranks.htm what did you think?

 

[Heisenberg71]

As I said, the GCN piece is "not de facto, but interesting".
Having read the article in full, it seems very comprehensive and compelling.

However my personal opinion is it makes knack all difference that the average cyclist can notice. I am 5'8" with a 32" inside leg (pretty short really). I run 172.5mm cranks and the article would recommend I run 170mm. Would I, Mr Average cyclist really notice the 2.5mm difference? I might, but I am not convinced to the degree I want to spend £250 on a new set of SRAM Red carbon crank arms to find out. I don't suffer bike related pain. My knee can hurt sometimes on long rides with massive climbs. In the main I am fine for what I do.

A very thorough study though with much better argued conclusions than GCN.