Crank length - should I increase?

Pinch Flat

I am in the process of replacing my Campagnolo Athena crankset with the same spec. replacement

The cranks are 170mm. My winter bike has 175mm. Should I consider taking this opportunity to lengthen the campag cranks? I'm just shy of 6'2" and always felt my "good" bike was a tad small at 56cm. I've made some subtle improvements (longer angled Ritchey Stem has helped) and wonder would this subtle crank difference be noticeable?

triggermortis

Is it possible to swap the cranks you already have over to see if there is a noticeable difference?
Given your height, I'd say 175 might be more comfortable anyway

Pinch Flat

Thanks for the reply - should have explained 'good' bike is Campag, winter bike is Shimano. So swapping not an option.

Beasty

Whenever we have these discussions about crank lengths we get a variety of views. Many people seem to notice quite a difference. I ride 165 or 170 on the track and 175 on the road bikes, and honestly notice no difference at all. I have moved slightly longer on the track bike simply because I know it will give me slightly more leverage in a standing start situation.

Seweryn

Pinch Flat wrote: »

I am in the process of replacing my Campagnolo Athena crankset with the same spec. replacement

The cranks are 170mm. My winter bike has 175mm. Should I consider taking this opportunity to lengthen the campag cranks? I'm just shy of 6'2" and always felt my "good" bike was a tad small at 56cm. I've made some subtle improvements (longer angled Ritchey Stem has helped) and wonder would this subtle crank difference be noticeable?

It will be a very noticeable difference. 5mm on a crank arm is a lot.

I used to cycle on 170mm (the bike originally came with 175mm cranks, but that felt horribly wrong to me, so I changed them immediately). Then I moved to 165mm over a year ago and now feel even better.

There are a lot of factors that should be considered like your leg length, you cadence preference, etc. Then there is your bike fit that will have to be changed to accommodate the new crank arm length, i.e. the saddle position (horizontally and vertically), height of the handlebars as a result, and the stem length.

I personally prefer the shorter crank arms as they feel like being more efficient. This is due to the pedalling action being smoother, the force distribution more equal through the spinning cycle, and your cadence being higher (so you can use lower gears).

martyc5674

Seweryn wrote: »

This is due to the pedalling action being smoother, the force distribution more equal through the spinning cycle, and your cadence being higher (so you can use lower gears).[/QUOTE]

Surely that should read..."requiring you to use lower gears"
the reason you would have to use lower gears though is because you have less leverage with the smaller crankarm...so youll still feel the same pressure through your legs albeit by spinning a smaller circle.

Seweryn

martyc5674 wrote: »

Surely that should read..."requiring you to use lower gears"
the reason you would have to use lower gears though is because you have less leverage with the smaller crankarm...so youll still feel the same pressure through your legs albeit by spinning a smaller circle.

Generally yes...

The full leverage only happens when the cranks are horizontally positioned and the difference is still less than 3% between 170 and 175mm cranks. In other crank angles, the longer cranks get lower force applied because of the compromised position on the saddle (lower) and less advantageous knee angles (too tight angles when the pedals are in top position). So you phisically are unable to apply the same force with longer cranks.

Another positive is that there is less pressure on your knees with shorter cranks.

martyc5674

My new bike will have slightly shorter crank arms than im "used to".(going from 172.5 -> 170 )
Im hoping they will be kinder to my knees for exactly the reasons you mention in your last post
Initially i thought they might be harder on my knees having less leverage.
Marty

Seweryn

martyc5674 wrote: »

My new bike will have slightly shorter crank arms than im "used to".(going from 172.5 -> 170 )
Im hoping they will be kinder to my knees for exactly the reasons you mention in your last post
Initially i thought they might be harder on my knees having less leverage.
Marty

The shorter cranks will be kinder to your knees Marty. The main reason is that your knees will never bend as much as with longer cranks.

It is good to avoid an angle below, say 70 degrees (the minimum knee angle) as this can put high shear forces into your knee joint, exaggerates the dead zone at the top of the pedal stroke and may cause discomfort in the hip and lower back...