Is there any benefit from Crank lengths for the average Joe

tonysj

Hi All,

I've been road cycling for around 18 months and really enjoy everything about it.
Ive had a bike fit on my summer bike and transfered the measurments to my winter bike so they are as close to the same as I can get.
Question is I'm 5'10", and 32" inside leg in trousers ( not sure of any bike related inside leg measurment! ), now both my bikes have 175mm cranks and brousing the net I've noticed that manufacturers generally fit 175mm to XL or the bigger sized frames so I'm wondering are the 175mm cranks likely to limit my ability in some way?
It may seem a dumb question but its something Ive never looked into so Im asking the knowledgeable members on this forum to give me some info that may give me an idea of if I need to change them to help me.

Thanks.

Tony.

bristolpete

Worth a read here bud.

http://bikedynamics.co.uk/FitGuidecranks.htm

StillGoing

TonySJ wrote:

Hi All,

I've been road cycling for around 18 months and really enjoy everything about it.
Ive had a bike fit on my summer bike and transfered the measurments to my winter bike so they are as close to the same as I can get.
Question is I'm 5'10", and 32" inside leg in trousers ( not sure of any bike related inside leg measurment! ), now both my bikes have 175mm cranks and brousing the net I've noticed that manufacturers generally fit 175mm to XL or the bigger sized frames so I'm wondering are the 175mm cranks likely to limit my ability in some way?
It may seem a dumb question but its something Ive never looked into so Im asking the knowledgeable members on this forum to give me some info that may give me an idea of if I need to change them to help me.

Thanks.

Tony.

The search engine is your friend. Its been covered umpteen times on here. You'll have the camp that say it makes no difference and the camp that says it does. Only you can decide.

svetty

Advocates of both shorter and longer cranks will persuasively and stridently assert their view. IMO both are Cranks.
The thing that limits most people is aerobic function I.e. watts not crank length.

Matthewfalle

No.

imposter2.0

This is an interesting read: http://myworldfromabicycle.blogspot.co. ... -just.html

gsk82

I got a big benefit on my tt bike. A 5mm shorter crank gives an extra 10mm of room at the top of the pedal stroke ie less cramped up. Its more a comfort thing than a power theory thing though.

timmyotool

I moved from 172.5/170 to 165mm cranks after doing some reading around it. I have a 31 inch leg.
I used to have pain/tiredness in my hip flexors during a ride, this definitely helped.
When I go back to longer cranks I definitely notice it feels different, but I can't say I noticed any performance benefit either way.

cycleclinic

That is the way shorter cranks can help. While in top or hood position crank length makes little difference to me on a few bikes where I am low on the drops shorter cranks help.

Poppa Wheelie

I'd say that if you are NOT the average Joe it makes a difference.

If you are of average height I'd expect you'd not really be to tell much difference between different length cranks but if you are really tall or short it does make a difference.

The amount of force you apply to your back wheel through the chain depends on the length of the lever (pedal crank arm). The longer the lever the more force you apply through to your back wheel for the same amount of force applied to the pedal.

If the lever/pedal crank is too short then you are not applying the optimum amount of force to the chain/wheel.

Equally if the pedal crank is too long then the foot at the top of the pedal stroke will be too high for you to push down effectively. Remember, your seat height is based on your leg extension at the bottom of the pedal stroke, your pedal crank length affects the position of your leg at the top of the stroke. If the pedal crank was really long your heel would be almost touching your buttock and you would barely be able to push down on the pedal.

I doubt anyone would argue that the height of each step in a flight of stairs needs to be within a certain range. If each step was too low then they are awkwardly easy to climb and if each step was really high, like two or three normal steps high, then it would also be really hard to push yourself up each step. The same analogy can be applied to pedal cranks.

If you are shorter than average you'll benefit from a shorter crank and if you are really tall you'd benefit from a longer crank. I think anyone can ride any crank length for a short duration but after 50 miles you'd appreciate the correct length crank for your leg length.

(It's worth pointing out that the longer the pedal crank, the further your foot travels which will affect the cadence you can turn the pedals at).

Andymaxy

Say that there maybe a benefit for going shorter, given that you have ridden 175 for 18 months, your body will take time to get used to shorter cranks, so I think for quite a while you will still be able to produce more power on 175 than whatever shorter cranks you are looking at.

In my case I've got 31.5 inseam and used 172.5 previously. Not too long ago I switched to 170, and they make me feel more comfortable on the bike for sure. However, I don't think there is any difference in power.

SHHH

I ride my TT setup (long distance) for most of the year and find that shorter cranks definitely feels better at the top. Went from 170mm to 165mm. If I was given a choice I'd have 165 on all my bikes, or even a 162.5 which I've never tried. But I'm a small rider.

kleinstroker

Doesn't changing crank length also change seat height and therefore drop/reach to bars?
Have tried all the combos from 170mm to 175mm and cannot quantify the difference to make a "right" choice , they all feel ok tbh

amrushton

Seat height is altered. A 5mm shorter crank means you will need to raise the seat by 5mm or near to. Your foot will of course always describe a smaller circle using shorter cranks (pi x d) so your cadence will raise lightly. This may suit people who prefer a higher cadence. Subject to position you may also find the hip angle opens up more.