Cranks Length?

mickmcl09

I'm currently using 172.5 cranks.
5'9'' tall and inseam of just over 30''.
I was looking at the sample download on www.IrishFit.ie and realise that I'm borderline for going down to a 170 crank.

Has anybody here had to change downwards?
How was your performance affected?

Regarding my current set-up, I find it very comfortable until it comes to sprinting and the cadence figures go above 125+, at that point I can feel that extra 5cm gap from the top to the bottom of the pedal stroke, would this indicate that I'm using cranks that are too long?

C3PO

I think it's actually only 2.5mm(not cm) difference?

SurferDude41

I am 5' 10" Or in Euro nonsense 178cm
Have a 31 inch inseam. I use 172.5 cranks, my saddle height is 73.4 cm
I have been using the 172.5 cranks for years, without a problem.
A few years ago I tried 175mm cranks, My cadence began to suffer. Indeed I had no acceleration, and my legs felt really weird:eek:
Needless to say I changed back to 172.5 cranks, straight away.

You might benefit by reducing to 170mm cranks.
And your knee ankle and hip joints, may thank you as well:)
As your feet are 5mm closer together on the shorter crankarms.

Try to borrow a clubmates chainset, just for one day at least. It should give you a fair idea, how your body responds to using shorter cranks.

Sean Kelly uses 172.5 Stephen Roche 170 Lance Armstrong 175
Tom Boonen 177.5 Mark cavendish is on 170

Hope this helps.

Happy Cycling:)

Lumen

If you're spinning out a 53/11 at 125rpm the discomfort is probably due to the fact that you're putting out more power than Cavendish.

2.5mm is not a big deal. If you had shorter cranks you'd just have to put out more torque.

bcmf

SurferDude41 wrote: »

I am 5' 10" Or in Euro nonsense 178cm


Sean Kelly uses 172.5 Stephen Roche 170 Lance Armstrong 175
Tom Boonen 177.5 Mark cavendish is on 170

..... and Pantani rode 180.

but I suppose 'upstairs' he was a few cm's short of the metre so it kinda balanced out

C3PO

Most of the stuff I've read on crank length seems to suggest that the difference 2.5mm makes is really marginal! And there seems to be even less agreement about what crank length is optimal anyway! Saddle height and fore/aft position, stem length and bar height seem to be much more important variables.
I'm 5'10"ish and both of my road bikes have 170mm cranks (that's what they came with!) but my mountain bikes are 175mm (because that's what just about everybody uses on mtbs regardless of leg length!). Maybe if I need to replace the cranks on my road bike I might upgrade to 172.5mm but I'm not losing any sleep about it!

dave2pvd

Lumen wrote: »

If you're spinning out a 53/11 at 125rpm the discomfort is probably due to the fact that you're putting out more power than Cavendish.

2.5mm is not a big deal. If you had shorter cranks you'd just have to put out more torque.

Or you'd use the next smallest gear. To maintain a given torque at the wheel.

For the record: 6'1.5", 33" inseam, 172.5mm cranks.

Lumen

dave2pvd wrote: »

Or you'd use the next smallest gear. To maintain a given torque at the wheel.

...except the OP is spinning out his smallest cog at 125rpm

dave2pvd

Lumen wrote: »

...except the OP is spinning out his smallest cog at 125rpm

mickmcl09

Lumen wrote: »

If you're spinning out a 53/11 at 125rpm the discomfort is probably due to the fact that you're putting out more power than Cavendish.

2.5mm is not a big deal. If you had shorter cranks you'd just have to put out more torque.

I wish I could push 53/11....wishful thinking.....I was just talking about cadence and relative comfort at a high level of cadence. I'm going to try the 170 for a month and see if it makes a difference.

Thanks lads.