Crank arm Length

glasgowbhoy

I bought another chainset recently and forgot to ask the size on it. It turns out to be a 170.

On my racing bike I have 175's and on a TT bike 172.5's . To be honest I've not really noticed the difference but going from 175 to 170 on my race bike is it likely to be more noticable? I'm about 178cm and would say I'm longer in the legs than the torso. I have had comments when racing that I do look like I'm riding a bit 'over geared', so, would shorter cranks and poentially more spinning be a good thing?

owenlars

Here is what the very wise Sheldon Brown has to say on the subject.
http://sheldonbrown.com/cranks.html

glasgowbhoy

Will fit them and see how I go then, cheers for the link

ric/rstsport

If you're overgeared why not (if you think it's important to you) just gear down.

Crank length doesn't have any effect on performance. Just select the cranks that allow you to get in the best position.

Ric

racingcondor

The biggest problem is probably that you'll have to add 5mm of spacers under your stem and 5mm to the seat post to get the same leg extension at the bottom of your pedal stroke. Not necessarily a big problem but it can take some fiddling to get your head around the fit implications (depending on tube angles etc between frames).

Now that I'm used to is I barely notice the move from 172.5 on the road bike to 165 on the track bike. I wouldn't worry about the crank length too much, you'll have a bit of time adapting but probably not long.

mrwibble

shorter lengths seem to work well for a TT bikes with what I have researched, longer cranks for road bikes, good for climbing and longer legs

mrwibble

and some one else will say the opposite, so personal preference. I read somewhere shorter crank length for TT helps open the hip angle which sounded logical.

BenderRodriguez

Ric/RSTSport wrote:

Crank length doesn't have any effect on performance.

Whilst I would tend to agree that whether you use 175mm cranks or 170mm cranks is if no real consequence, surely there must be a limit to this? Suppose I had a set of 100mm cranks made up, and a set of 200mm cranks, would there really be no effect on performance if I swapped between them?

mrwibble

TT'ing requires an high cadence to set fast time so if you are used to fast spinning then a shorter crank means the circumference distance is shorter for the pedaling?

Grill

Shorter cranks on TT bikes. Besides that preference is key.

mrwibble

@grill
what's your Foil 20 like? What is the stiffness like, too much?

Grill

mrwibble wrote:

@grill
what's your Foil 20 like? What is the stiffness like, too much?

Fantastic bike (I've had 2). Plenty comfy for me as it's now been relegated to my winter bike. Done loads of audaxes on it, including 400k and 600k.