Crank length!

[Roreh says:]

I ride 180mm cranks.

I have a 1m inside leg and size 15 feet.

What crank length would you suggest?
So far I have stuck with 180mm as the are the longest readily available cranks I can get.

I do however have one pair of 185mm cranks which were on my time trial bike, and I was getting appauling times compared to what I could do in a group on my race bike. But then I swapped it's cranks over to 180mm and I knocked 1:30 minutes off my 16km time trial personal best!

So this is what has got me confused. Was I slower on the 185mm cranks because I did ALL my training on 180mm cranks and I simply wasnt used to 185mms or are 185mms simply to long for me?

Thanks for any thought in advance.

 

[Look381i]

Originally posted by Roreh says:
I ride 180mm cranks.

I have a 1m inside leg and size 15 feet.

What crank length would you suggest?
So far I have stuck with 180mm as the are the longest readily available cranks I can get.

I do however have one pair of 185mm cranks which were on my time trial bike, and I was getting appauling times compared to what I could do in a group on my race bike. But then I swapped it's cranks over to 180mm and I knocked 1:30 minutes off my 16km time trial personal best!

So this is what has got me confused. Was I slower on the 185mm cranks because I did ALL my training on 180mm cranks and I simply wasnt used to 185mms or are 185mms simply to long for me?

Thanks for any thought in advance.

----Perhaps there is a difference because of your long inseam, but I read recently that studies of the same riders at various cranklengths (170, 172.5, 175) revealed no efficiency differences.
I neglected to note the citation of the reference. I suspect extremely wrong lengths would make a difference, though.

 

[Vector7]

Originally posted by Roreh says:
I ride 180mm cranks.

I have a 1m inside leg and size 15 feet.

What crank length would you suggest?
So far I have stuck with 180mm as the are the longest readily available cranks I can get.

I do however have one pair of 185mm cranks which were on my time trial bike, and I was getting appauling times compared to what I could do in a group on my race bike. But then I swapped it's cranks over to 180mm and I knocked 1:30 minutes off my 16km time trial personal best!

So this is what has got me confused. Was I slower on the 185mm cranks because I did ALL my training on 180mm cranks and I simply wasnt used to 185mms or are 185mms simply to long for me?

Thanks for any thought in advance.

One thing to consider is that the size of your crank will effect your cadence...even if so slightly. One way to compensate for the longer crank length is to play with your cassett. What are you currently riding? One thing that taller riders on our team do is go with a bigger cassette as the crank length increases. It keeps your cadence up and gives you the power to muscle the bike forward at a descent rate. The RPM's also stay up in a healthy range where you're not straining on every pedal. I hope this helps.

Best Wishes,
Vector7

 

[retrogeek]

You should go to the thread:

Poll: Crank Length

Started by Steve, and it is in this section (Cycling Equipment). A very good in-depth discussion about crank length.

Also, go to Google and type "Crank Length" in the search field and you will get a number of sources to read up on. These two sources will be a good place to start in helping you to better understand your question.

Your question is not easily answered without knowing other variables such as riding style, general bike and pedal setup, your position on the bike, your physical makeup, etc.. But try reading the material cited above and see if that doesn't narrow down your list of questions and eliminate some of the variables you are experiencing. I would hesitate giving you any advice based on just an inseam measurement and foot size.

Ultimately though it is what you ride the fastest on that really matters, not what a bunch of theories and formulas say you should use. Cycling history has shown this time and again.

Good luck!