Road Bike, Cycling Forums banner
1 - 5 of 5 Posts

· Registered
Joined
·
3 Posts
Discussion Starter · #1 ·
I recently bought a 2010 model 105 5700 group set that I installed to my Trek 1.9. I opted to install a 175 mm crank set, though i my previous crank set was an FSA with 172.25 mm in length. I opted on that 175 mm due to that fact that I prefer to get that extra power on climb rides. But I heard that the 175 mm crank set may not be convenient when it comes to long flat rides, especially on a faster speed. It is okay for me considering that my height is 5'-8"?

Thanks a lot in advance!
 

· Registered
Joined
·
11,555 Posts
Some info.

dongkg said:
I opted on that 175 mm due to that fact that I prefer to get that extra power on climb rides. But I heard that the 175 mm crank set may not be convenient when it comes to long flat rides, especially on a faster speed. It is okay for me considering that my height is 5'-8"?
The 2.5 mm difference between the cranks is so small that it doesn't matter. In addition, there's no proven connection between crank length and power (power = the rate of doing work), so the difference doesn't matter in that department either. Conventional wisdom has it that at 5'- 8", the rider should be on a 170 mm crank. But there's nothing wrong with trying 175 mm cranks and see how you feel. IMO, what is important is to ultimately pick a crank length and stick with it so the body can adapt to it.

I've never heard of longer cranks not being "convenient" for long flat rides. Perhaps it has something to do with the belief that longer cranks are harder to spin than shorter ones. But even that turns out to be a bit of unclear thinking: longer cranks simply produce a longer crank circle. So at the same leg speed, it just takes a little longer to complete one circle ("1 rpm") than it would with a shorter crank. Why that would "not be convenient" I don't know. If you want your old cadences back, just train to increase leg speed slightly with the longer cranks.
 

· Registered
Joined
·
79 Posts
+/-2.5mm is a very small change in length, around 1.5% difference. You may notice it, but it is pretty subtle. I ride the three common lengths (170, 172.5, 175) on three different road bikes without issue. I find them all equally 'convenient' on flat or hilly rides-the length difference between them is really quite insignificant. Ride it and see how you like it.
 

· Premium Member
Joined
·
20,696 Posts
darkmother said:
+/-2.5mm is a very small change in length, around 1.5% difference. You may notice it, but it is pretty subtle. I ride the three common lengths (170, 172.5, 175) on three different road bikes without issue. I find them all equally 'convenient' on flat or hilly rides-the length difference between them is really quite insignificant. Ride it and see how you like it.

+1....I mistakenly installed a 172.5mm arm on the non-drive side of a 170mm crank..I rode it that way for a year before I realized it.......
 

· Registered
Joined
·
3 Posts
Discussion Starter · #5 ·
Thanks a lot for the comments and observations of these differences on the crack set's length. Hopefully, I will ride my roady this weekend and try to see the difference, if any. We intend to ride for around 120 kms., back and forth.

thanks a lot again...

This Forum is very informative...
 
1 - 5 of 5 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top