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Crankset 172.5 or 175 mm?(9 posts)

Crankset 172.5 or 175 mm?RaiderMike
Nov 24, 2001 10:11 PM
I am building my first road bike and have heard that I should run a 172.5mm crankset as opposed to the 175mm that I have on my mountain bike. I am tall at 6'4" and have no problem spinning efficiently on my mountain bike with the 175's. I also ride about 50/50 climbing and flats so it is a toss up their. Is it just personal preference? I would greatly appreciate any theories, or opinions.
re: theories and opinions abound...Akirasho
Nov 24, 2001 10:34 PM
... there has been a lot of debate on the forums about crankarm lengths... relatively few and small increments in sizes vs. a wide variety of leg lengths and cycling styles (you can search these forums for more info)...

Still, I'd have to say, conventional wisdom would put someone of your height (and assumed leg length) on the longer cranks...

I'm 6'2" with a 37" inseam and run 175mm on both road and MTB... but I recently came across a pair of Dura Ace cranks and during a side by side comparison, was amazed at how little a difference that 2.5mm is (as a static measurment). I've yet to use the crankarms... so I can't tell you how they feel.

Go with the longer and use the extra leverage... either for power or an easier spin... eventually, efficiency will rest in your technique.

We abide.

Remain In Light.
It really is preference.Sintesi
Nov 26, 2001 12:03 PM
Conventional wisdom would put you with 175 or larger. I remember reading an article once where a guy accidentally installed 175s on one side and 172.5s on the other of his tandem and never noticed for the better part of the year. And he only found out about it when he pulled the cranks to work on his bb. For what its worth, Lance uses 175 cranks and I think he's 5' 10".
Crankset Power Testbiker duder
Nov 26, 2001 5:19 PM
Check out article at VeloNews:
Big Mig used 180's.breck
Nov 26, 2001 7:46 PM
"In the early days we never knew that Miguel had such a large 'motor' and we didn't bother changing things like the length of his cranks much until he won his first Paris-Nice in 1989. As an amateur he rode with 172.5mm cranks, then in his first year as a pro (late 1984-1985), it went down to 170. Gradually after that they got longer, first going to 175, then to 177.5, and finally to 180."
-Enrique Sanz

Cycle Sport
March 1997 (UK issue)
"Indurain, the Life and Times of a Tour Superstar"

I use 175mm on the Mtb bike & also on the road bike ridden here in the mountains for the same reason ...more leverage on the climbs.

"Spinning on the mountain bike" ???
When and for how long?
You must have sum very long and straight trails.

San Diego bgcc
Nov 27, 2001 2:35 PM
I ride a 30 mile round trip to get to my trails so I do my share of spinning
re: Crankset 172.5 or 175 mm?grzy
Nov 27, 2001 4:14 PM
At 6'4" one must assume that you have longish legs. Ultimately you should favor running longer crank arms. 172.5 is deriguer for average sized people - run at least a 175. You ay want to go longer but you should think about this carefully - you run a higher risk of striking the ground if you pedal through the corners. I have a bud who is 6'5" and runs 180's - he says it just feels more comfortable over long distances.
re: Crankset 172.5 or 175 mm? Try the 180s.Lovehamr
Nov 28, 2001 6:54 AM
I tend to agree with the longer is better approach. I'm 6'2" and use 180s on everything, road, mountain, dual suspension, and single speed. I tried it on the second bike I built and couldn't believe the extra power that I seemed to have. Now understand that my cadence is slow but has alot of power, this may be why the 180s fit me so well. At your height you may want to go ahead and take the plunge and try a set of 180s. Hey if you don't like them, you could always sell them here. Just my humble opinion.
re: Crankset 172.5 or 175 mm?mclements
Nov 29, 2001 5:37 PM
Power is equal to torque multiplied by RPM (cadence). In other words, the product of how hard you're pushing, with how fast you're spinning.

Longer cranks give you more torque, but less RPM because your legs must move a greater distance with every revolution.

Shorter cranks give you less torque, but more RPM.

In the end, which gives the highest overall power output will depend on the individual. Personally, I think these differences are overrated; I don't notice any significant difference between 170s and 175s.