Shorter crank length as you age?
06-05-19, 10:03 PM
#51
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Radius is only half the picture. You have to address the total diameter. So a 5 mm change in crank length means your stroke is 10 mm more, which is .394" or a little more than 3/8ths inch.
Surprisingly for me, the difference was noticeable when I went from 165 mm to 170 mm cranks. YRMV.
As for those that think shorter cranks mean harder pedaling, then they are forgetting to shift down to a lower ratio gear combo.
Since I'm a road bike type and do get in the drops fairly often, I don't need my knees driven an inch further into my chest by using the 190 mm cranks. I'll keep my 165's and be assured that I can pedal while turning without hitting the pavement.
So to me, it still gets back to whether you want to be a masher or a spinner. No formula needed.
Surprisingly for me, the difference was noticeable when I went from 165 mm to 170 mm cranks. YRMV.
As for those that think shorter cranks mean harder pedaling, then they are forgetting to shift down to a lower ratio gear combo.
Since I'm a road bike type and do get in the drops fairly often, I don't need my knees driven an inch further into my chest by using the 190 mm cranks. I'll keep my 165's and be assured that I can pedal while turning without hitting the pavement.
So to me, it still gets back to whether you want to be a masher or a spinner. No formula needed.
What really limits us - relative to the difficulty of exertion - is the power requirement. Which is the same for either crank length. Neither this, or the cadence as a lot of people think, are really considerations for or against changing the crank length. It's more about, perhaps only about, the change in the range of motion.
08-08-19, 12:26 PM
#52
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Benefits of longer cranks?
I'm curious about going the other way. It seems to me that the longer crank gives slightly more leverage on the pedal for a given gear. I switched bikes a few years ago and started having knee issues. I noticed that my previous bikes all had 172.5 and 175mm cranks whereas my new bike has 170. I recently put one of said old bikes on a trainer and found pedaling to feel more comfortable... So, here's my question: Everyone toutes the benefits of going to a shorter crank, am I crazy for wanting to go longer?
Some stats on me:
5'9"
32" inseam
current go to bike: Salsa Vaya 54 (170 cranks)
trainer bike: Cannondale Synapse 56 (172.5 cranks)
And I should note that I mostly ride with loaded panniers on, so I'm hauling some mass up the hills.
Some stats on me:
5'9"
32" inseam
current go to bike: Salsa Vaya 54 (170 cranks)
trainer bike: Cannondale Synapse 56 (172.5 cranks)
And I should note that I mostly ride with loaded panniers on, so I'm hauling some mass up the hills.
08-08-19, 01:14 PM
#53
Senior Member
I think there are three instances in which shorter cranks can help:
1. if you're short and have short legs.
2. if you have a knee replacement and as a result have less range of motion.
3. if you have poor pedaling technique and tend to put maximal pressure on your pedals, at the top of the stroke.
Of course, "personal preference" trumps all of the above. Bear in mind that most people who get shorter cranks also get lower gears and spin more. It's part of the power equation.
1. if you're short and have short legs.
2. if you have a knee replacement and as a result have less range of motion.
3. if you have poor pedaling technique and tend to put maximal pressure on your pedals, at the top of the stroke.
Of course, "personal preference" trumps all of the above. Bear in mind that most people who get shorter cranks also get lower gears and spin more. It's part of the power equation.
08-08-19, 03:07 PM
#54
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My 51 year old knees seem to like 170 or 172.5 cranks. 165 feels too small, 175 to 180 leave my knees sore. This is taking proper saddle height and placement well into consideration. I am 5' 10" with a 33" inseam (short torso).
08-09-19, 11:11 AM
#55
Senior Member
I've never tried, but I suspect you're right that going from 170 to 165 would be barely noticeable. Going 'short' is pretty common in the recumbent world; but it usually means going from 170 to 153. That results in something like 11% difference in force at the pedals, and yes that is definitely noticeable. Especially when you encounter a hill that puts you into your lowest gear and you've got 11% less torque to work with. My shorty experiment ended after walking one hill that should have otherwise been do-able in 2nd or 3rd.
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