erhan
04-15-05, 03:08 AM
Just wondering, does it really worth to get a $400 crankset to save 300 grams? would it make that much difference?
View Full Version : light cranksets?
antoine
04-15-05, 03:23 AM
300 grams is huge on a bike, well, depends on what type of riding you do and what type of bike you have. However, a lighter crancks means a faster spinning at "sprint" time (if you got the legs for it though)
capsicum
04-15-05, 04:18 AM
300 grams is huge on a bike, well, depends on what type of riding you do and what type of bike you have. However, a lighter crancks means a faster spinning at "sprint" time (if you got the legs for it though)
No it dosen't, the laws of physics say so.
No it dosen't, the laws of physics say so.
erhan
04-15-05, 12:25 PM
the laws of physics say so.
could you explain?
what type of riding you do and what type of bike you have.
I have a 23 lbs. xc hardtail and I like to go as fast as I can. I am not ready to race but I will be in a few months I guess. So, I'm trying to get the bike as much "race ready" as possible.
So, is it going to be like having a lighter wheels? Faster acceleration?
could you explain?
what type of riding you do and what type of bike you have.
I have a 23 lbs. xc hardtail and I like to go as fast as I can. I am not ready to race but I will be in a few months I guess. So, I'm trying to get the bike as much "race ready" as possible.
So, is it going to be like having a lighter wheels? Faster acceleration?
capsicum
04-16-05, 07:51 AM
No, it's not much more than plain old weight.
Cranks don't have enough total rotational speed, or change in rotational speed, for a noticeable change in rotational inertia, basically weight in the cranks is barely different than weight in the bottom of the frame.
I know people who race 26lb hardtails and do just fine, lighter cranks should be at the very bottom of your list, training at the top and just enering and attempting a race should be a close second.
Cranks don't have enough total rotational speed, or change in rotational speed, for a noticeable change in rotational inertia, basically weight in the cranks is barely different than weight in the bottom of the frame.
I know people who race 26lb hardtails and do just fine, lighter cranks should be at the very bottom of your list, training at the top and just enering and attempting a race should be a close second.
Weasel
04-20-05, 04:44 AM
However.........
I have just replaced my very old XT crankset and bottom bracket with a new XTR hollowtech 2 crankset ( with integrated bottom bracket), and it is not only 300+ grams lighter, but also VERY much stiffer. In my opinion it was well worth it, my bike weighs 9.8kgs (under 22lbs) and feels much better for it. It does not flex like it used to when standing up out of the saddle.
As for the physics - well I'm no physics teacher, but it makes a HELL of a difference. Hope that helps. :)
I have just replaced my very old XT crankset and bottom bracket with a new XTR hollowtech 2 crankset ( with integrated bottom bracket), and it is not only 300+ grams lighter, but also VERY much stiffer. In my opinion it was well worth it, my bike weighs 9.8kgs (under 22lbs) and feels much better for it. It does not flex like it used to when standing up out of the saddle.
As for the physics - well I'm no physics teacher, but it makes a HELL of a difference. Hope that helps. :)
alcahueteria
04-20-05, 10:29 PM
I think a lighter crank would make it easier to spin. It would decrease the moment of inertia (which is a function of mass) also known as rotational inertia. So I would think 300 grams would make a large difference, in the cranks atleast.
capsicum
04-21-05, 04:56 AM
I think a lighter crank would make it easier to spin.
No
It would decrease the moment of inertia (which is a function of mass) also known as rotational inertia.
Yes
So I would think 300 grams would make a large difference, in the cranks atleast.
No
The stiffness talked about would make a large difference in feel and that may have a real and or a mental effect that would cause a large real, or large imaginary, performance difference. But the difference in rotational inertia would be almost imperceptible by a rider, trouble is its not a double blind study so placebo effect can be a large factor.
No
It would decrease the moment of inertia (which is a function of mass) also known as rotational inertia.
Yes
So I would think 300 grams would make a large difference, in the cranks atleast.
No
The stiffness talked about would make a large difference in feel and that may have a real and or a mental effect that would cause a large real, or large imaginary, performance difference. But the difference in rotational inertia would be almost imperceptible by a rider, trouble is its not a double blind study so placebo effect can be a large factor.
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