rhafe
12-03-02, 07:48 AM
What are the advantages/disadvantages of longer cranks. I have 180mm on my bike and I guess that is longer than typical. Thanks
Road Cycling - Cranklength question
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palooka
12-03-02, 02:20 PM
I think it's mainly a height thing. Tall riders with longer legs want longer cranks, the opposite for short riders.
Also, and this may be completely false...I've heard the longer the crank, the better suited it is for climbing. The shorter the crank, the better for spinning.
Also, and this may be completely false...I've heard the longer the crank, the better suited it is for climbing. The shorter the crank, the better for spinning.
JohnnyFausto
12-03-02, 05:38 PM
All of my mountain bikes came with 175mm cranks and my road bike came with 170mm. I seem to be able to spin better on the road bike but that could be because of the design of the bike. It seems that the longer cranks would give me more leverage but I really don't know for sure.
abongon
12-03-02, 06:41 PM
\Longer arm means long lever and thats more pedal power good for uphill poor on sprint
just my own analysis no reference or reading I'm not sure about it but I guess I got a point for this
:D
just my own analysis no reference or reading I'm not sure about it but I guess I got a point for this
:D
pokey
12-03-02, 07:04 PM
Originally posted by abongon
\Longer arm means long lever and thats more pedal power good for uphill poor on sprint
just my own analysis no reference or reading I'm not sure about it but I guess I got a point for this
:D Longer is only good if you have the leg length and strength to use it. Alot of it has to to with the indivudal, and personal preference.
\Longer arm means long lever and thats more pedal power good for uphill poor on sprint
just my own analysis no reference or reading I'm not sure about it but I guess I got a point for this
:D Longer is only good if you have the leg length and strength to use it. Alot of it has to to with the indivudal, and personal preference.
John E
12-03-02, 07:14 PM
Sheldonbrown.com has some valid observations on this subject.
I wear a 30" trouser inseam and happily ride standard 170mm cranks.
I wear a 30" trouser inseam and happily ride standard 170mm cranks.
Poppaspoke
12-03-02, 07:15 PM
Bicycle Crank Length Calculator:
http://www.thankstomycranks.com/crankCalc.htm
This could give you a rough approximation. Keep in mind that riding style, femur length, knee problems, etc. play a role.
http://www.thankstomycranks.com/crankCalc.htm
This could give you a rough approximation. Keep in mind that riding style, femur length, knee problems, etc. play a role.
RainmanP
12-04-02, 07:34 AM
Well, ain't that somethin'! I plugged in my 81.5 cm inseam and got 169.5-6 down the board. Guess that confirms the good ol' 170 mm cranks on two of my bikes. I have 175 on a third bike. To tell the truth I can't feel much difference. Of course, I am only riding 25-30 miles a day on a regular basis, though I have ridden 50+ many times with both.
MichaelW
12-05-02, 03:57 AM
Cranks should be chosen primarily for biomechanical efficiency, ie related to the size of your leg. Mainly that means the size of your femur. The aim should be to keep the joints working through the optimum range of angles.
A second aspect is that they form part of the gearing system. For the same cog ratios, a longer crank gives lower gearing. Turning a long crank is more work than turning a short crank, since you are applying power over a longer distance. Longer cranks do not generate power, only you do, and gearing ratios should be set by the cogs, so its best to ignore this and concentrate on well fitting cranks.
Assuming you can work out a "normal" crank size for your legs, then there are reasons for chosing longer or shorter ones, depending how fast you like to spin your legs, how much cornering clearance you need.
To my mind, crank length is the very first variable you fix when designing a bike. You can then work out the bottom bracket height, seat angle, toe-clip overlap(avoidance) etc.
A second aspect is that they form part of the gearing system. For the same cog ratios, a longer crank gives lower gearing. Turning a long crank is more work than turning a short crank, since you are applying power over a longer distance. Longer cranks do not generate power, only you do, and gearing ratios should be set by the cogs, so its best to ignore this and concentrate on well fitting cranks.
Assuming you can work out a "normal" crank size for your legs, then there are reasons for chosing longer or shorter ones, depending how fast you like to spin your legs, how much cornering clearance you need.
To my mind, crank length is the very first variable you fix when designing a bike. You can then work out the bottom bracket height, seat angle, toe-clip overlap(avoidance) etc.
1oldRoadie
12-11-02, 10:36 AM
My wife, a 50+ cutie, rides a 48cm Bianchi road bike with 175 cranks. If I swap the cranks to a smaller size (even without her knowledge) she starts complaining that the bike "does ride right".
I guess that crank length is truly what feels good to you.
I guess that crank length is truly what feels good to you.
palooka
12-11-02, 02:59 PM
Originally posted by MichaelW
Turning a long crank is more work than turning a short crank, since you are applying power over a longer distance.
From my understanding, that's not true. Longer cranks provide more leverage, so given equal gearing you are actually pushing harder the shorter the cranks are.
Turning a long crank is more work than turning a short crank, since you are applying power over a longer distance.
From my understanding, that's not true. Longer cranks provide more leverage, so given equal gearing you are actually pushing harder the shorter the cranks are.
MichaelW
12-12-02, 05:54 AM
Originally posted by palooka
From my understanding, that's not true. Longer cranks provide more leverage, so given equal gearing you are actually pushing harder the shorter the cranks are.
Im thinking of it from the riders point of view. When cycling along, you use a gear which lets you apply a certain amount of force to the pedals. If the force gets to hard or easy, you change cogs. For a rider with long cranks, that force is applied over a longer circumference, ie more work per rotation.
You cant go comparing different cranks with the same cog combinations, real riders dont use them like that.
From my understanding, that's not true. Longer cranks provide more leverage, so given equal gearing you are actually pushing harder the shorter the cranks are.
Im thinking of it from the riders point of view. When cycling along, you use a gear which lets you apply a certain amount of force to the pedals. If the force gets to hard or easy, you change cogs. For a rider with long cranks, that force is applied over a longer circumference, ie more work per rotation.
You cant go comparing different cranks with the same cog combinations, real riders dont use them like that.