0-20 in 5 Sec

Left/right? The same?

56/12 and 22/28

Whichever side has the teeth.

0-20 in 5 Sec

What's the physics behind it?

roadfix

The shorter the BB spindle, the less numbers you need to crunch....

56/12 and 22/28

Well, the side that has the teeth can grab the chain, so when you exert force on the crank, it drives the bike forward.

The side that doesn't have the teeth can't do anything with the chain, so it's not quite as efficient.

Mothra

Uh... while the right side may not have any torsional loads through the axle, I doubt there's much of a difference in efficiency and power-transmission. Certainly not enough to be noticeable. Can anyone give me a number, like 1.0 or 2.0% power-loss from the left crank compared to 0.5-1.0% loss on the right?

Dusk

Wow this is just too odd. What is it you want to know? A crank is a crank, but you may be a crank too. It is a Crank...it is what it is.

Now if you want to know which leg is stonger..... don't ask us......it is up to you to know your legs.

Really this has to be a joke post.

Jacobi

Wow, no need to be a dick! I'm sure that it was a legit question and, however minute, I'm sure there is a difference in efficiency between cranks.

E very
D ay
I
N eed
A ttention

Haha, I grew up in west bloomington.

-Barry-

Dusk

Dear Dick....or do you go by Barry now? Read the org. post he asks what "SIDE" of a crank..... not efficiency between cranks.... I agree diff cranks are diff. But that is not his question.

HAHA did we kick you out of the state for not reading things....LOL....

DrPete 

I think there would be a slight difference in the efficiency of the left crank arm vs. the right, mainly because the left would lose more to the torsional forces placed on the spindle. BB spindles are pretty solid, though, so unless you're a total gorilla I don't think the difference would ever be a significant, or even measurable, one.

DrPete

Jacobi

I apologize for my type, but I too meant a slight differene between SIDES.

Dusk

Hey no offense meant or taken. You cool?

When I put people on a Computrainer and can watch the power put out by each leg on the diff crank arms. The Crank itself is not an issue it is leg development and cycling style that effects power to the bike the most.

I still wonder what the org poster wants to know.

Jacobi

I think he wants to know, if each leg is equally strong, is there a difference in effieciency between the left and right crank?

Dusk

With todays cranks it is not an issue. The cranks are so good the diff in your socks and shoe insoles will have more effect than the crank arms.

Your legs more of an issue.

mcoine

The same arguement can be made for the rear hub, which has been a serious consideration of hub and wheel builders for a long time.

0-20 in 5 Sec

I thought it was a legitimate question. Maybe you don't -- nonetheless, you're obviously not happy I asked about it.

urbanknight

I would imagine the difference is far less than the difference between each leg. I know my right leg is dominant, and most racers know this because that's the leg they put forward when starting a standing start time trial. Still an interesting question, though, and I would imagine that the right would be more efficient because it is directly pulling on the chain while the left side has a drivetrain loss from having to turn the spindle which then turns the chainwheel.

AlanS

The left crank, right crank, chain ring are a single rigid body. How could there possibly be a difference in efficiency?

I nominiate this thread for the BF Top Ten most idiodic threads of 2006.

Jacobi

Would you say that a tranny, driveshaft, and rear diff are a single rigid body? If so, which I'm guessing you would...how much flex do you think there is in this combo? I'm guessing that one side will flex more than the other, however minute, but I'm guessing there might be a small difference.

P.S. This is a message forum. If people feel like asking questions that you feel are idioTic, then feel free to post elsewhere. No need to be a dick when someone asked an honest question. If you are so intelligent in the ways of the bicycle, could you tell me who has published your book, "I'm god of bicycles, let me teach you something!"

urbanknight

Well put Jacobi. I have a front wheel drive car with a sideways mounted engine. This is the most efficient setup possible, yet it still gets a 20% drivetrain loss (120 hp at the crank, under 100 at the wheels), which is why I find it entirely possible flex and movement between the crank, the spindle, and the rings can occur. While this seems to be a useless topic to me (work on the leg equality first) it is in fact very intriguing, and I wouldn't mind hearing some physics experts state their opinions.

iansir

No such thing as a rigid body on a bike 'flexing' does not dissipate energy. Inelastic (plastic, permanent) deformations dissipate energy. If the material remains elastic (like almost any bike component, if designed properly), no energy is dissipated. If flexing occurs, there may be a difference in how much power you can put to the drivetrain or your comfort factor, but physically, no energy is dissipated.

Jacobi

Okay, now we're getting down to the absolute nitty gritty, but here goes. Flexing produces heat, this is evident when you bend metal over and over until it breaks (flex it) and touch it after it breaks, it will be warm. The heat is lost energy. So, given this to be true, if one side of the crank flexes more than the other, there would be more energy lost to heat.

P.S. I love debating these sort of things, I just hate it when some f'ing know-it-all comes along and forgets the true purpose of these forums.

botto 

too late. the 'Who Got Buzzed?' thread is by far the most idiotic, not to mention irrelevant, thread of the year by a long shot.

Mothra

There's a BIG differences between flexing something to a point well below its yield-strength and having it flex back into its original position, versus flexing something beyond its yield-strength & ultimate strength so that it actually breaks.

Retro Grouch 

I'm convinced there's a difference but I don't fully understand why. Here's what I know for sure: It's not uncommon for people to post of their left crankarm falling off of the bottom bracket spindle. I don't think that I've ever heard of someone having the same complaint regarding the right crankarm.