Benefits to a larger crank arm?

[Captain Fastbastard Mayhem]

the longer the crank length the lower the seat hight.

the lower the seat hight the smaller the hip angle to your leg to at the top of the peddeling cycle.

 

these points are more important to remember. as a new bike fit might be in order.

Yes. 

 

Also, some people are more able to adapt to the more exaggerated hip and knee angles than others/ 

[cdevil]

I'm 1.90m tall and ride a 170mm crank, I honestly couldn't feel the difference coming from a 175mm crank, only difference is I now have fewer pedal strikes.

[Captain Fastbastard Mayhem]

I'm 1.90m tall and ride a 170mm crank, I honestly couldn't feel the difference coming from a 175mm crank, only difference is I now have fewer pedal strikes.

that's why I want to switch from my 175's to a set of 165's. I get loads of pedal strikes due to my very low BB and a bit of muppetry on the bike. 

 

Yes, I know that in order to maintain the same cadence (and therefore speed) I'll need to put out more net power (about 3%) due to the decreased torque that the shorter crank arm allows, but that just means more gainzzzz for me in the long run. 

[mecheng89]

The tallest member of our club, a hefty 6 ft 9 in changed from a 175 to 180mm and he says it feels more comfortable. THAT SAID, he hasn't raced with it yet, only training/coffee rides. 

 

Will provide feedback. 

[Karman de Lange]

For the same gear ratio, longer crank will give more power, BUT this will be only if you run out of gears. So if you changing to get more power, cheaper to simply change chain ring or cluster

 

Short cranks do help with higher cadence, but so does lowering your seat. (so no real reason for that either)

 

I have 165, 172.5 and 175 cranks on my  bikes .. (i'm 186cm) and  one can notice a  difference on the 165, but not really the others

 

So basicly

 

Go with the norm, and you can sell it again later for good price and not need to drop price for "special" items

Edited April 11, 2017 by Karman de Lange

[cdevil]

that's why I want to switch from my 175's to a set of 165's. I get loads of pedal strikes due to my very low BB and a bit of muppetry on the bike. 

 

Yes, I know that in order to maintain the same cadence (and therefore speed) I'll need to put out more net power (about 3%) due to the decreased torque that the shorter crank arm allows, but that just means more gainzzzz for me in the long run. 

 

We're both riding 2015 Giant Reigns if I'm correct so same geo and BB height except yours is a bit more raked out.

 

I experienced significantly less pedal strike going from 175's to 170's and honestly couldn't feel the 3% difference. The jump from 175's to 165's would likely be noticeable but if you're not very tall I rate you'll get used to it after the first ride.

 

Interesting article on the subject of crank length and pedaling efficiency: http://www.cobbcycling.com/crank-length-coming-full-circle/

Edited April 11, 2017 by Carel de Villiers

[Mr lee]

The tallest member of our club, a hefty 6 ft 9 in changed from a 175 to 180mm and he says it feels more comfortable. THAT SAID, he hasn't raced with it yet, only training/coffee rides. 

 

Will provide feedback. 

 

Ok great. It is the comfort I am looking for

[Captain Fastbastard Mayhem]

We're both riding 2015 Giant Reigns if I'm correct so same geo and BB height except yours is a bit more raked out.

 

I experienced significantly less pedal strike going from 175's to 170's and honestly couldn't feel the 3% difference. The jump from 175's to 165's would likely be noticeable but if you're not very tall I rate you'll get used to it after the first ride.

 

Interesting article on the subject of crank length and pedaling efficiency: http://www.cobbcycling.com/crank-length-coming-full-circle/

Sweet. Good to get real world feedback to back up the theory... 

 

And yeah. Reign. Not very tall at all either. 1.8 dead. 

[Captain Fastbastard Mayhem]

We're both riding 2015 Giant Reigns if I'm correct so same geo and BB height except yours is a bit more raked out.

 

I experienced significantly less pedal strike going from 175's to 170's and honestly couldn't feel the 3% difference. The jump from 175's to 165's would likely be noticeable but if you're not very tall I rate you'll get used to it after the first ride.

 

Interesting article on the subject of crank length and pedaling efficiency: http://www.cobbcycling.com/crank-length-coming-full-circle/

That is a very interesting article, thanks!

[Long Wheel Base]

Am riding 180 at the front of my race tandem. Even on a road bike pedal strikes is a problem, But we just had to learn to ride corners and bumps differently and it's no longer an issue. Initially our sprinting was not as strong. I also felt our climbing was not as strong. BUT with time I am getting used to the longer cranks. Don't think I will go shorter on the  tandem anytime soon. On my single bike I don't think I am strong enough to ride 180 cranks. The sprint is getting a lot faster and for the climbs I just need to rule number 5 and get stronger. Did also notice hip flexors took strain initially but worked them in the gym to sort that out. Dropped the saddle slightly and moved it forward a little bit(about 5mm down and forward). I am 184cm and ride a very aggressive setup. Drop from saddle nose to top of bars is 14cm. 

[openmind]

Many of you are confusing power with torque, they are not the same.

 

On the same bike under the same conditions the same person will need to put out exactly the same power (watts) to go a certain speed, regardless of whether the crank is 160mm or 180mm.

 

The longer crank will reduce the amount of torque (Nm) required, but will force the rider to pedal a larger circle and thus use their muscles differently to if the crank was shorter. 

 

Human physiology is complicated and the ideal crank length will depend on how you are made, i.e. at what length (torque) you are able to put out a given power most efficiently. That is not an exact science hence the need to experiment. 

[Shell Belle]

I have 170mm on my race bike and when I put a new groupset on my training bike, 172.5mm was fitted erroneously.  I am 1,65m and found that on very steep climbs I really struggled to turn the pedals.  I have had the crank arm changed back to 170mm and find climbing much easier.  It may all just be in my head, but it works for me 

[Captain Fastbastard Mayhem]

Many of you are confusing power with torque, they are not the same.

 

On the same bike under the same conditions the same person will need to put out exactly the same power (watts) to go a certain speed, regardless of whether the crank is 160mm or 180mm.

 

The longer crank will reduce the amount of torque (Nm) required, but will force the rider to pedal a larger circle and thus use their muscles differently to if the crank was shorter. 

 

Human physiology is complicated and the ideal crank length will depend on how you are made, i.e. at what length (torque) you are able to put out a given power most efficiently. That is not an exact science hence the need to experiment. 

Yes and no... Agreed power is the wrong word and for a given tooth count the overall power exerted (work) will remain the same.

 

If the lever arm is shorter, and the force at the pedal is the same, then the resultant torque will be lower because torque = F x radius.

 

You are able to exert a larger amount of torque on a longer lever by virtue of its length (same calc) but in order to have the same resultant torque on a short lever, you need to exert more force at the pedal. 

 

A longer crank will reduce the amount of FORCE required, as the lever arm is longer. 

Edited April 11, 2017 by Myles Mayhew

[CAAD4]

Analysis Paralysis. It's been said. Pedal strikes.

[The Guy in Pink]

I use 180mm on my road and 177.5mm on my Mountain bike, and my mountain bike frame has nice high BB clearance.  

It's an age thing, (next BD is no 70) with less strength available the longer torque arm is useful.

I'm still able to spin them quick as I was schooled correctly long ago (in the '60's)  with our early season club races being restricted to gears of 72" max (48/18 or 53/20).

[Johan_Kleynhans]

Interesting topic.

 

What about knee problems with changing cranks? I would assume not only do you have to lower or raise your saddle to accomodate a different length but also adjust it forward or backwards.

 

I used to train on one bike and race on another and I developed knee problems only to discover the saddle on my race bike was different to the training bike in terms of how far back I sat in relation to the 3 o clock/9 o clock losition. It was only 15 mm but my knees felt it. The cranks were the same length though.

 

Shorter cranks which results in having to put down more effort will also put more strain on knees.

 

Anyway just my thoughts on the matter.