What the F diffrence !!!

[HeartCoppi]

  the difference in  crank lengths will do nothing except change the fit of your bike. Putting a longer crank on will automatically mean you would have to raise the height of your seat so that you get proper leg extension during the pedal stroke.

 

I think thats its just the opposite. Remember longer cranks will lower the pedal. You might have to lower your saddle. But only really if you make larger changes like 170 to 175mm. You may not feel a 2,5 mm change as much as the 5mm in the example I've made.

 

 

 

I cant help but coming back to a senario of a tall guy and a short guy walking up the stairs. To one of them, taking one step at a time seems more comfortable than the other. The tall guy may feel more comfortable taking two steps with each stride. The tall guy uses more energy taking one step at a time. (short stride with long levers) The short guy uses more energy taking two steps at a time.(long cadence with short levers)

 

 

 

 

[Johan Bornman]

Interesting..so will there be a difference in fatigue levels?

Fatique level is a fluffy concept with no hard definitions or boundaries.

 

However, fatigue is related to how much work done.

 

Both identical individuals doing exactly the same course and distance but the one with a long and the other a short crank, would have done the same amount of work.

 

Work is simply a measurement of mass times distance.

 

Therefore both would have expended equal amounts of energy to cover the distance.

 

This is a frequently-debated topic here that occurs in two varieties: crank length and Q-Rotors (or BioPace or Ovali, depending on the era from which you hail).

 

An eloquent answer was once posted by a guy called Bruce, who roamed here before your day and now seems to have disappeared. Search for his post using his name as author and "linkages" and a keyword.

 

The simple answer is that from a physics point of view, we are absolutely certain about the amount of work performed. But no-one is quite certain if there is a biokinetic advantage in small crank length differences.

 

One of the posters above (sorry, in this view I can't see you else I would have acknowledged you) mentions individuals running up stairs. I use a similar analogy.

 

Crank lengh is like stair size. Most humans find stairs of standard height comfortable to climb. Either singly or in two's depending on haste.

 

Even very tall individuals still run up those stairs two-two at a time.

 

It appears that femur length varies very little compared to the wide variences in the human height and that this average is what determined today's building standards vis a vie stairs.

 

Same for cranks. The average is 172.5 and the few variants above or below it are small variants that don't seem to matter.

 

I believe that the best crank length for you is the one that the bike came with. It almost certainly won't be ridiculously long or overtly short.

 

 

 

 

[Jaco Steyn]

Johan, Will you please read my post regarding the crank length and tell me if I am completely of my rocker? Post over here : https://www.bikehub.co.za/forum_posts.asp?TID=60135&KW=&PID=899298#899298

[EigerSA]

 

  the difference in  crank lengths will do nothing except change the fit of your bike. Putting a longer crank on will automatically mean you would have to raise the height of your seat so that you get proper leg extension during the pedal stroke.

 

 

I think thats its just the opposite. Remember longer cranks will lower the pedal. You might have to lower your saddle. But only really if you make larger changes like 170 to 175mm. You may not feel a 2' date='5 mm change as much as the 5mm in the example I've made.

 

 

 

I cant help but coming back to a senario of a tall guy and a short guy walking up the stairs. To one of them, taking one step at a time seems more comfortable than the other. The tall guy may feel more comfortable taking two steps with each stride. The tall guy uses more energy taking one step at a time. (short stride with long levers) The short guy uses more energy taking two steps at a time.(long cadence with short levers)

 

 

 

 

[/quote']

 

  Oops... my bad, got confused there for a second... you're right, the seat would have to be lowered!

 

I

get what you saying about levers, but that's not the way people cycle,

the position of the foot in relation to where the power goes doesn't

stay constant at all, it varies depending on terrain or speed, as well

as high tired or fresh your legs are ect ect... by dropping your heels

slightly while pedaling will do more to change your cadence and power

than changing crank length.

 

Also if you want to change your

cadence, change gears or pedal faster, you want more power, change gear

or pedal harder... having a different length crank is not gonna

influence cadence or power.

 

Consider also where the existing

length has come from. As far as I'm aware, the crank length came

because it was the most comfortable length, not because it offered some

sought of improvement to cadence ect...

 

 

 

EigerSA2009-09-12 10:08:38

[JA-Q001]

My main reason for having different crank lengths comes to the type of riding I'm doing. For road races, where i want a good balance between exhilaration and powering, I use my stranded 172.5 cranks. When time trialing, where I mainly sit and power, I use a 175. This is also a good compromise for me, because I keep the Torque ratio between the crank arm length and the blade radius nearly the same (This is because I ride a 53 blade in a RR and a 55 in a TT). Another thing that evens out is my leg speed, because I push a heavier gear in a time trial, my cadence is lower than in a RR and because of the longer crank, I have to do a bigger circumference so my leg speed in meters/second stays the same as with the higher cadence and shorter cranks in a RR.

 

I hope this makes sense.

 

[Sterad]

It basically boils down to personal preference, and personal make up, wether you prefer a higher cadence or lower. You will have more churning power to push harder gears with a longer crank, but your cadence will be slower. Obviously if you are 1.6M tall go for the 170mm, if 1.8M go for the 175, to suite your height. I once tried 190mm cranks, had major power up hills, could basically drop down 1 or 2 gears from the 175mm cranks, but on fast down hills you spin out quicker, ie if you previously spun out at around 70km/h, you would now spin out at around 64km/h with 190mm cranks. But for hills and climbs it definitely helps.

[Aquatic]

 

 

 

It basically boils down to personal preference' date=' and personal make up, wether you prefer a higher cadence or lower. You will have more churning power to push harder gears with a longer crank, but your cadence will be slower. Obviously if you are 1.6M tall go for the 170mm, if 1.8M go for the 175, to suite your height. I once tried 190mm cranks, had major power up hills, could basically drop down 1 or 2 gears from the 175mm cranks, but on fast down hills you spin out quicker, ie if you previously spun out at around 70km/h, you would now spin out at around 64km/h with 190mm cranks. But for hills and climbs it definitely helps.[/quote']

 

 

Wouldnt the size of your chainring have an effect on cadence rather than the size of your crank?

[1hill@aTime]

wolfy you have opened pandora's box

[Sterad]

Yes but its a different thing. With longer crank arms you are able to push a harder gear, but your cadence will be slightly lower, because your foot now has to move through a longer circumference distance, but less force is required. So it has the effect of being easier to peddle, if you are a tall rider. Thats why it depends on the individual. Basically you have to find a crank arm length that best suites your individual ideal cadence speed.

Crank arm length will dictate your cadence.

 

Taller riders will find longer crank arms better, ie. if you are 1,9M you should be using 190mm crank arms because you will naturally have a lower cadence(in general)

[HeartCoppi]

I am 1,97 this is my pref:

 

 

 

[javadude]

Nice find Tarboy. Those are rare.  I read an interview with ex pro Magnus Backstedt who is 1.93m and he preferred 180mm cranks. He reckons the taller you are the longer your cranks.

[HeartCoppi]

The change from 172,5 to 175 made a big diff to me.

 

I rode 172,5 in the beginning because I was clueless.

 

Thats a 5mm change in total, my experience was awesome especially on the climbs. Might be room for the argument that its all between the ears.

 

The 180's made a huge difference, which dealt a blow to that argument. I experienced a huge diff on this additional 10mm in total.

 

Velo the diff = 200

 

Just have to remember to have the cranks horizontal when going over any small speed bumps.

 

 

[shimano 105]

When u put a small tyre on a car(outside diametre)it will rotate quicker with lower top speed.When you put a bigger tyre on the same car,it wil rotate slower,but with a higher topspeed.So,more torque,shorter,and less torque,longer.(bigger diametre)

[shimano 105]

To climbed better uphill,shorter,topspeed,longer.Short legs,shorter,longer legs,longer cranks.

[Dragu]

Also for peoples legs who is not the same length. A friend of mine was in an accident and as a result his one leg is slightly shorter than the other. Different crank lenghts help solve this problem...

 

My 5 cents..