Cranck length decision

[GROB]

Can anayone advise on the benifits / decision on which cranck length to use - 175, 177 or 180?  when do you go for a longer crank arm - I belief taller riders can obtain more leverage (power) by using a longer crank length.

[xak1]

Look at this link - it is maybe extreme, but I do think as a result of "standard" crank lengths being stocked by LBS's, we do end up with shorter cranks.  I have gone for a 180mm crank and really see an improvement in climbing.

 

http://www.nettally.com/palmk/crankset.html

[GROB]

Thanks Xak, this is exactly what I was looking for!

[Mudsimus]

If longer cranks offer such a great improvement, why do most of the euro pro's ride with 172.5 and 175 cranks? I know for fact that Nolan also ride with 172.5 cranks and he is quite a tall rider. I rode 175 for years and then switched to 172.5. Will never change back. I'm 1.86m

[fandacious]

Look at this link - it is maybe extreme' date=' but I do think as a result of "standard" crank lengths being stocked by LBS's, we do end up with shorter cranks.  I have gone for a 180mm crank and really see an improvement in climbing.

 

http://www.nettally.com/palmk/crankset.html

[/quote']

 

Where the hell did you get a 180mm from?? I WANT!!

[Wonder Woman]

Look at this link - it is maybe extreme' date=' but I do think as a result of "standard" crank lengths being stocked by LBS's, we do end up with shorter cranks.  I have gone for a 180mm crank and really see an improvement in climbing.

 

http://www.nettally.com/palmk/crankset.html

[/quote']

 

Where the hell did you get a 180mm from?? I WANT!!

 

Hehehe...and here some of us are going for 170mm...you tall buggers!!!

[xak1]

I think again it depends on riding style and type of riding.  Shorter cranks for riding flats, sprinting, track - generally very high cadences.  As soon as climbing comes into the picture, longer cranks are used.  That is also why MTB cranks are normally longer than road cranks.  Also, body length is probably not a good way to determine crank length, as some people have longer legs compared to upper body.  As an example

 

A lot of pro's will actually change to longer cranks when they hit the mountains.  The following list is quite interesting - look at Pantani using 170mm cranks, but changing to 180mm cranks in the mountains.

 

Jacques Anquetil 175mm
Lance Armstrong 175mm
Chris Boardman 170mm
Santiago Botero 172.5mm
Angel Casero 175mm
Mario Cipollini 172.5mm
Fausto Coppi 171mm
Malcolm Elliott 172.5mm
Tyler Hamilton 172.5mm
Bernard Hinault 172.5mm
Miguel Indurian 180mm (190mm for second Hour record!)
Laurent Jalabert 172.5mm
Greg Lemond 175mm
Brad McGee 175mm
Robbie McEwen 175mm
Eddy Merckx 175mm
David Millar 175mm (180mm in TT)
Francesco Moser 175mm
Marty Northstein 167.5mm in Keirin (170mm in kilo)
Graham Obree 175mm
Marco Pantani 170mm (180mm in mountains)
David Rebellin 172.5mm
Roger Riviere 175mm
Jean Robic 170mm
Tony Rominger 172.5mm (175mm for Hour record)
Oscar Sevilla 175mm
Jan Ullrich 177.5mm
Rik Verbrugghe 175mm
Erik Zabel 172.5mm
Alex Zulle 175mm (180mm in mountains)

[PPWTF]

there was a post by BikeMaxPower with an attachment from some US sport science type place - real scientific research - basically theres about a 1% performance and economy difference between the different lenghts of crank offered.......

Vital for Pros, but for us mortals not really an issue, except for in the 'feel' and 'comfort' stakes, unless you have issues with old injury etc...

PPWTF2008-04-18 01:20:10

[xak1]

Unfortunately 180mm's are difficult to come by, but Dura-Ace and XTR make standard 180mm lengths, although difficult to get in SA.  Try Chain Reaction.  If you want to go longer, there are custom cranks, but extremely expensive.  Look at www.zinncycles.com .

[madmarc]

Increasing your crank length from 172.5 or 175 to 180 is not going to improve climbing by much.

 

Yes a longer crank will increase the torque and hence the power to the rear wheel but by very little

 

Example

 

from 172.5mm crank to a 175mm crank will increase torque by approx. 1.45%

 

from 175mm crank to 180mm crank will increase torque by approx. 2.86%

 

This torque is measured at the BB so with efficiency loses throught the drive train it will be even less at the rear axle and reduce even further by the time it gets to the outer rim of the wheel where contact is made on the road.

 

Crank length can be calculated in 2 ways

 

1- Rider specific - and take into consideration the following body dims

 

Thigh length

Lower leg length

Foot to Heel Length

High of foot above pedal axle

Ankle angle

 

2- Bike Frame dims

 

Which considers frame dims based on the bike being sized correctly for the rider.

 

Crank length calculations never take the riders power into consideration. and in my opinion it would be far easier and cheaper to increase power to weight ratio by losing 1 or 2 kilos

 

 

[Mudsimus]

I think again it depends on riding style and type of riding.  Shorter cranks for riding flats' date=' sprinting, track - generally very high cadences.  As soon as climbing comes into the picture, longer cranks are used.  That is also why MTB cranks are normally longer than road cranks.  Also, body length is probably not a good way to determine crank length, as some people have longer legs compared to upper body.  As an example

 

A lot of pro's will actually change to longer cranks when they hit the mountains.  The following list is quite interesting - look at Pantani using 170mm cranks, but changing to 180mm cranks in the mountains.

 

Jacques Anquetil 175mm
Lance Armstrong 175mm
Chris Boardman 170mm
Santiago Botero 172.5mm
Angel Casero 175mm
Mario Cipollini 172.5mm
Fausto Coppi 171mm
Malcolm Elliott 172.5mm
Tyler Hamilton 172.5mm
Bernard Hinault 172.5mm
Miguel Indurian 180mm (190mm for second Hour record!)
Laurent Jalabert 172.5mm
Greg Lemond 175mm
Brad McGee 175mm
Robbie McEwen 175mm
Eddy Merckx 175mm
David Millar 175mm (180mm in TT)
Francesco Moser 175mm
Marty Northstein 167.5mm in Keirin (170mm in kilo)
Graham Obree 175mm
Marco Pantani 170mm (180mm in mountains)
David Rebellin 172.5mm
Roger Riviere 175mm
Jean Robic 170mm
Tony Rominger 172.5mm (175mm for Hour record)
Oscar Sevilla 175mm
Jan Ullrich 177.5mm
Rik Verbrugghe 175mm
Erik Zabel 172.5mm
Alex Zulle 175mm (180mm in mountains)

[/quote']

 

Take note....Mountains. We dont have mountains in Africa.

[Canaris]

An interesting idea is as follows:

 

the knee if bent more than 90% loses its ability to push power out.

 

therefore crank length should b calculated in relation to the part of the leg that if moved changes the position of the foot, and also the angles of all the levers involved.

 

THis is the upper leg bone.  So take the measurement from knee to groin area and divide by two.  THis will give a ball park figure.  Fine tune for comfort

[White51]

For road racing you should use 172.5 or 175 and the 177.5 is and exception for very tall cyclists and 180s are for time trialling!

[Wonder Woman]

All I know is I went from a 172.5mm to a 170mm and was just so much more comfortable...who says it doesn't make a difference???

[White51]

It definatly makes a difference, no doubt!

[Christie]

I also saw the scientific study on crank lengths. Interesting findings! They varied crank length from 145mm to 220mm for the same rider, and found very little performance difference, because as the lenth increased, cadence came down accordingly.

 

I think choosing a length its down to personal preference.