crank arm length??

[naffets]

i fancied upgrading my present compact to a carbon is there much difference between my old crank arm172.5 and the upgrade of 175????

 

[jimboalee]

What is the distance from the floor to the centre of your hip ball joint?

What is your 'natural' cadence?

 

[naffets]

i always thought the rule of thumb was short legs short cranks but would you notice the 2.5mm change in length??

 

[Will1985]

If you do change, don't forget to lower your saddle a tiny bit.

 

[hubgearfreak]

is there much difference between my old crank arm172.5 and the upgrade of 175????

1.4%. so no, not much

 

[andrew_s]

If you do change, don't forget to lower your saddle a tiny bit.

raise it a tiny bit

the pedal on a short crank is further off the ground at the bottom of the pedal stroke than the pedal on a long crank

 

[Will1985]

He's thinking of going from 172.5 to 175. That means without any change, the distance between saddle and pedal at the bottom of the revolution will be greater.

 

[jimboalee]

If he buys the correct length crank for his Hip Height, everything equals out because Saddle Height is a proportion of leg length.

Unless he has a weird Pelvis; and then he can 'Fine adjust' by riding some distance with a hex key in his pocket.

 

[02GF74]

2.5 mm difference so total change in stroke is 5 mm.

 

[jimboalee]

2.5 mm difference so total change in stroke is 5 mm.

What's the increase in pedal velocity?

 

[Globalti]

When I go from my 172.5mm road cranks to my 175mm MTB cranks I do notice a difference for about 3 seconds. Going the other way I don't notice.

 

[SimonR]

Hey there,

I've always found This to be a useful source for info about crank length. It's a compelling argument!

Incidentally, this bloke also has an interesting page about general issues regarding making a bike fit. It's here.

Hope that's helpful.

Simon R.

 

[jimboalee]

Hey there,

I've always found This to be a useful source for info about crank length. It's a compelling argument!

Incidentally, this bloke also has an interesting page about general issues regarding making a bike fit. It's here.

Hope that's helpful.

Simon R.

That method draws a relationship based on the pelvic girdle ( sit bones ) that are sat on the saddle.

The method I prefer is based on a relationship with the centre of the hip ball where the femur pivots.

 

[rickangus]

If you make a gap of 2.5mm between your finger and thumb you realise quite how small and insignificant a change this is.

Bike manufacturers like standardised fittings very much (obviously) and as a consequence crank lengths don't vary very much. By and large it is 165mm shortest to 175mm longest, a variation of less than 3% on standard 170mm cranks.

I would hazard a guess, based on frequenting this and other cycling forums, that adult rider heights vary between 5' and 6' 8" a variation of plus or minus 14% on an average of 5'10".

Clearly, if cranks were available as a proportional of leg length some much longer (and shorter) cranks would be warranted. When I tell people I use 200mm cranks they look at me as if I'm from the planet Zogg. They are only 1" longer than standard and offer me masses more comfort and efficiency. However, because they are outside of the industry standard many people are unable to comprehend that they can possibly work quoting all sorts of nonsense as to why they cannot or even should not be used.

There are lots of analogies than can be drawn which I won't otherwise I'll be here for ages and bore most readers rigid but I am a passionate believer in having cranks fitted as a specific percentage of leg length - as outlined in the articles linked to in SimonR's post above.

 

[jimboalee]

If you make a gap of 2.5mm between your finger and thumb you realise quite how small and insignificant a change this is.

Bike manufacturers like standardised fittings very much (obviously) and as a consequence crank lengths don't vary very much. By and large it is 165mm shortest to 175mm longest, a variation of less than 3% on standard 170mm cranks.

I would hazard a guess, based on frequenting this and other cycling forums, that adult rider heights vary between 5' and 6' 8" a variation of plus or minus 14% on an average of 5'10".

Clearly, if cranks were available as a proportional of leg length some much longer (and shorter) cranks would be warranted. When I tell people I use 200mm cranks they look at me as if I'm from the planet Zogg. They are only 1" longer than standard and offer me masses more comfort and efficiency. However, because they are outside of the industry standard many people are unable to comprehend that they can possibly work quoting all sorts of nonsense as to why they cannot or even should not be used.

There are lots of analogies than can be drawn which I won't otherwise I'll be here for ages and bore most readers rigid but I am a passionate believer in having cranks fitted as a specific percentage of leg length - as outlined in the articles linked to in SimonR's post above.

Are you 7'3" ?