It's a commonly held belief that the taller the rider
the longer their crank should be.
For example, a rider of around six foot should have cranks
of 175 millimeters, and a shorter rider under five foot nine
should ride cranks of around 170 millimeters.
But does this belief hold any water in the modern
Pro Peloton.
Well we're here at the Abu Dhabi Tour to conduct
an in depth survey amongst the World Tour teams
to find the answer to that very question.
This is by no means an exact science,
but a very rough formula for crank based on height
is as follows.
This formula assumes that the crank length
is around 9.7% of our height and that everyone
is of roughly the same proportion
which, of course, we aren't.
It doesn't take into account
the length of the tibia, femur, and foot
which of course are key biomechanical factors.
Now another important thing to point out
is that cranks are only readily available
in 170, 170.5, and 175 millimetre lengths.
Riders under 175 centimetres in height
only have a 170 millimetre cranks and above as their option.
I race on 172.5, then laterally 175 millimeter cranks,
but the formula suggests the I should be
on the 177.5 cranks as I'm 183 centimeters tall.
That all said.
What does our sample of 100 World Tour riders
indicate to us.
It's this rough formula a useful guide or not?
Dimension Data pit now.
That's Igor Anton's bike.
He's a climber pretty small.
I reckon he should be on 170s.
Let's check.
Yep 170s fits with the formula.
30 of the sample group used 170 millimeter cranks,
and their heights ranged between 169 centimeters
and 181 centimeters.
43 of the group were on 172.5 millimeter cranks
with heights between 172 centimeters and 187 centimeters.
26 of the group rode 175 millimeter cranks
with a height range between 182 centimeters
and 190 centimeters.
From this, we can see that riders largely stick
within the formula.
Does this mean that the formula is right?
Well, no.
As you can see by the height ranges,
there are more than a few anomalies, and one rider,
our friend Adam Hanson was out on his own
riding 180 millimeter cranks and he's 186 centimeters tall.
Adam, we know you run pretty long cranks, 180 mils.
How did you come to that decision to ride cranks so long? -
It first started years ago. When you had an SRM
Used to have to work out the slope yourself
in those big formula for you.
Five kilo weight and it was all pretty complicated.
You had to put a crank length in there
that sort of surprised me.
I worked out from that
that power equals torque multiplied by RPM.
My theory was always based on okay, so the longer the crank
the less torque you must put on the pedal.
The less weight you put on the pedal for the same amount
of power.
For me it's a more efficient way of riding.
A good example is if you take a nut off a wheel
of a car, if you have a short leverage it's really hard.
But with your long one it's easy to change the tyre
and take the nut off the wheel.
It's a lot less effort that has to be put in for the same
amount of force.
I spoke to a few mechanical engineers.
I prefer to speak to them to a biomechanical engineer
because a biomechanical engineer knows more about the body,
but doesn't know the effect of what the body does
onto the bike.
The best for your body to produce at maximum power,
but that power transforming from the pedal
back to the back wheel, that's more mechanical
because it goes through crank arms, right?
A mechanical engineer will say it's far more efficient
to have a longer crank.
- That effects your, it's simple physics.
Isn't it?
It's leverage it's far more efficient,
but you're a pretty tall guy as well.
So I guess you're more predisposed to be able
to ride efficiently with longer crank as well.
- Well if you talk about rider height,
Pantani's 180 cranks.
He's short.
He's super short.
He used to climb like a goat.
If you compare the crank lengths to ratio of the leg,
I'm actually using super short ratios
like my crank arm lengths and my leg ratio
to Quintana.
I'm probably 40% longer legs than him,
but my cranks not 40% longer than his.
Maybe like five or 4% longer than his.
I truly believe it comes down to manufacturers.
Shimano, Campag, and Sram
I don't want to say bad things about them,
but I know bike shops they
cannot have 20 pairs of cranks.
They want to make a standard 172.5.
Everyone rides 172.5 here.
Okay, if you're huge you go to 175 or 180s.
So it's just easier for the bike manufacturer
to make one standard crank length everyone rides
and that's it.
- A short answer is a lot of thought
has gone into determining
your crank length without a shadow of a doubt.
Absolutely fascinating!
- For sure, I wouldn't just jump on anything.
- One of those anomalies from our group was Nairo Quintana.
He was the shortest at 167 centimeters tall,
but rode 172.5 millimeter cranks.
At the other end of the scale, track rider John Dibben
at 185 centimeters tall rides only 170 millimeter cranks.
We're here with Katusha.
They've got one particularly tall rider, Ilnur Zakarin
who according to the formula should be
on 175 millimeter cranks.
Let's go and check.
So here's Zakarin's Ultimate CF SLX, red cranks.
Let's have a little peak.
Ah, 172.5 interesting.
This is Julian Bernard's bike, and as you can see
it's a very, very small frame,
so you'd typically think this rider
being a small, light climber would 170 millimeter cranks.
Let's have a look.
And he actually bucked the trend a little bit 172.5.
The formula is a rough guide and only that.
There are number of other factors we haven't touched
particularly cadence and riding style,
and that's another video entirely.
We know this topic will ignite the comment section,
and we'd love to hear what you have to say.
Well, I think you'll agree
some very interesting results there.
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Now sticking on the subject of cranks,
how about clicking just up here for a GCN science video
when we look at importance or not of crank length,
and click just down here for the importance or not
of saddle height.