Short Cranks vs Big Cranks, Which is Better?

[A.Z.KOETSIER]

This has been debated many times with various outcomes with pros and cons for both lengths.

Well I would like to know your own hands on (feet on) experiences with this matter and then maybe some extra info, here are mine

I have rode cranks from 165mm all the way to custom 1.25kg 200mm monster cranks.


INDOOR
On rollers I managed to get my highest speed with 172.5mm (didn't have shorter cranks at the time) reaching 103km/h. on the same day I only managed 92km/h on 200mm cranks. The limiting factor for both runs was the maximum cadence I could reach. Maybe If i had a big enough gear I would of been able to reach higher speeds on the 200mm as I would of had the leverage to turn it? (see gain ratio http://www.sheldonbrown.com/gain.html )

POLKA DOT
Climbing was my biggest surprise, and also the reason I initially got 200mm cranks using the inseam X 0.216 formula.

I didn't just beat my PR's I absolutely destroyed them. I could stay in a bigger gear for longer. In fact I hardly ever used my small ring.

Is this why Marco Pantani used 180mm cranks when climbing? (The 3 fastest times up Alpe d'Heuz ever) The last person to win the Tour and Giro in the same year.

1. 1995: 36:40 Marco Pantani 22.58 km/h
2. 1997: 36:53 Marco Pantani 22.45 km/h
3. 1994: 37:15 Marco Pantani 22.23 km/h
4. 2004: 37:36 Lance Armstrong 22.02 km/h

CRITERIUMS
In criteriums I hit the 200s so many times that I just stopped pedalling in most bends this made me loose ground and staying at high speed is everything in crits. When i switched back to 172.5mm my cadence did increase and I had to stand on some small inclines to keep the gear turning where previously I could remain seated. never the less I achieved my best results on smaller cranks and possibly also my fastest sprints.

TT
The Race of Truth would seem to be the best place to see which crank to decide on. but this wasn't the case i rode 165 - 200mm with little difference in performance. my main reason for trying out 165s is due to being able to raise my seat an extra 27.5mm and having my knee come up a massive 55mm less, allowing me to get lower on the TT bars, breath better with better aero . a win win win.

I found the 165s really comfortable to ride the diametre path of my foot was so small it felt like I was climbing up a little staircase. But turning a big gear was harder and to make up I had to increase my rpm. And any sort of incline meant the end of days. Since there was no real benefit in my speed with 165 even with all its aero advantages, I returned to bigger cranks to help on undulating terrain.

one thing thats also interesting to note is that my rpm might have dropped a lot on bigger cranks but because i was pedalling in much bigger circles my foot speed didn't really change, and foot speed X foot force = Power .....right?


SUMMARY (for me)

165mm might have been to small for climbs, 200mm might have been to big for crits and high speed sprints,
so maybe i'll look into getting a 180-190mm, which just happens to be the cranks Pantani used to become the greatest climber who ever lived and Indurain used to dominate the sport.

Ride the biggest crank you can spin....?

 

[Citius]

As you rightly point out - this has been discussed many times. There's no evidence to show that crank length makes any real world difference to real world performance. It's more a function of bike fit and leg length - and not much else. Ironically, what science there is seems to go against your own conclusions that 'longer must be better'.

 

[A.Z.KOETSIER]

As you rightly point out - this has been discussed many times. There's no evidence to show that crank length makes any real world difference to real world performance. It's more a function of bike fit and leg length - and not much else. Ironically, what science there is seems to go against your own conclusions that 'longer must be better'.

What works best for you?

 

[Citius]

I don't know what works best for me, because I have never ridden anything other than 170 on the road, 170/175 off road and 165 on the track. But they all work fine in isolation.

 

[MichaelW2]

165,170 and 175 are all within the medium size of crank length. For any rider within spitting distance of average size, it makes little difference which one of the medium cranks they select.
Proportional crank length can enable a more proportionate bike design as a whole, for riders further from average size:
For short riders: lowering the bottom bracket, reducing the length of a bike, reducing toe clip overlap.
For tall riders, you need to raise the BB to prevent grounding the pedals, and lengthen the rear triangle to avoid heel clips, which also replicates the front/rear weight balance found on medium bikes.

 

[A.Z.KOETSIER]

I don't know what works best for me, because I have never ridden anything other than 170 on the road, 170/175 off road and 165 on the track. But they all work fine in isolation.

It seems your crank choice actually follows the same reasons as mine

165 for track - high rpm and sprinting
170 - all round
175 for your off road - more climbing

 

[Citius]

It seems your crank choice actually follows the same reasons as mine

165 for track - high rpm and sprinting
170 - all round
175 for your off road - more climbing

You're assuming I made conscious choices - I didn't. High RPM and sprinting are only two considerations on the track for instance. There are many more than just those two. The majority of track work is endurance based anyway, so very little in the way of 'high rpm and sprinting' going on. Most tracks dictate 165 due to the banking, not because shorter is better.

 

[A.Z.KOETSIER]

You're assuming I made conscious choices - I didn't. High RPM and sprinting are only two considerations on the track for instance. There are many more than just those two. The majority of track work is endurance based anyway, so very little in the way of 'high rpm and sprinting' going on. Most tracks dictate 165 due to the banking, not because shorter is better.

Im not assuming anything, just responding to the info you gave me, and find it interesting that we are both riding proportionally smaller and larger cranks for similar situations.

Conscious or not

 

[Dogtrousers]

It all means nothing to me. However, this might be an interesting read.

http://www.sheldonbrown.com/gain.html

It's not 100% on topic, but the relevance is that the proposed system takes into account crank length in calculating the effective gear ratio of the drive chain. It might give you something to discuss ...

... or maybe not.

 

[Citius]

Im not assuming anything, just responding to the info you gave me, and find it interesting that we are both riding proportionally smaller and larger cranks for similar situations.

Conscious or not

Maybe I'm not being clear. I ride 165 on the track because the track says so. I ride 170 on the road because every road bike I have had has always come with 170 cranks. Likewise, I used to ride 175 off road, and only changed to 170 to have a bit more component commonality with my lad, who also rides 170 off road. There's very little - if any - conscious decision making going on there.

Ironically, when I changed from 175 to 170 off road, I noticed no difference whatsoever.

 

[A.Z.KOETSIER]

Maybe I'm not being clear. I ride 165 on the track because the track says so. I ride 170 on the road because every road bike I have had has always come with 170 cranks. Likewise, I used to ride 175 off road, and only changed to 170 to have a bit more component commonality with my lad, who also rides 170 off road. There's very little - if any - conscious decision making going on there.

Ironically, when I changed from 175 to 170 off road, I noticed no difference whatsoever.

Okay I see, so it was no more than coincidence. Maybe you are a Macro-absorber or maybe 5mm is to small to notice a difference, Or maybe I'm just hoping to find an answer thats not there

I guess crank length selection will remain a mysterious dark art that probably has no effect on most people.

 

[Sharky]

Have posted before - I switched to 150mm on three of my bikes and 145mm on another. Riding position much more comfortable with the higher saddle and surprisingly climbing feels better as you can stay seated for longer. In terms of TT performances, it is impossible to quantify, as each year I get older and it gets harder, but year on year, times are comparable, so satisfied with the benefits for me.

 

[Deleted member 1258]

My fixed and one of my geared bikes have 170mm cranks, my other geared bike has 172.5mm cranks, thats just because thats what they came with. On the fixed I prefer 165mm cranks, seems to make spinning easier, on a geared bike I have no preference.

 

[A.Z.KOETSIER]

Have posted before - I switched to 150mm on three of my bikes and 145mm on another. Riding position much more comfortable with the higher saddle and surprisingly climbing feels better as you can stay seated for longer. In terms of TT performances, it is impossible to quantify, as each year I get older and it gets harder, but year on year, times are comparable, so satisfied with the benefits for me.

Wow thats short! do you ride with a very high cadence or have a short inseam?

 

[Sharky]

Wow thats short! do you ride with a very high cadence or have a short inseam?

Cadence is higher, but in a lower gear. Don't have a cadence sensor, but circumference speed is the same, so doesn't feel any different from longer cranks. My height is 5' 9" with normal legs.

Lots of articles on the web, search for short cranks and also gain ratios.
Cheers Keith