Autobus

I've been using 170mm for years. Bulletproof sells cranks as short as 140mm I believe!

Would something like 160's make it easier to spin down hills at 110-120 rpm? I run a 48x18 fixed. The downside would be loss of power on the flats and inclines?

hockeyteeth

You should stay away from 160s unless you have short legs. Small canks turned by long legs is inefficient.

Why do you want to spin so fast on the downhills? Just get a lower gearing if you just want to spin faster.

pinkrobe

I used to run 180's and could spin those pretty good. Sorry, I'm not helping...

mander

I'd say you just need to get better at spinning.

oldsprinter

160mm sounds great. Quick acceleration, better cornering, better on your knees - and some tests have shown that short cranks are ergonomically more efficient on the flat. I'd try them (and if you do buy them please tell us what you think of them).

666pack

i run 170s and would never consider going shorter.

kludge

i run 132 cranks. i have a rare disability.


Duhmachfwolsydromitus

andre nickatina

i wouldn't go lower than 165. i like my 170's, hate my 175's except while going up hills.

LóFarkas

You bet I would. If I were 5 foot tall.

When will people realize at last that short cranks won't help chicken****??? Yeah, you can spin a bit better with a shorter crank... but you lose a bit of leverage. It's exactly like switching to a taller gear ratio, only you **** up your biomechanics as a bonus.

oldsprinter

People are too hung up on the "170mm is best length" idea. 170mm is specced by most bike firms because it's a good all-round length and suits most people over most terrain.

If you want to climb a mountain, go a bit longer - 175mm.

If you want to set an hour record, you might want to do what Sosenka did (https://www.sosenka.cz/ENG/extra07-06.html).

On the other hand, if you're looking for fast acceleration and short bursts of speed you might want to do what the 1989 world professional sprint champion Claudio Golinelli did and ride 155mm (not a typo) cranks! (There's a good vid of Golinelli here: https://www.youtube.com/watch?v=BkkTSVVrPYk ).

Golinelli is about 175cm tall, no giant I'll admit, but not 5 foot either.

I ride 165mm on the track and road - I would happily go shorter on the track and/or my fixed bike I ride to work on.

Autobus

Do you have a link to this study?

fatbat

If you can't spin down hills easily at 110-120 rpm with 170mm cranks, then some time spent working on bike fit and pedal stroke would probably help you much more than new cranks.

queerpunk

LoFarkas, usually you say good things, but this isn't one of them.

I am 5'5" tall, which has a lot to do with my story: i went from 170 to 165 on a new bike (also with criterium drops), and found comfort on a bike that i hadn't found before - especially in the drops.

short people have different proportions than tall people and it's foolish to think that stuff like 170 cranks and track drops are going to provide the same level of comfort. quite frankly, losing <3% of leverage (5/170) is a small price to pay for equipment that will maximize the smootheness and efficienency of my stroke.

MIN 

I have 155mm on a single speed MTB and that was motivated due to the 24" inch rear wheel (needed pedal clearance.) Down side is loss of climbing torque, plus side is smaller stroke circles at speed. Since I rarely speed with the bike (3" rear tires), it sucks. I would ride 175mm if I could on that bike. I'm 5"11" 32.25 in inseam - I ride 175 on my road bike.

estratton

I run 170 on my fixie and have found I'm very happy with it. I plan on getting 170 for my bfssfg iro as well as any other bikes i might pickup. whether to run it 49/16, or 48/16 or what is still in the air, as the fixie i have now is gear 50/15, which is great on long flats, but sucks to skid on, as well as for climbs.

yairi

Some good discussion at biketechreview on this ... https://biketechreview.com/phpBB2/viewtopic.php?t=1358

There's more there if you have a sniff around - one guy (the forum admin) went to a set of 140mm cranks on his TT bike and did very well with them (usually rides 175s I think). And then there was the guy on a tri forum (slowtwitch.com) that usually rode 180s, (tallish guy) and then switched to 200s and had great results with that.

I don't believe that this is something that has been completely figured out yet. Find what works for you. My thinking is - good aerobic engine and good coordination your strength? go for short cranks ... good muscle power and endurance more your thing? long cranks.


edit: oh and keep in mind that all those HPV records are usually set on very short cranks, 140, 150 is common.

Also you can keep the same gain ratio (see: Sheldon) by changing your gearing to suit your cranks. This way you can keep the same relation between the force you're applying to the pedal and the speed of the bike, while varying your foot speed.

Aeroplane

This is because their intended original use is on BMX bikes. A lot of kids ride BMX bikes. Kids are smaller than me. I like 165's just fine.

oldsprinter

I wish I could find it again. But bascially it found the 170mm is the worst length. Short cranks are great for speed on the flat, long cranks are great for climbing. Something around 150mm was shown to be far better than expected.

If hour records have been set on 190mm cranks, and world championships have been won on 155mm. 170mm cranks might not be the best for everyone.

fatbat

This seems a little backwards to me:
With short cranks, you have to apply more force to the pedals, and move your feet slower for a given RPM.

(from the biketech review thread
At 114rpm, 180.0 crank, 300W pedal speed is 1.074m/s and 31.4lbF
At 114rpm, 172.5 crank, 300W pedal speed is 1.03m/s and 32.7lbF
At 114rpm, 140.0 crank, 300W pedal speed is 0.84m/s and 40.3lbF

So short cranks should appeal to the strong but slow legged among us- more force and slower movement at a given rpm/power output.

Wheras the longer cranks should appeal to people with les strength, but good aerobic fitness and co-ordination, who want to move their feet further, faster, but with less force.

yairi

That's a good point, but I think you also have to consider that it will be possible to spin the shorter cranks faster, and in fact that your natural cadence will change depending on the crank length.

Autobus

Why?