Triggered by the ‘standards’ thread.

At 5’6″ what should be my optimum crank length?

It’s leg length not height that you should look at.

Have a look here

I’m a similar height and like 165’s best but 170 are also fine. My knees didn’t like 175’s if it involved mainly sat down riding.
If I ride the 165’s for a long time then the 170’s I can tell no difference but in reverse I can.

I’m not sure there’s a definitive answer to this, though people will have opinions.

Personally I’m 5ft 8in with short legs and happily ride 165, 170 and 175mm on Mtb.

5’7″ and I definitely prefer 165s, though I’d like to try even shorter. I just find it easier to climb with them.

Asking as I’ve recently had a knee issue and wonder whether switching to shorter cranks might help avoid further problems?

It all depends on what you fancy, are used to and BB height. Unless your legs are at the extreme end of long/short.

Gee Atherton is 6 foot 4 and uses 165mm . Discuss… 🙂

BB height is relatively low. My Alpine is fond of the odd pedal strike, so going shorter could help there too.

And legs are relatively short – 29 inch inside leg…

6’2″ here, use 170 but I’d gladly go 165.

5’6″ and use a 165mm crank

I’ve just been looking at this whilst sizing up for my reverb.

Am I right in thinking,with my saddle at the right height, I should have a slight bend in the knee at full extension (crank turn)?

According to some, and there seem to be some pretty good arguments for it, 145 for an average person. Clearly the ~5% variation readily available is not reflective of the range of leg lengths in the human population. I am taller but plan on getting some 160/165 to try out….

5’9″ here with 32″ legs and 175 on most, but 165 on DH bike and 180 on Single speed, notice the 165s and the 180s but can’t tell between 170 and 175.

OP – I notice there’s a nice fella on the classifieds selling 165mm zee crankarms, in case you’re after a pair now.

Nobeerinthefridge. I’m 6ft3 and have always run 175s. Have thought about 180s. Out of interest, Why do you run 165 is it for cadence, rock clearance etc?

CRANK LENGTH – 2 Discussions

http://powercranks.com/cld.html

http://www.powercranks.com/assets/pdfs/Performance_Products_-_Exploring_Crank_Length.pdf

https://www.stevehoggbikefitting.com/bikefit/2011/06/crank-length-which-one/

http://velocitysportscycling.com/cycling-myth-busting-from-team-sky/

Crank length…

https://www.cervelo.com/en/engineering-field-notes/a-new-spin-on-crank-length

Some interesting links there. Thanks.

^ worth reading the link to Cervelo’s article on it.

But for each of these pros, the change to a shorter crank solved a range of motion issue at the hip that allowed them to comfortably make other changes to reduce aero drag without decreasing power.

That’s the key bit for me, it’s just part of a bike fit. I’ve changed to a shorter crank (165-170mm at 34.5″ IL, hardly short but as a tweak it seemed to help) on a long-distance bike to suit a different seated position, nothing to do with aero, all about comfort over long periods. Shorter allowed me to sit and pedal effectively in a comfier position. Before that I’d been able to get comfy but felt like I lost output somehow, ie comfier meant relaxed and less pedal impetus. Yet another bike with a really laid back position is fine on 175mm, it’s a SS MTB so I stand to ride or to pedal a lot more.
I’d say it’s related to bike position and use as well as a simple leg length relationship, maybe about whether you spin or mash also, and 5mm is not really a big difference anyway.

Pinnacle specced 170mm cranks on an MTB in the larger sizes a couple of years ago, got marked down in a test and we had a suprising amount of negtive feedback on it so we went back to 175. I thought most L size MTBs would be better on 170s, tbh it wasn’t a big change or a big deal either way imo, but there seems to be a perception that 175 is correct for any male of average height or above.

About your height and a spinner.

Tried 170’s about 10 years ago, they made a huge difference – pedalling became much more fluid, it just feels much more natural.

Have 170’s on all bikes now, going 165 on the new bike.

Proportional sizing makes so much sense, not just with crank length.

If we have to have three wheel sizes, let’s use them.

Some manufacturers adapt geometry and tubing to suit differently sized bikes, some don’t – you often get the same fork throughout the range too.

I’ve got a set of aerozine x1 cranks sat in a box. They have the pedal inserts that flip so you can run 170 or 175 (172.5 with a different insert)

After reading those articles I think I might do a bit of experimenting.

Thanks

Also worth experimenting with cleat position, that’s another +/-5mm in that area. I found a shorter crank also felt good with a more rearward cleat position, ie my foot stayed in the same place relative to the rest of me and the BB but I may use slightly different muscles or find a certain pedalling action more natural – tbh I don’t know why, it just felt better after a bit of to-fro and a lot of miles.

I’m 5’10” and switched to 170mm from 175 a few years ago. Around about the same time, my long standing knee issue started to clear up and hasn’t bothered me since.

The chap who suggested 170mm to me also suggested 165n to a 5’4″ friend of mine. However, this was all based on a dynamic analysis of pedalling rather than a call off list of height vs crank length.

For those whose knees don’t mind, it doesn’t matter. For those whose knees do, 2.5mm can make all the difference.

Im 5ft5″ and switched to 165 from 170 a few months ago..
I think they feel better but not sure how much of that is in my head.

I also slightly changed gear ratios and am spinning slightly faster in lower gears. Would definitely stick with 165 now..

I’m 6’2″, 36″ legs. Increasingly my 38yr old creaky knees are favouring the 165’s that come off my wife’s bikes…

Tried various lengths, felt no difference whatsoever.

Old bike 170mm, new bike 175mm I can’t tell the difference. If in doubt go short for more ground clearance.

I’m 5’10.5″ with relatively long limbs but a fairly messed up right ankle whose restricted movement puts extra strain on my knee (causing patellofemoral syndrome). Despite being out of the saddle (or with it dropped) a lot my seat height seems quite critical and I think crank length makes a difference too (though not having anything pulling on my knee caps – like pads – is even more critical). I think 170mm cranks are better for me than 175s (having recently gone back to the longer ones) and I’ve just ordered some 165s to see if that helps…

“I don’t think anybody’s really messed around with crank length yet because we’re constrained by history. I’d like to see a lot of people using 150mm cranks. All of the physiology data I’ve ever seen says that for an endurance athlete crank length actually doesn’t make any difference. But shorter cranks mean you’re more aerodynamic – if you’re trying to get into a tuck you can get lower because your knees aren’t coming up. So shorter cranks could produce a really big net gain but it’s a fashion thing.”

Chris Boardman’s seven tech trends for 2016

http://www.cyclist.co.uk/in-depth/360/is-there-a-correct-crank-length

http://www.bikefix.co.uk/right-crank-length

http://www.bhpc.org.uk/short-and-sweet-a-discussion-on-crank-length-by-mike-burrows.aspx