Just debating giving 165mm cranks a go.

My knees aren’t the best, do suffer some real knee pain on longer rides where everything is getting tired. Set and reset saddle, up and down, fore and aft.

Currently using 175s, they are definitely too long for me. I had a bike with 170s, didn’t really feel to different in terms of torque, but spun up and remained spinning much more nicely, knee pain was reduced a little.

My inseam is 32″, will 165mm cranks be a big mistake rather than 170s? Been on lots of calculators and tables, anywhere between 165 and 170 has been recommended.

I run 1×10, generally grind out long climbs standing, worried that 165 will lack the torque. I am a BMXer though, so my standing leg power is pretty high.

Get the right size for your leg length, and then get some more gears before you bollox yourself.

What do you have on your BMX? And do you have excessive ligament tightness which is messing with the knee stability (notably the ITB)?

i recently swapped from 175 to 165 to 175 again on my commuter (20 miles a day)

i havent noticed any difference

I’ve got 31″ inseam and since going to 165 cranks at the start of the season, haven’t had a peep off the IT band trouble that always niggled previously. That’s the only thing that has changed on my setup so I reckon it’s a good move. But everyone is different, maybe look at getting a fit analysis done?

If I thought they might help with any knee pain I was getting then I’d just buy them and give them a go. You can always sell them on afterwards and the money lost will be less than a few tanks of fuel.

Cheers everyone.

My BMX is 175, but that was just what i had before and purchsed around 3 years ago, before i started MTBing.

Just realised my commute bike is running 170s, dont get any knee pain there, but it never gets ridden for more than 20 mins on very different terrain, but they do feel good.

chief – i know i have issues with knee stability, but never had it assessed, so do not know what the issues are. No doubt a better start getting it assessed.

No harm in trying it. I’ve a long history of minor-but-persistant knee pain when riding, and tried 155mm cranks on my Alfine-equipped bike about 6 or 8 months ago. Zero trouble since…

In fact, when I got my other bike out (175mm cranks and derailleur gears) later it felt soooo wrong that I promptly converted that, too.

Crank length of 10% of total height is a good guide for children’s bikes, so why not use it as a start for an adult?

However, I have similar bikes with 170 and 175 where I cannot feel the difference either on the road or in the singletracks.

PaulD

Otherway round to you (i’m tall, 6’4″) and I find 180s more comfortable than 175s. Some people will notice 5mm in the cranks, some won’t….

… what makes as much difference (for me) in terms on knee issues is the seat position relative to BB. Maybe you need a layback post? (or an inline etc.)

If you are having consistant pain then it is worth getting it checked out, and maybe get a few opinions. I’ve battled with knee pain for well over a year until someone finally found the cause – a painfully tight piriformis causing tracking problems. The point is muscles further up or down the chain can cause knee problems and they can be easily fixed.

I’d probably still try the cranks, because you’ll always be wondering ‘would those be better?’ And playing with your bike setup is all part of the fun. I also think you can over think crank length and you get used to what you ride.

Try a long ride on the commuter and see if that causes any pain. Then wonder if it’s the bike position, rather than the crank length?