[Closed] 170 or 175 mm cranks

I've read all the theory, mainly what I know is that one of my XTRs is 170mm and the other is 175mm and I have no idea which is which, certainly can't tell when riding.

Realistically there's about | | much difference in it, can't believe you'd notice.

It's the difference between having a good new insole in your shoe or an old flattened knackered one........

165 for the cool kids !

(and me)

Northwind, really? I use different length cranks on different style bikes and do notice the difference.
I prefer 170 for MTB but I ride 165s on all my DH bikes for slightly better clearance (they all have V. low BBs) and conversly I run 175 on my roadbike and BMXs.

Dunstick, funny you say that, I almost always ride in the same shoes but have an old knackered pair of the same shoes I leave at my GFs to ride in and when I wear them I totally notice the difference with the worn sole.

In theory there should be an optimum length for your leg length and riding style (but you might still find you prefer a different length than recommended).

I reckon I might notice less pedal strikes, since the hemlock can drag its arse a little bit sometimes, but I can't feel it in the pedalling action. Switching to thinner pedals has much the same effect but few people talk about choosing the right pedal thickness for their leg length after all.

pedal thickness is a whole new can of worms. 😉

I was never comfortable with 170s on one bike (CX) with 175 on everything else - just felt wrong and gave me sore hips.

I guess my legs are used to 175s and everything had settled into that diameter - the mechanical "advantages" of 170s and 175s were clearly overcome by sheer pain and misery on long rides.

Why not compromise and get 172.5 's ?

I certainly notice it on the roadie, less so on the mtb

As said, less gives better ground clearance.

I run 170mm on all my bikes, mtb and road.

If I use 175mm I end up with a pain at the back of my left knee, although it takes a 5+ hour ride to show.

I measure up:

1) 80cm inside leg (measured in cycling shoes)
2) 58.5cm from my hip to my knee
3) 44cm from my knee to my ankle

How long are your legs?
Do you spin or grind?

If yours are short like mine & prefer to spin then 170's are perfect.

Like Amplebrew I used to get very sore knees afterlong rides or when using the big ring alot.

They are also better if you are recovering from any knee surgery.
I had a new ligament.

I only made the change this year after a conversation with another rider
who said that 170's might be better for a shortarse like me.
Big difference .No knee pain.

Small con is changing the cranks on all your bikes.
i took a full suss abroad for a week and forgot to change from 175 to 170.
No problems whilst there , but my knees where vvv bad the week after.
J.

170 on my MTB
165 for DH
But both my road and BMX bikes still have the 175's they came with and niether feels quite right, will change both to 170 some day.

Van Nicholas have a size of everything calculator on their website

certainly notice it on the roadie, less so on the mtb

As said, less gives better ground clearance.