Is there any difference in a 170mm crank and a 185mm. The crankset i ahve at the moment has 185mm crank arms and im looking at buying another which is 170mm will this matter??

You may notice that much of a difference. Or then again you may not.

I ended up with some 170’s and once I Noticed they had 170 stamped on the back, I decided they were the reason I struggled up the hills. I still struggle the hills, but now I know it’s just me. Saying that a 30mm overall difference is quite a lot, so maybe you will notice it

If you look on some of the dark side forums you will find that there is a calculation of inside leg length to crank length. My guess is that for 185mm cranks you should have an inside leg of around 34-36″ 175mm are regarded as “standard” for Mr average height.

I think there’s a tendency to have longer cranks on mtbs. I ride 175 on the mtb and 170 on the TT bike. These bikes feel so different for too many other reasons to be able to say I can feel the difference in crank length.

pffft! Here’s my opinion, take it as you will.

If we forget singlespeed/fixed bikes for the time being….

Crank length on the road for a mere mortal makes very little difference. You can spin faster with shorter cranks and crank harder with longer cranks but for most of us, the gears take up the difference.

Offroad the same applies but longer cranks are prone to hitting trailside objects like rocks and tussocks. If your bike has a low BB then long cranks would be a bad idea, assuming you ride in places with lots of high things but ultimately it comes down to your height and riding style.

But at the end of the day if you’re a normal person who just rides for fun, it’s not going to make much difference at all. From experience I’d say 170 is the best of both worlds, 185 seems a bit long and should only be for people with inordinately long or weak legs.

I think you’d notice a 15mm difference if you rode them back to back. But you’d get used to any length eventually.