Crank lengths - 175 vs 170

Will I feel the 5mm difference? I've generally always ridden 175mm cranks as they seem to be the default, but have a set of 170mm cranks on my little used Saracen so haven't really felt any difference on the short rides I've done. Will longer rides be any different?

Well it is only 5mm...

That said some folk absolutely swear they can tell the difference, with the longer cranks providing more leverage but perhaps less spin?

I think if you went from 175 down to 165 it would be apparent.

Steven

BiTD my riding buddy had a mismatched pair of DX cranks (170/175) and it took him months to figure out that there was something wrong As far as I know, he doesn't have any orthopaedic issues, so maybe it is all in the mind? Hell, if people bought oval chainrings.......

I bought some 175mm XT cranks, they arrived and they were 170mm/175mm.
I had bikes with both and thought I could tell the difference, but on later inspection one has a 28T granny the other 22T.
Anyway I sent the cranks back, turned out the seller had been riding with them since 1997 and never noticed the length thing;-) But if I had used them I would have known.
I have pair of Truvativs, I use the word pair loosely as one is 165 the other is 175 I suppose I should try them.

It'll depend on you, your height legs etc, but since you have them... You know how to find out.

They'll not kill you.

It's not about leverage, it's about making a comfortable circle path for you leg length.
If you're average to small, probably no problem or may be better.
Given lanky legs then you should be towards the 180 side anyway.
They do make them in 2.5 mm increment for the top end for a reason, but doubt that applies to you or me.
Any it's a bit like frame size, one is better for you but you can still ride either side sizes or even small child bikes, it just not as comfy (it's also why child bikes have shorter cranks)

Read what Sheldon Brown wrote on this subject; you won't worry after that.

I have 170 mm arms on my road bike, 175 mm on my mountain bike and I don't know the length of the arms on my trekking bike. I've never felt any difference...

I have 170mm Turbines on my '97 Altitude and can notice a difference with the 175mm's on all my other bikes, but I can't find any negative impact at all. This 10mm difference just forces me to shift down earlier on hills, but on the other hand I can have a higher cadence on straights. Oh, and you might need to put your seatpost 5mm higher. So effectively if your perfect frame height would be 18", you now need a 18.2"

Thanks, seems like I'm worrying over nothing.

I rode a mismatched pair of 175 / 170 cranks for 3 years, and never had any issues.