anyone tall decided that this was worth doing? I definitely noticed the 5mm between 170 and 175. Is it a case of: 'if you are 6 foot 4 inches + then you probably should but it wouldn't make a huge difference to speed/fatigue if you didn't'. that's my answer to myself so far…

If you use 180's on an MTB maybe.

correct. Or you have to be someone powerful like Miguel Indurain or Tom Boonen (both ride 177.5) to get the most cadence and power (lovely french word souplesse(sp?)).

I ride 172.5 on the road – just to be a bit different again.

If you noticed the 5mm (I didn't), Shirley you'll notice the 2.5mm?

yep…. do it! Just have to watch your ground clearance!

I ride 172.5 on the road – just to be a bit different again.

Different to who? 172.5mm is 'standard' on the road, as 175 is on the MTB.

If you spin, I wouldn't bother, if you mash then go nuts!

hmm interesting! i'm leaning toward a point of inertia, with your help!

whats darkside???????????

If you spin then 175 would be fine… If you grind top gear all the time then you need the extra leverage…and blow your knees appart 😉

njee20 – different from the OP 😀

I've road raced for years. I know 170/172.5 are the popular cranks.

I've had a 177.5 on my tt bike for a few years and found it to be ok. Just about to change to 172.5 to try reduce the hip niggle I've got.