Originally Posted by phidauex

5mm isn't much, but a 165mm crank has 3cm less travel per revolution than a 170mm, and that is a noticable amount.

Also, a bike with 70mm of BB drop, and reasonably long platform pedals (shoe to shoe outer measurement of around 378mm) will strike at 25.6 degrees with 175mm cranks, 26.8 degrees with 170mm cranks and 28 degrees with 165mm cranks.

velocity = sqrt(9.8 * radius * tan (lean angle)), in meters, seconds and degrees.

That puts your max turn speed around a 12m radius at 16.75, 17.24 and 17.69 mph for 175, 170 and 165 mm cranks, respectively. Sure, 5mm isn't much, but that is a meaningful change in max turn speed, nearly 1mph between 175 and 165, all else being equal. You'd have to lower your Q by 20mm to equal the change achieved by lowering crank length by 5mm. Both methods will have the same effect, but crank length or BB drop gets you more turning speed per mm of change than Q.

*puts away his engineering calculator*

peace,
sam