Firstly the crank length is measured from the centre of the BB to the centre of the pedal spindle so the ruler isn't lined up with the pedal hole by about 10+mm. If it lined up properly I could be convinced that they were a 175mm crank possibly but I do agree that is seems longer than the 170 you say it is. Get a longer ruler. On second look I think you'll be surprised when you line it all up properly. I'd buy 170mm.I have a set of 170mm Affect R cranks. I don't see how they can be correct.