paul krige

what I have been told is that a 10 speed crank will probably work but the gauge of a 10 speed crank is narrower than a 9 speed crank and there could be lateral play in the chain ? Sounds very technical to me but a number of people have said they would not recommend it because of the narrower blades.

Does anybody know for certain whether a 10 speed compact crank will work with a 9 speed system ?I have a Shimano 105 9 speed 172.5 and want to convert to a compact crank 172.5 but Shimano apparantly only make compact cranks in 170 and 175 in 9 speed but they do 172.5 in 10 speed.Anyone know where I can get a 9 speed crank ( in Shimano 105 price bracket )