Any suggestions for strong machined rim?

You can give your rims a occasional clean with an ink eraser (one of the gritty rough ones) to remove crap that will turn into a grinding paste in the wet and it stops rims getting hot when heavy braking. Instantly made a difference to my braking power too.

http://team-machin-e.blogspot.com/2010/08/protip-wheel-maintenance.html

Good advice^

Also, checking your pads for shards of metal regulary can help too.