i was cleaning my bike with the back wheel clamped in an indoor trainer and i noticed a lot of side to side play in the rear wheel. i removed the cassette and using the mavic tool i snugged up the silver ring with the dimples in it.
however there was still some side to side play and i noticed that one side of the axle protruding from the hub was loose and i could unscrew it by hand. one side of the axle is silver and the other side is black. i unscrewed the silver side all the way by hand and then both halves of the axle slid out of the hub. i slid them back into the hub and screwed in the silver side by hand until they joined together and were snug and then the side to side play was gone. it looks like an allen wrench will fit inside the silver side of the axle. however there doesn't appear to be an opposing wrench flat anywhere to use to tighten the allen wrench. should i be tightening that down? and how?
also how tight/loose should the silver ring with the dimples on it be?
it appears that unscrewing the two pieces of the axle is what adjusts the bearings. so one way to adjust the bearings is with the wheel off the bike insert a 5mm allen wrench in the silver side of the axle and on the other side of the axle use the mavic tool on the dimpled silver ring (if you don't have the special mavic tool just grab the other side of the axle with your hand).
the easier way to adjust the bearings is to mount the wheel in the dropouts and tighten the skewer down. then you only need to use the mavic tool on the dimpled silver ring. i snugged up the silver ring against the bearings and then spun the wheel and observed how it came to a stop. i found that if i backed off the adjustment about half a turn the wheel spun easily before gently coming to a stop. any further loosening after that did not appear to enable the wheel to spin more freely.
because i discovered so much side to side play in the wheel from now on i'm going to check that adjusment on a weekly basis. i noticed the wheel was loose when i pushed on the spokes near the hub and the wheel moved on the axle from side to side. that movement caused the dimpled silver ring to stick out from the hub so that it was no longer flush with the hub. you need to grab a chain stay and then use the fingers of that hand to push or pull the spokes near the hub to see if it moves back and forth on the axle. keep your eye on the dimpled silver ring and see if that moves out from the hub.
i just checked and i don't think the two pieces of the axle can move relative to one another when they are clamped in the dropouts with the skewer. so the bearings can't get out of adjustment when riding your bike. however if you take your rear wheel off your bike a lot and also take the skewer out so that you're handling the wheel by the protruding axles then you can end up either loosening or tightening the two axle pieces which will change the bearing adjustment.
mavic says not to mess with the bearing adjustments because they are factory set at the optimum adjustment but my rear wheel was binding when i first got it from mavic and it took me several weeks before i noticed it didn't spin freely. so i took it into my lbs and the mechanic pulled out the mavic tool and loosened the dimpled silver ring a little bit and voila. my wheel spun freely like a good wheel should.