Dirt bike tyre valve stem nut

[A&R]

Hopefully some learn-ed person here can tell me if it is better to leave the nut around the valve stem done up tight against the rim or left loose so it can move? Note the tyre is bolted to the rim anyway in two places but they do move. Especially when we let the rear down to about 7psi for the slippery stuff. There is a tube in the tyre as well obviously not bolted to the rim so is this the reason they leave the valve stem loose? so tube and tyre can move?

I ask because I had new tyres fitted to mine and my sons dirt bikes and they came back with the nut left loose against the rim but with a stem cover on so it couldn't come off. Is this correct? and why?

[cynna]

the nut is supposed to be left loose - just so there is a bit of movement for the tube so that the valve doesnt get ripped off

i read it in a magazine recently - i think that was the reason they gave

[cynna]

here we go - trailrider #12

"wind the lock nut back up to the valve stem cap so, if the tyre spins on the rim, it has room to rotate. if the nut is wound down against the rim the valve stem will be ripped from the tube if the tyre spins on the rim and your have an instant flat"

[merv]

Leave it loose and you'll aslo be able to see when it moves a little bit as the stem will tilt over and you can fix things before it does rip the stem off.