Is it important to use the washer on the valve stem? I just got cxp33's and because the top of the rim is more aero than my previous rim, I notice that the washer doesn't fit as good as it did on my older rims. Any reason why I should leave this on? Thanks.

Nope. None. Leave it off.

__________________
"I am two lesbians in a man's body."
--Eddie Izzard

First, baby powder the tube. Makes it last longer and easier to install. Tubes move around inside of a tire when riding. If you don't powder or do use the nut, it can either stick to the inside of the tire causing a flat or tear the valve if you use the nut.

Powder and don't use the nut.

I'm not familiar with a valve stem washer. What is it?

Automatic device that saves you the trouble of washing your stem by hand.

Ha ha! I think they are referring to the round threaded stem nut...

My mechanic advised against the powder "trick" when I brought up that I use it on lightweight tubes - I think from memory the reason was that some powders can attack the tube material? May be arguing one old wives' tale against another here, so I won't pass judgement...

Cam

If it's safe for a baby's but, it isn't going to hurt a latex tube.