Mountain Biking - What size stem do I have?

I have an '06 Rockhopper comp disc, 19" frame. I have been suffering from a bit of neck pain. I'm 5'11". I replaced the riser bar with a straight bar and that has lessened the pain a bit. I was thinking getting a shorter stem might help, but I know not what size stem I have to start with. Now, it could be my body is not use to riding yet. I just started MTB'ing(AOLese?) 2 months ago and carry about 20 pounds in my camel back. My rides are usually about 2 hours long. Any help would be greatly appreciated.
mick

I have an '06 Rockhopper comp disc, 19" frame. I have been suffering from a bit of neck pain. I'm 5'11". I replaced the riser bar with a straight bar and that has lessened the pain a bit. I was thinking getting a shorter stem might help, but I know not what size stem I have to start with. Now, it could be my body is not use to riding yet. I just started MTB'ing(AOLese?) 2 months ago and carry about 20 pounds in my camel back. My rides are usually about 2 hours long. Any help would be greatly appreciated.
mick

Measure the stem with a rule from the handlebar (the gap at the bolt face plate) to the center of the cap bolt on the steer tube (hint: it's right under your nose ;) ). The length, in mm, is the length of the stem. It's likely a 110 mm or 120 mm stem with a 5 degree rise.

But the stem may not be your problem. What are you carrying in a Camelbak that gets it up to 20 lbs! If you are carrying clothes and tools and a whole bunch of other junk in there, get it off your back on onto a rack! Sure it might not look as cool but it will save your neck some pain.

Thankyou now all I have to do is find a ruler. What do I carry?
Camelback blowfish
3 liters water
Alien 2
leatherman(for the plyers)
Extra tube
Extra Slime
Pump
Wallet
Stinger(flashlight)
P-89 + 1 Mag
Long sleeve shirt
Power Bars
My ride today was a little bit better, clipless pedals have helped make the rides shorter.
mick

Nice Ruger. I had one a while back. I really don't see why you need another magazine. That won't stop a bear and it's doubtful you would see the cougar/mountain lion until it's too late to shoot.Maybe you meant the one included in the weapon, if so,sorry. Maybe sub out the flashlight for a head lamp, like backpackers use or better yet a light system that mounts to your handlebars. The water is your biggest weight and in the desert I see little chance of riding with less. Just make sure you are not overpacking. If you must have a large "what if" overage of water, food and clothing think about the previous posters idea of a rack. Dropping the roscoe would offer the most weight savings aside from the agua. Are you absolutely POSITIVE you need it?

Thankyou now all I have to do is find a ruler. What do I carry?
Camelback blowfish
3 liters water
Alien 2
leatherman(for the plyers)
Extra tube
Extra Slime
Pump
Wallet
Stinger(flashlight)
P-89 + 1 Mag
Long sleeve shirt
Power Bars
My ride today was a little bit better, clipless pedals have helped make the rides shorter.
mick

Until I read what Jameson had to offer, I was clueless as to what a P-89 was but, I have to ask, do you need to pack a gun for! I've been riding bicycles for nearly 30 years, including multiweek self-supported tours in the Colorado mountains and I have never run across a situation where I thought I needed a gun! Hell, I've never run across a situation were I needed a stick!

As for the rest of the stuff, leave the extra slime at home, put the pump on the frame and get a smaller pair of pliers (the Leatherman Juice P6 is a good choice).