I am new to offroading an am looking at buying a used xterra. I know that I will want to put on off road tires but do not know anything about tire and wheel specs. Can someone explain this to me? What so all the numbers and letters mean. Also do I have to change from the factory wheel to a biger stronger wheel or can I leave it alone. This is what I've been thinking about doing once I buy the X. I think that if I really want to off-road. I will need 32" tires, a 3" Suspension lift and a winch bumper to accomodate the larger tires up from but I have no idea what to look for in a tire or what the numbers mean. Someone please help.

Welcome aboard. Not much that hasn't been said here already if you take some time to review the older posts, but here's the basics...
Factory wheels are generally best for allowing the most options in tire sizes. For your 2000 w/ 15x7 wheels, a 32x11.50-15 tire is an excellent choice and can fit without a lift or bumper, you just need to trim away some plastic to clear the front tires and possibly raise the front end with some torsion bar cranking, I've run that setup on my 2000 since 9/00, no lift at all.

Here's a good reference on tire specifications: http://www.tirerack.com/about/techcenter.jsp

Brent

Thanks offroadX. I read over one of my last posts and realize that it sounded very missleading. It sounded as though i already have an X because I have found one and am actively pursuing purchasing it. I am already talking about it as though it is mine. I have been reading through many of the posts up here and getting an idea of just what it is capable of. I was just having a little trouble finding out what all the specs mean. I did a search and came up with few things but was getting more confused because some people use different terminology for the same thing, I think? Anyway thanks for the link and I'm going to look it over now. I'm trying to figure out how much the truck and the mods are going to cost me. I also want to put on the Calmini bumper and front skid so I will probably need a beefier suspension. BTW can I offroad with the stock truck or is it not recommended. Thanks.

Thanks offroadX. I read over one of my last posts and realize that it sounded very missleading. It sounded as though i already have an X because I have found one and am actively pursuing purchasing it. I am already talking about it as though it is mine. I have been reading through many of the posts up here and getting an idea of just what it is capable of. I was just having a little trouble finding out what all the specs mean. I did a search and came up with few things but was getting more confused because some people use different terminology for the same thing, I think? Anyway thanks for the link and I'm going to look it over now. I'm trying to figure out how much the truck and the mods are going to cost me. I also want to put on the Calmini bumper and front skid so I will probably need a beefier suspension. BTW can I offroad with the stock truck or is it not recommended? Thanks.

You don't need to beef up the suspension with the bumper and skid. If anything, better shocks would be where to look to handle a little more weight that way. If you add a winch though, the torsion bars will start to feel the hurt.
Tires and armor, plus something to beef up the steering (L&P, Calmini, and SLR all offer solutions) would be the basics and you can wheel it pretty hard with little concern.

Hello,
There are 2 types of sizing most commonly used in USA. Floation type as in 32/11.50/15, which means 32 inches tall, 11.5 inches wide and 15 inch wheel size (the hole).
The other is called p-metric as in 265/70/16, which means width is 265mm. The next number is called the aspect ratio, simply it means the sidewall is 70% of the first number. The last number is the size rim in inches that the tire fits on.
Both of these width sizes refer to the widest point across, usually sidewall to sidewall, not across the tread,( it's usually narrower).
Hope this helps.
P.S. i only know this because i sell tires. Archer

Thanks, thats exactly what I wanted to know. I was trying to figure out the difference between the two systems. I think that the first one is a lot easier.