I have a 1996 Dodge Ram 4x4 , it came with P225-75-R16 tires, I am thing of replaceing them with P285-75-R16, before I do with this mess up anything, a friend says it can screw up things, what things. I just wanted to do this to  butch it up a bit.

Changing tire sizes can affect many things.
The height of the factory tire was determined by cost and room under the fender.  You're wanting a much higher tigher.  This could cause the fender well to come down and scrape/cut the tire.  It will also screw up your speedometer/odometer.  If you do this, you need to get a gear changed in your pumpkin (speedogear).  

Check with a tire retailer and they will give you all the facts.  Then try to sell you what will work.  You might try talking to a truck customizer who odes this all the time about other factors to be awaare of.

TXLEWIS

Your new tires will be 2-3inches too tall 7 your speedo will be off by +7mph

you need a shorter sidewall(lower aspect ration) to go with the increased width

like a 285/60/16 or a 285/55/17

here are some good links

[url]www.tirerack.com/tires/tiretech/general/utqg.htm[/url]

[url]www.miata.net/garage/tirecalc.html[/url]

[url]www.secret-secret.com/turbo/DIY/tirecalc/turbotire.html[/url]

[url]www.4lo.com[/url] you might like this one

[url]www.c5-corvette.com/tirecalc.htm[/url]

[url]www.dsm.org/tools/tiresize.htm[/url] this one gives size recommendations