If you are riding on really rocky terrain, how much pressure should i leave in my tires? I am riding a 400ex and my friend on a 300ex...the rocks are around football size...and advice? thanks.

 

well keep the fronts how they are and lower the rears till it is easy to push in the ***** or when you sit on it and it sinks about a inch!

 

You didn't say what kind of tires you are running...if they are the stock Ohtsus, which have a rather thin sidewall, you'd be well advised to run six psi all around to minimize sidewall damage. Actually, I run six psi on my Bandit XC's which are very stiff in the sidewall area. You'll find that pressure in this area will give you better control in cornering by reducing understeer & rollover of the tire and more protection from rock damage in hard riding.
I check my tires before every ride with a digital gauge. You can't possibly determine correct pressure any other way with any accuracy. A one or two pound reduction in pressure can make a noticable difference in handling. If you think about it, two lbs underinflation is 33% less than six psi.!