all the quad guys at my mx club run 4-5 psi with rim locks and that works well(myself included)
be careful running low with out rim locks.
depends what your terrain is as well but as i see it the lower the tyre pressure the wider its tread pattern and the more grip youll get so more drive less wheel spining.
from factory i had 7.5psi and i noticed that if i came in a corner to hot the wheels were so hard they would keep spinning and i would spin out , when i lowered the pressure and tried the same scenario the bike drifted the corner great squared up and hooked up and off i went
Thanks for your input guys! I will try it out this weekend. I do run beadlocks in the rear so I will play with it a bit. I did notice the same thing, too much pressure in the rear and I would spin too much through the corners especially if it was just watered or real muddy!
this is something I get asked alot at the track, it is also tire brand specific.
Anything less than 4 to 5 psi in the rear and you get excessive tire carcass roll, this actually peels part of the tire up as the side wall on the out side rolls under. upping rear pressure 1 - 1.5 psi in the rear can have a significant influence on corner behavior normally significantly improved. Front turn in is improverd with higher pressures but the ride quality drops away (this is where after market shocks really shine)
I range from 4 to 7 in the rear and 5 to 7 in the front. Holeshot MX's like more front pressure but are a very harsh tire due to there stiff sidewall. the stock maxxis is a bit of a marshmellow, but nice and comfy for XC at 5 - 6 psi front I haven't tried these at higher pressures, most of the time the stock rubber is in the tire rack with holeshots on in preference.