Did you installed a doble Damper for your 40's or how did you manage to Balance those, my respect for you. (i Should make another Thread for this question)Yeah with a marginal pump or steering box big tires will definitely kill them. I had to upgrade to a psc rebuilt box after I installed 40's. You gotta figure the fluid will heat up and thin out more too which will allow it past the seals. Plus the increased resistance and force on the snout of your box trying to control those tires, if there was any slop there, big tires only makes it worse.