In almost every full power situation, the tires will break traction before any relief valve has a chance to pop. At part throttle, it is possible to overpressure a hydro and most of them will just growl at you until you back off or jack up the throttle.smaller the tire, easier for the trans. to turn! increasing torque applied to the ground! sacrificing traction and top speed!
Under full load conditions it makes no difference on tire size to the trans./ the trans is at max torque output!
I'm no expert on hydro trans but I assume there's a bypass pressure relief valve, once that is being opened all else is a mute point!
maybe one of the hydrostatic guru's can enlighten us both!