A displacement of the suspension sufficient to halve the volume of the nitrogen in a sphere would double the pressure within the nitrogen chamber. Two chambers are linked by fluid so each would be reduced by the same amount although the drag through the interconnecting pipe will delay the response of the rear sphere. Then add in the unequal displacements front and rear for bump response and you start to wonder why you want to know! Dunlop rated the spheres to 800psi max so transients will be around 3/4 of that to allow a safety and wear margin, say 600 psi.