Outer Limits 4x4 Board

I run reversed steel disco rims with 34 x 10.5 inch tyres. Below approx 1200 revs the steering is particularily heavy. Above this the steering is fine. Obviously the engine is not ticking over fast enough to drive enough fluid through the power steering system. Does any one else have this problem? What fixes are suggested?

Have you checked the hoses for blockage? If there is an obstruction it could be that it needs to work harder to get the required amount of fluid moving.
Id start by looking at that, then if it is all clear Id look at the possibility of rebuilding the pump.
The pump could also just be struggling to turn your tyres. Perhaps a larger pump might alleviate some of the stress?

32 10.5 mongrels on series offset rims, at idle(700rpm) and with a
13'' steering wheel i can palm wheel full lock both ways.

to me it sounds like your box might be rooted or close to it.
when was the last time you changed the PS fluid??
put new fluid in and add one of thoes additives and see if theres a differance. i doubt the pump would be dead.

the worm gears in the box wear making the box less efficent
eg bypassing to much pressure.

my 2c

good suggestions thank you. I have rechecked today and the stiffness is probably more like at revs up to 800 rpm not 1200. What would cause a blockage in the pipes?

Its not only the size of the tire, but its the pressure therein and the surface you're on...

I'd sugegst step 1 to check the OEM stuff if they are running well or not, step 2 would be to include all the tiny tricks to make the pump perform better, and step 3 would be to add a hydro assist ram...I'm there with the ram for my 36x13.5 Iroks, but when the 42s go on, I'm going full hydro...