I wouldn't be too worried if I knew the coating was sound and I kept a good distance
These hand wash businesses where they use a jet wash always use the lance far too close to paintwork in my opinion
I think you're absolutely right, Stewart. The pressure gradient in the water spray is very steep, in that the water stream rapidly loses its power once it has left the nozzle - for evidence, simply point your pressure washer jet vertically upwards, the water really doesn't very high at all.
But when used at close range, by which I mean less than a foot or so, the destructive ability of the water is immense, it's easily capable of damaging surface coatings, even those in good condition.
I think the reason why people advise against their use is that there's too much risk of damage if you get too close, but in reality if used sensibly they can be very effective.
I personally don't use a pressure washer on my Morgan, I clean my wheels in the garage by lifting the car up and putting a large greenhouse tray under the wheel to catch the run-off. I then give them a good spray with one of the many APCs that are available (I currently use Bilt-Hamber Surfex cleaner) and then poking a wire wheel brush into the gaps between the spokes. Rinse off with water from a small pump-up plant sprayer, a quick squirt of aqua wax, wipe off with a microfibre, and I'm done. Takes around 5 minutes per wheel.
