Hi, thanks all, looks like some good options. The sensible option seems to be to stick with 385/65/f22.5 in one of these. However bit of a nagging doubt that the top end manufacturers - Unicat, Actionmobil etc all still seem to sell their trucks with r20s. Appreciate r20s aren't that easily available, but can air down more and to Charlie's point with 2 spares and given tyres seem to last a while, is there much experience of people going through 2 - 3 tyres (ie to the point they get stranded with 2 spares)? Do R20's feel similar to R22.5s when at normal pressures on road ?
I lost a tire in Baja in 2007 due to an aftermarket shock breaking in half and eating out the inner sidewall. I had only 1 spare (I had several spare OEM shocks) tire so I had to cut the Baja part short.
In Tucson a tire place found a used 395/85R20 XML with unknown provenance. It blew out at 10mph in Saline Valley.
That’s why I carry a second unmounted spare.
And the question of 20” bead retention: Mysteriously Mercedes forgot to install the ordered internal beadlocks in my original wheels. On the maiden trip I got stock in a very muddy place in Morocco in 2006. Using CTIS I got the pressure very low. I almost immediately experienced debeadment in an axle, I forget which. Fortunately we were with 2 other vehicles and Unicat people so it all got fixed. I got the beadlocks after I expressed outrage to Mercedes but didn’t install till I got Hutchinsons in 2015. Now I have no worries about bead retention.
Big XZLs ride well on the highway but have speed ratings of only 55-68mph. The new 395/85R20 XZL2 has full load speed rating at 68 and up to 75 with slightly lower load. And they exist in North America. Might get a set next year since Namibia and Botswana tend to be on the warm side.
For me any 22.5 would be quite unsatisfactory, even 445 XZL, since I use CTIS a lot when off pavement and pressure down to 15 psi in front and 32 in rear are a big part of getting unstuck without using winch. On highway I run 64 front, 95-100 rear.