We had 10 different bikes, from cheapest with Hi-Ten steel frame and Shimano Alivio equipment (King Fox, Olpran, Author) over some bikes with Shimano Deore LX and CrMo frame (Mongoose IBOC COMP, SCOTT Boulder) to Deore XT on Alu frame (Author VISION, Heavy Tools, ProFlex). Two bikes had stems with suspension, one was full-suspension.
Two broken rims, one Rigida and one Mavic 231, on both was ripped off side wall.
Two damaged freewheels, one quite new cheap Shimano, the second older Deore LX.
One pedal bearings, nothing serious.
Two damaged tires.
About five punctures in tubes.
Repeated problems with bags, especially their holders.
Sand and water in bearings on cheap older equipment.
For a wonder we had no problems with racks, all bikes were equipped with front and back rack, mostly Czech Sport Arsenal from steel thin-wall tubes with a couple of exceptions, as steel noname, Alu etc. Bigger problems were with rack bags, we had some Sport Arsenal, they have adjustable volume, are partly waterproof, but they have very unreliable holders on rack. Another bags from Czech producers Montan Sport, Testudo and Pigcon hold reliably, but are not waterproof. All things inside these bags were in plastic bags, but these were damaged soon... One model of American bags did fall very often, it's plastic lock was not secure. Author bags ripped soon, fall off often and were not waterproof. The only bike with Ortlieb was that with broken rim, which didn't continue in trip. Reputation of Ortlieb is the best and after looking into them I believe it - waterproof and reliably attached.
One problematic thing is chain, in sand greasing is not very good idea, ungreased chain isn't nice, too.
Pedals - I prefer classical for so that use, SPD and similar I don't consider to be suitable for expedition, where you must count with some walking or hiking. Especially in sand there is a problem with shoe locking and unlocking.
Tires - in interior are roads very sandy, so wide tires are necessary, I afraid many punctures on our trip, but all was normal.
Suspension - it is pleasant, but with heavy loaded bike in sand I have two reasons to prefer bike without it: 1. bike especially with back suspension is not so stabile and ridable with load on racks, 2. racks are on stationary part, suspension doesn't save wheels and spokes from baggage shocks, it is only pleasant for biker, he can go faster and damages wheels supporting baggage weight easier than on bike without suspension.
Frames - both
non-suspension Alu frame users considered their frames to be too
hard. One of them said after trying CrMo Mongoose IBOC COMP with
high satisfaction, that there is a big difference. His Alu frame
doesn't absorb vibrations, Mongoose is better from this point of
view. But Mongoose is maybe more soft, than is efficient. I am
very satisfied with my old CrMo Scott Boulder, it is a little
more heavy, but very stabile and comfortable frame.
(Will continue later. Maybe.)