I’ve been riding a UST setup this season and I’m not totally happy with it. Supposedly UST tires combined with UST rims should be airtight without sealant… so far that’s definitely not the case. My rear tire definitely holds air better than the front- probably good for about 8 hours before I start noticing it’s lost any pressure- the front on the other hand is only good for about 2-3 hours so I often have to add a little air mid ride. Trimming the little bits of excess rubber from the tire bead helped but I’m still not getting a completely airtight seal. The bead seems to lock into the rim really well- breaking the bead once installed is pretty tough but no luck getting a really good airtight seal. I’m currently thinking of trying a different set of UST tires to see if there is any improvement. If that proves fruitless I’ll be considering going back to tubes or dealing with sealant.
I have UST rims, but opted to go with tubeless ready tires (Schwalbe) rather than UST. I used Stan’s sealant have never lost any air pressure. Having to re-inflate mid-ride doesn’t sound like fun.
Gtrguy - you shouldn’t be losing much with UST. I’d throw in a little sealant just to seal up any pinholes that might be there (lots of people do this even with UST).
I prefer “ghetto tubeless” - that is a ZTR type rim and a tubeless ready tire - it’s quite a bit lighter than UST (typically), and usually cheaper. For what it’s worth I find I’m riding 3-4 rides before I add more air. That’s with non-tubless ready tires and some “Orangle Seal” sealant.