After a change of plan I am now left with a pair of new Schwalbe Big Ones (60mm / 2.3) and am wondering how safe it would be to run them tubeless on Archetype rims (internal diameter 17.5mm I think).
The rims are not officially tubeless though have a tubeless type design and Malcolm at thecycleclinic who built the wheels states on his website that he feels they are essentially tubeless rims (or words to that effect).
Are they too wide to use safely (certainly too wide on some compatibility charts) ?
I cover some road including a fast longish downhill before any local soft stuff so would ideally run pressures above 20?
Not tied to the idea of using them, just might be a fun alternative.

Are the rims already sealed with tape, and fitted with tubeless valves ?

If so, then you might as well try installing the tyres without tubes, using some soapy water and see how good the fit is. The ideal fit is when the tyre beads ‘pop’ into place with only about 40/50 psi. If they’re too tight (all tyres and rims vary in diameter, so it can be down to luck) then you might need a compressor to get them to pop into place – in which case, don’t bother, just run inner tubes.

And if your rims haven’t yet got tubeless tape/valves, I’d just buy tubes.

I’ve run 2.35″ tyres on Mavic 317 rims, but needed at least 35psi or the tyre was a bit ‘floppy’.

You mention something about ’20psi’ in your post…forget that. If you’ve got DH wheels and tyres, then you might get away with such low pressures, but not for normal riding. And you’re looking at slick tyres right ? Then what use is low pressure ? Good luck 🙂

Yes they mount fine with an airshot with very minimal loss even without sealant.
(I was previously running the rims tubeless with 35mm tyres)
I guess my concern is that with higher pressures on the road eg 40 then would the risk of coming off the rim be too high (eg cornering downhill at any speed)
I’m less worried about it happening at low pressures on the soft stuff as injuries would be less severe (probably).

pinkbike article

I’d suggest youll have a pretty unreliable bead. I ran a spline m1700 for a season and i was forever burping a 2.4 rubber queen. Mostly high speed cornering and sometimes even just accellerating hard through the pedals would kill it off after a couple of cornering burps. 17mm inner width rings bells on that wheelset. I had to run muc higher pressure than i wanted to keep it from burping.

Thanks interesting read. The more I think about it the more I feel its a bad idea to run this combination on the roads.

Used to run 2.35 mudmads on xm317s, would need >35psi to stop them rolling off the rim on tech/fast descents.

Similar problems with fat albert 2.35s on xm819 (UST), too low and they would keep burping.

If this is mainly for road riding, can you not just go for 1.75″ or 2.0″ ?

They are left over from a previous idea.
I’m calling chicken on myself and am going to run them tubeless on my Charge Saucer rims instead..20mm internal so should shape better and be safer. Thanks for the advice.