How low can you go with UST tyres pressures whilst still maintaining some tyre stability & burp resistance?
FWIW, the rims are XT UST's and I'm thinking trying 2.2" Rubber Queen UST's (noticed that Conti recommend 58psi max and 45psi optimal - I'd imagine they'd be pretty skitty over rocks at 45?!)
I'm using dt ex500 rims converted tubeless setup with dual ply highrollers. I know this isn't UST, but I run those around 30psi with no problems at all.
I've run stans 355s and tubeless rubber queen 2.2s at about 10-15 psi and they were grippy as anything.
Although it does depend hugely on how much you weigh. Usually I run them at 20-35psi depending on what I'm doing.
Just a little rule with regards to Contis tyre pressure recommendations: ignore them completely.
I've run stans 355s and tubeless rubber queen 2.2s at about 10-15 psi and they were grippy as anything.Now, I am a bit of a one for low pressures, but that is super low! - nice one
I hadn't thought about the weight variable......duhhh!! I'm about 88 kilo (13+ stone) in full riding kit, so I guess I'll have to run a bit more pressure, but encouraging that you're able to drop down from 20-35 to 10-15psi on 355's (the XT rims I have are a similar width to my wifes 355's).
Running at 10-15 psi?? Beside getting pinch punctures do you not think that cornering will be rather rubbish at such low pressures. I have always found that tyres squirm all over the shop at anything under 30 psi.
Guess a lot depends on tyre width, terrain you're going over and how you ride, and of course, your weight (I know some female XCers who are sub 50kg!.....I've eaten sandwiches that are nearly that weight.....and you'd never guess 
).
Depending on what & where I'm riding, my non-UST 'Stans method' tubeless tyres are usually somewhere between 20 to 30 psi.
Don't know whether it's the method I use to mount and seal my non-UST tyres, but when I come to change them, they're usually quite well 'gummed' onto the rim. My idea of trying proper UST tyres is to avoid mess and speed up tyre changes, so if possible I'd like to experiment with no sealant. However, I wasn't sure whether I'd be running the risk of burping or folding the tyre off the rim at sub 30psi - hence my initial post.
On my Alpine 160 on flows I run minion 2.5 dh UST at around 18/19 psi - feels spot on (HR on the back at 28psi)
On my Soul I run a crest front with a Shwalbe fat Albert evo 2.25 at 25psi and same tyre on rear but on a flow rim at 29psi
No point converting to tubeless if your not going to benefit from decent tyre pressures.
I usually run 25-30... Anything below that and it's just constant rimstrikes on anything rocky in my experience. I'm not heavy either. Depends a lot on how you ride and where you ride I'm sure.
I'm running 2.2 Rubber Queens on one bike and 2.2 Bonty XR4's on another, 21-23psi front & 30-33 rear on both bikes, 92kg ish. I find if I go below 20psi on the front it starts to feel a bit squidgy, and above 27psi starts to feel a bit skittish and less grippy. My riding is nearly always hard pack trail centre type terrain, where in my opinion, tyres need to deform a bit to find grip on stony/rocky surfaces.
95kg riding weight here too. Regular rubber queen 2.2 and 2.4 X-king on stans with yellow tape. I run them on my 5spot at 30 psi front and rear. I can't get away with any lower without picking up damage on the rims and sidewalls.
If they had sturdier sidewalls I'd run a little lower, possibly down to 25psi.
No point converting to tubeless if your not going to benefit from decent tyre pressuresYes, exactly my thoughts. If the UST RQ's were a lot cheaper, I'd take a chance. However, at £80 a pair, I thought I'd do a bit of research first - 'cos, as you say, if they can't be run reliably at low pressures, it'd be a reet waste of money.
Thanks to all for responding - From what you're saying, it sounds like they'll be fine in the 20-30 psi range.
p.s. Scienceofficer, just out of interest, do you run the RQ and X-King as a front & rear combo? I'd wondered about an X-King on the rear, but wasn't sure how they sized up (guy at LBS reckons the 2.2 X-Kin is a lot smaller volume & width than 2.2 RQ(?))
Yes, thats how I'm using them. The 2.2 X-king is tiny compared to the 2.2 RQ. I sent mine back and had to get a 2.4.
The x-king is pretty good and has a fair amount of grip, but its not as fast as I'd like - Its not slow, but its no Maxxis Aspen.
IME, about 10, maybe 15psi less than you run similar/the same tyres with tubes. For me that means about 25-30psi. Any less and they squirm/roll around which I hate but then I weigh more than most people so obviously the exact numbers will depend on you.
13st, Stans Flow rims, 2.4 RQ front - 20ish psi, 2.4 Big Betty rear - 30ish psi.
Other bike has 819 UST rims with 2.35 UST tyres and I run them at similar pressures.
Running at 10-15 psi?? Beside getting pinch punctures do you not think that cornering will be rather rubbish at such low pressures. I have always found that tyres squirm all over the shop at anything under 30 psi.
Pretty hard to pinch without a tube.
I was running those pressures in the Alps, where we were didn't have many hard corners, so I didn't find any problems with squirming. My mate who is proper good runs dual ply minions 2.5s or something with dh tubes at about 8psi when he's out there, and he's quite a bit heavier then me. He's super smooth though.
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