runrideski
My partner had a crash yesterday.  She got caught in a rain rut on a fast turn on a crushed gravel city pathway.  I was in front so I missed the crash but could see where she hit the side of the rut and washed out.  She said that it caused her front end to jacknife and threw her sideways.  Her handlebars were twisted about 15 degrees.  So she landed on her side and is scraped up but relatively unhurt.  No damage to the bike either except for a small tear on the saddle.

By the time I got back to her, she was upright beside her bike and we noted a hissing noise.  We found about 6" of the tire bead had come 'unlocked' on one side and there was some small gravel wedged between the inner side of the rim and the outer side of the tire, meaning I wasn't going to get the tire to seat properly without a tube.  It wasn't an issue other than the mess, to dismount the tire (can be done tool-free), clean out the Stans and gravel bits and get going with a tube installed.  Re-seating the bead with a minipump wasn't much fun ;-), but it gives me some confidence that the tire fits pretty tight, at least once seated.

My concern is that the tire came unseated prior to, and may have partially caused, the crash.  Obviously we want to have confidence in the stability of our rim/tire combination.  We chose the 'race' version of the WTB Nanos according to others' comments that the tubeless version would potentially be too tight (thus not field serviceable) on Stans rims (which, it is my understanding, are designed specifically to allow non-tubeless tires to be run tubeless).  We've been running the tires @ 30F/32R psi, which is about as low as possible an still avoid bottoming out on some of the gnarlier/rooty sections of trail we often encounter.

I'm wondering if others have had any similar experiences they'd be willing to share?
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Stick
I’m glad she’s ok. That said? I don’t understand the logic behind using a NON-tubeless tire when a tubeless version of the same tire exists - for exactly this reason.

I mean, I get why you did it: You say you want ‘field serviceability’, but... if the tire hadn’t rolled off the rim as the non-tubeless version did here - this post wouldn’t exist and your partner may have continued on without the mess and fuss of a tube install.

Intentionally running a ‘loose-fitting’ bead (“removed easily without tools”) at the lowest possible pressure reads like a great recipe for problems. I.e. Your desire for field-serviceability is a kind of self-fulfilling prophecy, IMO.

If it’s confidence in your equipment you’re after, I’d stick with tires specifically designed for tubeless use.
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ljsmith
I've been riding tubeless for 10 years.  Back then it made sense to run regular tires, because there were so few tubeless options, but now with all the available tubeless tires on the market, I don't see any reason to run regular tires tubeless.  If you use a high quality sealant and carry tire plugs, you probably would never need to get the tire off the rim out on the trail anyway.  I know Stans rims were originally designed to run regular tires tubeless.  However they also offered an "Olympic" rim strip to be used in their rims to do this, so it tells me even they know that running without a rim strip has risks associated with it.  Any time I have ever run a regular tire tubeless on Stans rims I have used these rim strips.  A regular tire just doesn't have a strong enough bead to run tubeless without one.  I know many people have successfully run regular tires on Stans rims, but to me its just not worth the risk.  Basically I am saying to use tubeless tires, or at the very least get some rim strips.
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imwjl
I'm glad everyone is okay.

This seems like the why or classic story to support only using tubeless compatible tires and to know what air pressure is your minimum to avoid pinch flats and burps. In the time I've considered and used tubeless most all the problems I've seen and been aware of have been some form of not following instructions or best practices.
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Stick
Not for nothing... there’s also this... straight from WTB.
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runrideski
Thanks for everybody's responses so far.
We're pretty confident that the crash caused the tire to unseat, and not the other way around.
We just wanted to see if others had similar experiences with (various) tubeless setups, or if this was a rather isolated incident cause by some extreme (but unlikely) lateral leverage at the tire/rim interface.  Anyway, with only a 6" section coming unseated, this incident was nowhere close to rolling the tire off the rim.  And it still took >40 sec for the tire to go fully flat.

Rightly or wrongly, I followed the advice of others on this forum (including one of the moderators) when selecting between the 'race' and TCS (tubeless) versions of this tire to pair with our Stan's Grail rims.

for example:

-"Stan’s specifically recommends NOT using WTB tubeless tires. I’ve been running the Nano 40c race version tubeless on Stan’s Grail rims for a year. It sets up perfectly and have never burped them. Running at 30 and 33 lbs for gravel and moderate single track. My weight 150 lbs. Have several friends with the same setup and equally good results."

-"Mated to any of WTB’s suitable TCS rims, you have the first, and thus far only, “system” for tubeless tires specifically aimed at gravel road riding. What is more, these tires do work on HED Belgium+ rims and Ardennes+ wheels, and likely other tubeless rated rims for road and mountain use. Beware of mating these with Stan’s rims though, as this is not a good fit."

-"I’ve been running the standard (non TCS) Nanos tubeless on Stan’s Alpha 340 rims for several months now with complete reliability and very easy setup. The weight is much more competitive and I am very happy with the performance."

-"...WTB TCS tires do not fit well on Stan’s rims, as Stan’s rims are meant to fit NON TUBELESS TIRES and convert them to tubeless use. (This is why many have been confused with this review, thinking that the Nano 40 does fit Stan’s rims, which is true if you are using the NON TUBELESS Nano 40’s.)"

-"...Stan’s rims interface with the folding bead type Nano 40, (and most other folding bead tires that are NOT TUBELESS), as that is what Stan’s main purpose in design is for."

-"...From the Stan’s tire page, ” Not Recommend Tires. WTB TCS and UST 29 inch tires are too tight for Stan’s Notubes rims"

-"I have tried all three versions of the 700c Nano. If you have Stans rims, go Race or Comp."

-"I use the non-TCS version set up tubeless (TCS Nanos weren't out when I purchased mine). I keep pressures low, under 40psi. I have never had a burp, blowout or even a minor leak and I beat on these things."

Regarding field serviceability, I wasn't looking for a 'no-tire lever' solution with this setup, and I always carry tire levers and spare tubes with me (not CO2 though).  While I can get these tires on/off without levers, it isn't easy to do so.  I think this has more to do with the depth of the rim's 'well' than a loose bead.  It also takes ~35 psi to get them to fully seat, and they snap loudly when they seat.  I use a compressor to go up to about 30psi and finish seating the tires with a floor pump, so i can control the pressure.   

Also, I have only used one 'non-field serviceable' rim/tire combo:  3.8 Surly Nates on LightBicycle carbon rims.  This combo was so tight that others have considered cutting the rim to save the tire or vice versa, as once the tire is seated it is EXTREMELY hard to get off, because the rim's diameter significantly increases between the sidewall and the well.  Anyway, the one time I got a flat on that setup meant a pretty long and unpleasant (hypothermia-inducing) walk through deep snow.  Not particularly interested in a repeat of that experience.





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dangle
I'm glad everybody is mostly okay!

From somebody that races about a half dozen different Stan's rims and has a bit of experience on WTB cross, gravel and mt bike tires.....it basically sounds like a big 'burp' happened. Lateral loading of the tire and low pressure. Typically a burp wouldn't cause a crash though. It sounds like the crash/slide caused the burp (but obviously I wasn't there or riding the bike). You sound very knowledgeable, so maybe you have had the following experience. Say it's a cyclocross race and you're getting some lateral force on your rear tire from turning hard, 'skipping' along a bumpy surface while turning, or on an off-camber and you hear a little air fart out of your rear tire and find some grass pinched between the tire and rim after the race.

Anyhow, it sounds like the combination of low pressure and the 'looser' tire beads from the race version may have been enough for the tire to get pulled back inside the rim and loose the 'seal' to create an air escape (big burp) that either (a) let out enough air for the tire to fail and dump your friend or (b) the unusual direction of the tire's path during the rut-based crash was enough to burp the tire.

I haven't had much issue mounting WTB TCS tires on Stans rims. It's not an easy install, but it's worth it and I can get them off with two levers. WTB and Schwalbe are the only CX tires I have never been able to burp. It could be worth swapping over to the TCS tires when it's time to replace the current ones. 
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runrideski
These are really good insights, thanks!

After one bad experience with WTB tires...side knobs completely ripping off on brand new MTB tires... like 15 years ago, these are the first WTB tires that I have used.  I've more or less stuck to Specialized, Kenda and Maxxis for MTB, plus Clement tires for cyclocross.

The grass pinched between rim and tire is something I've had happen when burping (too low pressure on an extreme off-camber) a non-UST tire mounted tubeless on the back of a UST MTB wheel (Crossmax).

I think this would have happened in this case as well, except that a few small bits of gravel that got pinched between the tire and rim, prevented the tire from snapping back into place (and sealing up, post-burp) against the inner sidewall of the rim.
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dangle
runrideski wrote:
After one bad experience with WTB tires...side knobs completely ripping off on brand new MTB tires... like 15 years ago, these are the first WTB tires that I have used.  I've more or less stuck to Specialized, Kenda and Maxxis for MTB, plus Clement tires for cyclocross.


I think the current WTB stuff is pretty good. The head designer/engineer (I don't know the actual term) from the years Clement was pumping out all sorts of stuff under the Donelly name has been over at WTB for the last year or so too, so hopefully it keeps getting better.

runrideski wrote:
The grass pinched between rim and tire is something I've had happen when burping (too low pressure on an extreme off-camber) a non-UST tire mounted tubeless on the back of a UST MTB wheel (Crossmax). 

I think this would have happened in this case as well, except that a few small bits of gravel that got pinched between the tire and rim, prevented the tire from snapping back into place (and sealing up, post-burp) against the inner sidewall of the rim.


Possibly. Once you have lost that air, it burps easier and easier until you have a sad little tire barely hanging onto the rim too. I still think it was the wrong tire for the pressure and application in your friend's instance.

The 2018 Specialized tires seem to be a tighter bead than before as well. I tested our their newest Terras at a CX practice on Stan's 21 mm ID rims last night about 24-25 front and 26-27 rear with good results. The previous version would have burped in the rear for sure at the same pressures and conditions. The newer Specialized tires could be a good middle ground between being able to fix a flat and not having to worry about burps/loose tire fit. The new Tracer is supposed to have the same updated bead as the new Terra and comes in a 38. They aren't WTB/Schwalbe tight, but should give a good hold.
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