My tube stems keep falling off

[TexasDualler 32]

3rd time in 4 rides. It's starting to get really annoying. Any suggestions on how to keep from ripping the valve stem out? 2 times it was a ultra heavy duty tube, the 3rd a regular. I powder them pretty good when installing and make sure the stem is perfectly straight in before setting the bead. Rim lock is plenty tight too. Tried going higher tire pressure last time but still ripped out. It's the rear tube by the way. Maybe I need to start using tube grease?

[Bp619 104]

Wow weird never seen that more than once. Time for mousse or tubliss. My preference mousse front to smash into rocks no pinch flats and tubliss rear for traction

[Bp619 104]

Mark tire and wheel with a grease pen see if its slipping. I remember reading about alot of people having issue with trials and especially mitoz mountain hybrid still slipping and ripping stems with rim locks

[TexasDualler 32]

I was thinking about going to mousse actually. I was also thinking it might be the tire. It didn't start doing this until I installed the new desert version AT81. Maybe I'm getting too much traction? Or maybe my rim lock is worn out and not gripping as well as it used to. 

[Oracle 195]

Well, as you have already deduced, the tire is slipping. What tire pressure are you running. Maybe try a new rim lock? If 14 PSI and a good rim lock doesn't work, I'd say there is something wrong with the tire.

[Bagstr 287]

  Would suggest Rim Lock is wrong size.  Even tho tight, no pressure on bead.

[PastaPilot 17]

It hasn't been mentioned but be sure to be using the same size tube for your size tire. I had a 90/100 front tire that I couldn't find a proper tube for and after 3 torn valve stems I put it on the shelf.