This seems to be a recurring MTB problem I put up with as just ‘one of those things’, yet it has occurred to me that maybe I’m the only one affected by this affliction… 😯

Every once in a while I seem to completely trash an innertube, generally in dry dusty conditions, as heavy braking – particularly on the front – seems to cause the tyre to rotate round the rim slightly, taking the innertube with it and eventually severing the valve.

This can be quite exciting at times, as the front tyre will have a propensity to go off with a bang and a whooosh, just at a critical point while pinning it through fast rocky tech sections. I like to think that events like this help keep me razor sharp and rad.

I expect that it won’t be too long before someone comes along with a helpful comment like ‘Tubeless!’ or something like that, but I was hoping that maybe there’s been something I’ve been missing in my conventional tubed setup all along that would overcome such issues. Velcro, maybe? Or carpet grip?

Perhaps I just need to brake less and be less sick generally.

Talcum powder the tube. This lubricates the tyre to rotate on the rim should it need to without pulling the inner around with it shearing the valve stem.*

EDIT* Now that may be urban myth – according to Jobst Brant it is http://www.sheldonbrown.com/brandt/talcum.html and he’s knows a fair bit of stuff. Although I think his article specifically relates to thorn punctures, not stem tears – even though he covers friction between inner and tyre. But Ive found it to be the cure when I suffered a spate of torn valve stems.

what kind of pressures are you running at?

How old are the tyres? It generally happens when the bead is starting to get a bit baggy.

Ooooo pressures… Ummmmm…. 35 – 40psi I think. Firm to the touch, but not too firm, with a little bit of give, if that makes sense. Sometimes quite old tyres, sometimes quite new. It doesn’t seem to make much difference!

I reckon you might be on to something with that talc thing though, and sheldon / brandt is talking tatwaffle. Thinking about it, I’ve had to prise my inner away from the outer on other occasions, because the two have become fused. Hmmmm..

Check there are no sharp edges round the hole in the rim, I had this problem on a road bike, and a quick sand with some wet and dry sorted it out.

I had the same problem for ages.

Velox rim tape and a bit more wind in the tubes helped

After the same thing happened to me three times on one ride I converted to getto tubeless.Problem solved.

It has happened since I put talcum powder in…..

touch woood

Not wanting to cast aspersions, but…

Panaracer tubes perhaps?

I had a shed load of them happen a few years ago, always going at the valve stem join- changed to michelin and conti tubes, never happened again! But as mentioned, Baby Powder!

What tyres and what rims are you running? Or have I missed that bit?

Some rims are slightly smaller than others. Some by design (e.g. Stans) and some just by manufacturing tolerances. Same for tyres. Some will be looser than others. I’ve found Bontrager rims and also their tyres be especially tight.

Just curious, are you sure of the pressures? Only time I have known for tyres to slip has been when the pressure has been low. Basically the tyre is moving in relation to the rim but the tube is held by the valve.

is it worth running Presta tubes? I’m speculating here but maybe the lockring will help reduce the force on the valve stem.

I had an experience years ago when I kept ripping valve stems. Changing from a mini pump to to a floor standing track pump sorted it. The mini pump was stressing the valve because it was directly attached whereas the track pump uses a hose, and any movement from you pumping is prevented from moving the valve.

I used to suffer with this, and in the end I binned the tyre and the problem went away.

I think it happens more when the bead gets sloppy

I went tubeless and it cured it straightaway!. If you insist on running tubes, Schwalbe use steel valve stems with lockrings on both types of valve.

Hmmm… some interesting ideas. I’m definitely sure this has happened with pretty much any combination of old / new tyre rim I can think of. Like I said, maybe it’s because of my rad skilz and that I brake like an animal 😛

If anything my tyres are likely to be inflated more than 40psi, because I just can’t stand sqidgy tyres.

Currently running a selection of 2.1 – 2.25:

Shwalbe RR
Shwalbe NN
Michelin XC
IRC Mythos XC II
Bontrager Mud X

On rims by:

WTB
Mavic

and presta tubes, which are:

Quite cheap

So maybe that’s the problem. Or maybe I just need to have wheels that smell like a baby’s bum..

This happened to me a lot with Panaracer Fire XC Pro tyres – front wheel, after I’d had the tyres a couple of years. As far as I could make out, the bead was slipping round the wheel under braking, ripping the valve off the inner tube. I tried various inner tubes, with the same result (although some brand-name ones resisted it better than others); I talced the inside of the tyre with some impact at first; I even tried reinforcing the valve/ inner join.

Eventually I gave up and bought new tyres and haven’t had a problem since. I figured life’s too short to be worrying about it every ride, and I have better things to do with my cash than spend it on brand new inner tubes every couple of weeks!

extra run or 2 of rim tape to increase effective diameter? – might increase friction too if it’s cloth type

Only ever happened to me using Panaracer tyres.

Same here with Panaracers . I use talc when running tubes .
There was another fix wich involved dabbing super glue around the bead socket on the rim . Allow it to fully cure before fitting the tyre , the added resistance of the dried blobs of glue stop the tyre rotating .
alledgedly

If you are using lockrings, don’t lockring down to the rim, instead use the lockring to lock the valve cap on.

I suffered from a spate of this with Michelin XC Dry 2 tyres on Mavic 717 rims, especially on long, fast descents in Greek mountains. Maybe the high ambient temperatures aggravated things?
I didn’t relish the prospect of being dumped off at speed(I’d been lucky up to then) so I converted to ghetto tubeless.

This happened to me four times in one ride, with new wheels, tyres and tubes. We ran out of spare tubes, and ended up walking 🙁

I ditched the Prestas, and reverted to Schraeders, and haven’t had a problem since

I have had them move but never disasterously in 1 ride. I just let them down, tug the tyre round until the valve is straight and inflate. 2 minute jib when you are checking the bike over.

Happened to me a few years ago with a set of panaracer cinders that had gone baggy around the bead, was going through at least 1 tube a ride for until I changed tyres, not had a problem since then.