I noticed that my rear tire was flat in my garage the other morning. I removed the tube to find that where the valve stem "joins" the tube, was a small tiny tear thus rendering it unrepairable.

How did this happen and is this a common failure in tubes? The tube is a MSR Heavy Duty Tube and it has been in the tire without any incidents since last summer.

 

Do you have rim locks fitted?
Sometimes the tyre can spin on the rim causing problems where the stem joins the tube.
A similar thing happened to me with a heavy duty tube.
A few weeks back I fiited a new tyre.
When I went to pick it up the tyre guy had the stem in one hand and the tube in the other.
He said they just fell apartand all he did was pull the tyre off in the usual way.
I just looked like the rubber had disintegrated.
Anyway, he replaced it at no cost given I have bought at least 6 tyres from him in the last 2 years.

 

easy fix when you replace it do not tighten the valve nut up leave it loose under the cap

 

I spun a tire on the rim and got stranded too. I personally think everyone should run a rim lock. Either that or run very high tire pressure.

Mike

 

The same thing happened to me 2 weeks ago. I was out on an easy ride, running 18 psi in the rear, and suddenly got a flat. I was running a Kenda Tuff Tube, and the valve stem started to separate from the tube. The valve stem wasn't canted in the rim like the rim spun inside the tire or anything like that (I left the valve stem nut loose). It just started coming apart. I squirted some Slime in it and that got me home.

I've since started running a Bridgestone Ultra-Heavy Duty tube and a rim lock.

 

I was riding in a really rocky area, with 18psi, I thought that would be a high enough pressure but I guess not. I rode almost 20 miles back on a flat rear tire. When I got back of course the valve stem was gone. I have to say that Pirelli MT-21 is one tough tire it survived with no damage. I since have gone to a heavy duty tube and a rim lock. I have noticed however that the rim lock throws the wheel slightly out of balance.

 

Rim locks will do the trick, but personally I ride with max air. I've never had a problem.

 

The problem with too much air is that it makes the tire bounce around like a basketball. You'll get much better traction if you lower it down, the exception may be sand, not sure if air pressure makes a big difference there. But I rarely run more than 12-14 psi off-road. I use Bridgestone Ultra-Heavy Duty tubes and two opposing rim-locks, keeps the tire from slipping and balances the tire so no vibes at higher speeds. Also keep the valve stem nut tight up against the valve cap, not down against the rim.

 

Thanks guys for all your inputs.

No I do not have a rim lock. Are they really necessary?

The ironic thing is, the only legal dirtbike trail around here opens up in May and close in October so the bike has only seen street duties since last October....meaning I have had 25 psi in the rear when this failure occured.

The tube that failed was a H/D MSR tube. Should I get another brand and should I go Super H/D?

Maverick, do you mean the 12mm nut on the outside of the rim? Does that help and how loose do you keep it? Would that not cause a whole new set of problems?

 

Brian, Maverick suggested this too. Is this a good practice? BTW, I have metal valve stems on my Ducati(tubeless). How tight should that one be?