Hello All,
I’ve recently started commuting to work. The bicycle I’ve bought is specialised tri-cross elite. It is kitted out a winter bike really.
• Rear rack
• Fenders
• Lights,
• Tool kit, spare inner tube
• Pump
• Water proof detachable pannier
Id actually bought the bike about two months ago and had covered roughly 150 miles (not commuting) prior to me using it for my daily commute. Last week was my first full week.
The other day i decided to put some air in the rear tyre, i tapped the end of the presta valve and proceeded to put some air in, all of a sudden the tyre lost all its pressure, i thought this was somewhat unusual as I hadn’t over pressurised the tyre. When I took the tube out I noticed that it had ruptured where the valve joins the tube (picture attached) I duly replaced the tube with my spare and off I went to work the following morning. Roughly half way through my commute (my commute is roughly 5 miles) the front tyre completely deflated. I tried to pump the tyre back up but i could tell by the way it deflated that it wasn’t going to pump up! So then, as I had used my spare the previous night I had to walk to work 
Upon inspection of the tube it had ruptured in the same place. I put this down to both of them being a cheap inner tube. I had replaced both the burst tubes with continental inner tubes. I thought this problem was short lived, and I even decided to carry two spares to never come up short again!
Today I went out for a spin, and to my despair the rear tyre lost pressure again. This was a continental inner tube, so I had the joy of carrying out a roadside repair in the icy wind and rain. Having now got home and inspected the inner tube it had also failed in the same place. There definitely seems to be a recurring problem. And I don’t think it’s a batch a faulty inner tubes
That’s the outline of the problem. The tubes that the bike came with, the valves didn’t have a lock nut on. When I replaced the first burst I assumed that the lock nut had to go on the inside of the bicycle rim. And this is firstly something i wanted to check, is this correct place for it?
I’m intrigued to hear if anyone else had had this problem with inner tubes failing at this point and if so what is the root cause of the problem?
Any feedback would be gratefully received

Carlos

you're putting the locknut inside the rim, as in between the inner tube and the inside of the rim? If so that is wrong, the locknut goes outside of the rim and screws down against it. It doesn't need to be screwed on tight, just enough so that the nut contacts the rim.

it's screwed up against the rim outside the tyre, I probably wasn't being very clear!

If you're able to install and pump up Presta tubes without a locknut, then don't bother including locknuts in the future. Is the valve stem crooked at all when you're done?

Is the rim drilled for Presta or Schraeder?

Never tighten the lock nut.

Lock nuts are optional.
Any rough surfaces inside the rim near the hole for the valve?
Whether the hole is for presta or schrader is a good question. (above)

I had this happen when I first got a bike with Presta valves. Went through several tubes, never having a puncture flat but always tearing at the valve. I finally realized it was my cheapo floor pump. The head was too tight and hard to get on and off (mostly the OFF, I suspect) the valve apparently to the point of weakening the junction. Can't remember which brand but it was likely whatever was cheapest at REI. Got a decent pump on sale, no more issues.

Also, I assume your tubes are of the correct size range?