Cycle Inner Tube Dilemma

[dibble1]

I have bought a nice second hand Carrera mountain type with 26" rims, however it is eating inner tubes. It's clear what is happening the tube or a combination of the tube & tyre is actually rotating on the rim, moving the valve at a slowly increasing angle until it ruptures. These ARE the recommended size but there seems to be excess tube when they went on.
I could understand it happening on the back wheel which is subject to torque but on the front too??? Perhaps I don't have enough pressure in, I'm putting in around 40psi. I can't see it being this as I've never seen this before!!
The tube is moving clockwise as the wheel is moving anti-clockwise. Anyone any ideas?

[Jomlett]

Have you also fitted a rim tape?

[dibble1]

Many thanks to you all

[ChillDoubt]

If you're unaccustomed to fixing minor problems yourself, try and avoid Halfords.
You'll get excellent service at your local independent bike shop and probably at half the price too.

[snags]

http://bicycles.stackexchange.com/questions/9929/tube-constantly-getting-punctured-near-the-valve

[joggerjayne]

Are the tubes fat enough? 26" tubes come in different tube diameters.

[joggerjayne]

Maybe the tyre is moving round the rim, and dragging the inner tube with it.

Which, as methyl suggests, would mean a tyre issue, not an inner tube issue.