Tyre noise or something else?

My jim is on 215/75/15 BFG MUD Terrains which haven't got a huge amount of mileage on them. In the last couple of months the front offside tyre has got seriously noisy- before this they were all very quiet.

Pressure is fine, no damage to see and no whee wobble suggesting the wheel is buckled etc. Just a loud thump thump noise- increases more with speed.

I popped it to the garage as it had been suggested the whee bearing was the culprit but he seemed to think it was ok- not v noisy when you spin the wheel and no wobble noted.

Any other suggestions as to what it can be?

vacuum free wheel hub not disengaging?
lubrication missing from inside hub/drive shaft?
(rethreaded) tyre coming loose from the stem of the tyre?

I do remember a school teacher when i grew up in the eighties who had similar trouble with his beetle.
Some of us kids had put pebbles inside the hub caps

Thanks matey- it's on manual hubs. Not sure you mean about the tyre coming loose from the stem of the tyre?

I'll try and swap the spare with the wheel later and see if that helps

Sorry for language problems (I am Norwegian )

The mould of the tyre can sometimes come loose from the stem of the tyre. The tyre can delaminate so to say.. not sure if offroading with low pressure can increase the risk of this happening, but i have had the problem myself with firestone mud tyres some 20 years ago. The dealer said it happens more often with remoulds.
balancing problems can be caused by this .

Ah that's handy thanks- will try swapping the wheels and see if that helps

So the wheel swap has cured the noise!!

Question is what on earth could be wrong with the tyre? It looks fine- no visual damage other than slightly perished near the bead. Nothing stuck in it etc