You would have to get an Alko axle of correct width but surely not worth the effort is it? I'd just stay with 10inch wheels. Get some new tyres if current ones are more than 5yrs old & leave it at that.
Cabanon TT used an alko hitch,but I always thought the chassis was Conway's own. Good tyres,balanced and at the right pressure will easily cope with continental towing speeds,the Autow website has a section on correct pressure for various weights and speeds.Besides,bigger diameter wheels may make it difficult to peg down
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You won't find an axle to suit your Cabanon. Your axle is designed for central dished rims only. Even if you do find a wheel that will fit and not foul the wheel arches you will increase the height of the unit when set up so you may have to drill holes in the cabin frame to allow for the extra height.