Under no circumstances should hot work be carried out on any wheel to which a tyre is fitted. Hot work is any process that generates flames, sparks or heat. It includes welding, cutting, grinding and sawing and particularly the application of heat to free rusted on bolts etc.
When a wheel rim or other steel part of a vehicle wheel is subjected to heat, there is a risk that any tyre (inflated or deflated) attached to it will explode. This can be caused by ignition of the vapours in the tyre, or from degrading of the rubber or lubricating oils. Explosions can even occur later during re-inflation because of the additional oxygen available and the reduction in temperature at which ignition occurs (because of higher pressures).
The inflation of tyres with nitrogen does not make hot work on wheels safe. The tyre can become partially pressurised with air because of inadequate purging at the start of inflation or because air is used to top up pressure.
There have been a number of fatal accidents where heat has been applied to wheels where the tyre was still attached. It is particularly hazardous with large wheels.
Both of the following You Tube videos shows a weld on a large wheel being undertaken in controlled conditions and shows the build up of temperature and pressure within the tyre and the resulting consequences.
Both of the following You Tube videos shows welding on large wheels being undertaken in controlled conditions. The monitors show the build up of temperature and pressure within the tyre and the devastating consequences of the tyre explosion and/or wheel disintegration.