G scale Thomas back to back needs to be reduced

[MAELLIS]

I need some help. My local club here in Norway has built a layout with Peco gauge 1 track with a minimum radius of about 25 inches. We have an exhibition on Saturday and to-night we found that my G scale Thomas won't run though the curves.  I have found that the track width is about 1mm less than Peco's G scale and LGB. I need to reduce the back to back on Thomas's drivers. Does anyone know how the wheels sets are made up ? Are the wheels just push fitted onto insulated axles ? I was hoping to pull the wheels apart and reduce the length of the inner axles. Anyone else done this ?