Traction tires for 4-6-0

[nymark]

My Dad left me a good number of N scale engines. Two of them are Bachmann 4-6-0's with dual mode decoders. Neither had been run in a number of years if at all and both ran pretty well when I programmed them with my NCE system. Unfortunately the traction tires fell off. They still ran "okay" but I want to replace the traction tires and am thinking of buying the whole wheel assembly. I think it's just a matter of taking the bottom from the chassis and swapping them out and plan on taking one apart tomorrow to see if I am right. Can anyone give me advice about this problem before I dig in. Any insight would be much appreciated! Phil Nymark