Adding a traction tire to an MTH trolley

[cruikshank]

 We just got an MTH trolley for our layout. It's the Bump and Go type. It seems like a pretty nice trolley, but our trolley line has some grades just like the prototype. The Lionel-ville were able to make the grade because they have a traction tire. There is no groove, can we use a traction tire, a small orthodontic rubber band or even that rubber coating that you dip tool handles into. Something to give it a little more grip. Any ideas?  Thanks,  Dave