having just finished the building of the first stages of an old analogue layout it was time to try and resusitate the locos. My old DA 800 had plastic traction tyres and would not climb my inclines. Having decided to put on the later rubber tyre i was quite suprised with the result. It climbed the incline pulling 3 coaches with no problem at all. i have an old 3021 which has the same problem so I hope the same remedy will work. A word of warning, to easily change the tyres on the DA 800 I had to undo the valve gear. It was suprisingly difficult to get it together again as it will only fit one way without locking the wheels. I am really glad I decided to do one side at a time so I could compare the other side on reassembly.
It is amazing what you forget, I had not serviced a loco for some years and was really glad I had an old copy of the service manual 0733.
regards

Also have an old one with plastics tires, a brown CE800... Those stiff original tires do not help very much regarding traction...

the only benfet you get with plastic tyres they don't expand (unless you abuse your loco with heavy loads).
By cleaning them and taking the oil or grease of them, does increase their traction.
good suggestion with the valve gears.
One could spend hours trying to work out how do they fit back on again.

John