What you have there is a typical low-friction design using pointy axles riding in metal cups. Or at least I hope the axles have pointy ends. You can't get any better that that (and still have electric pickup. Kato passenger car trucks use this type of design and they roll very freely.
I'm really surprised that these do not roll very freely. Maybe the axles are too wide and they press hard into the bearing cups? Or maybe there is another point of friction in there? When you hold the model upside down and flick the wheels don't they spin for quite some time? They should. Maybe when the model is on the track the flanges rub against the floor?
Absolutely no direct experience with these cars, but have refurbed a couple hundred older cars for rollability and have found problems vary:
1. Distortion of metal wipers; in or out; also lateral displacement and often only on one side of truck.
2. Distortion of truck frames themselves causing greater friction by narrowing axle movements.
3. Gunk in them, simple. Clean with a needle point file, use a sharpish lead pencil to add lubricated surface. Same often on axle points themselves.
4. Out of gauge or out of camber wheels/ set. Wheels with loosened insulators that are slowly twisting out of true can be difficult to spot. IIRC I used the flat of an Xacto blade to 're-press' them flat while on the axle. If they moved at all I generally learnt to throw them away (i.e. become scenery fodder). Invariably they would not perform correctly no matter the 'fix'.
5. Slightly retapering needle point tip on axles with a good swiss flat file (old school- not the rubbish cheap things these days).
6. May be out of era, but Atlas make a Caboose truck that will take a new wheelset.
Having said that last bit, I'll repeat that the most cost -effective refurbs I have used Atlas steel wheels (both older and recent) on
all manner of vintage cars of 70-80's N scale that you cant find in modern manufacture. For example older Atlas/ Roco/ other 'OEM'
40'-ish emergency war gons, I'm using to represent narrow gauge cars.
Trust these may help, regards
Dave
