...my product of choice for most of my rolling stock. I try to replace all plastic wheels with metal ones because the metal ones work as they roll to clean the track, just like the real ones.
A short circuit that showed up recently had me momentarily baffled until my alter ego, CAPTAIN OBVIOUS came to the rescue. One of the last cars I converted was an older Athearn 50' reefer with its original metal sprung trucks. When I lifted the car off the track, all my power was back.
NOTE TO SELF: When installing metal wheelsets, get into the habit of checking the insulated side of the axles to make sure they are all on the same side of the car. That way, self is not inadvertently creating a short circuit through the metal truck...duh. Bonus points are gained by making sure both trucks are insulated on the same side in metal framed kits.
NOTE TO NEWCOMERS: The insulated side is the one done in a non-conductive plastic, usually black. --->Can you believe they used paper or varnish not too long ago? The varnish breaking down over the years is the more likely reason Grandpa's old trains aren't working for some right now...that creates a dead short, leaving folks to believe that the motor is toasted.