I bought some passenger coaches that said they were good for 18-inch radius HO curves. I thought I was good. When they couldn't handle a curve, I got out my Ribbon Rail gauge and measured it. I ended up ripping up the whole curve because it failed the test. Tht was it.
It takes an iron man to play with a toy iron horse.
I have 13 of the original supercontinental line cars and they have been a lot of work. First, as Crandell suggested check the coupler swing, a binding coupler can cause issues as you describe.
Next, flip the car over and make sure one of those underside detail parts has not come unglued and is preventing the truck from rotating all the way. This has been an issue for me.
You can also try backing the bolster screw that holds the truck on, off a smidge, or tighten it up if it has come loose.
Turn the car over, take a pic and post it so we can have a look.
Brent
"All of the world's problems are the result of the difference between how we think and how the world works."
The gauge is a great reference point tool and a great way to realize...well...reality. But, sometimes it doesn't hurt to fudge things a half-millimeter or less one way or the other to see what happens....literally....to try it out.
If I had to guess, though, assuming you have it all straight, it must be that one or both trucks need some sleuthing. Maybe one or both need more azimuthal clearance, and since they can't swing as much as the designers intended, the wheel flanges, faithfully in gauge, still make pretty draggy contact with the inside surfaces of the outer and inner rails along this one curve.
Could be a detail, flashing somewhere, even grit inside the bearing cones of the trucks that prevent the axles from sliding fully.
Even the couplers...they need evaluating to see if they have the same free swing as the couplers on the unaffected cars. Same angle, side-to-side.
Does this happen on a curve? If so what is the radius?
BFlakThe wheels appear to be in gauge and the track appears to be in gauge
Maybe it's just your choice of words, but "appears" is not the same as are in gauge. Unless there is ballast glued to the inside of the rail, out of gauge is the most likely possibility
Henry
COB Potomac & Northern
Shenandoah Valley
One of my Rapido mid train dome cars from the original Canadian set is binding in two areas of my layout. The wheels appear to be in gauge and the track appears to be in gauge as well. Other Rapido cars cruise thru these sections with no difficulty. Any suggestions as to what the problem may be? Any help greatly appreciated.