Larry posts this question to readers:

“I recently set my pre-1980s N-gauge train up after it was in a box for fifty-some years. I set up a temporary oval track with no switches and was absolutely amazed and excited that it still works. Now I am working on a permanent layout and purchased some new track pieces including manual switches, all code 80 which matches my old track. My problem is derailments at the switches and I believe the cause, thanks to the tips here, to be the old wheels on my locomotives and rolling stock. I shopped around online to buy new wheels and quickly got lost. My first question is if RP27 the correct standard or should it be RP25? My second question is how can you tell for sure if you are buying wheels made to the correct standard? I see lots of wheels for sale from multiple manufacturers but they don’t have details on specifications. I have all old style couplers as well but am hoping to get away with just replacing the wheels. Thanks in advance for any and all help!