Author: Alain LM I recently experienced a weird short on my club layout, which, after a long investigation, was attributed to a brand new Fox Valley Models (FVM) boxcar where one of the axles was fully conducting; of course this is not supposed to happen as their wheelsets are fully insulated, but s... happens even after quality control. Anyway, I had to replace the said axle, and there began my chemin de croix (French for "way of the cross" or laborious exploration) to figure out just how to do this. How do I know the proper axle for that car? Car manufacturers are absolutely silent about it and even FVM (as both a car and wheelset manufacturer) does not indicate which wheelset to use for its cars. So, I had to conduct my own investigations, which I'm sharing with you below. I hope that you will find this useful. Wheelsets are available in a variety of diameter and axle lengths; of course both are important when you want to replace a wheelset. The most frustrating is the axle length as this can make a difference in the truck, though such differences are really minor (you'll need a caliper). So here is the summary of what I've found from various sources: By length (non exhaustive): 0.540 inch: Micro Trains; Athearn; FVM 0.553 inch: InterMountain; some Atlas 0.563 inch: Con-Cor; some Atlas; Bachmann; Kato 0.573 inch: Arnold-Rapido By brand: Information courtesy of Streamlined Backshop Arnold-Rapido - 0.573 in Athearn - 0.540 in Atlas - 0.540 in, 0.553 in, 0.563 in Bachmann - 0.560 in BMLA - 0.540 in Con-Cor - 0.563 in Deluxe Innovations - 0.553 in Exactrail - 0.540 in Fox Valley Models- 0.540 in Intermountain - 0.553 in Kato - 0.563 in Lima - 0.549 in Micro-Trains - 0.540 in Model Power - 0.567 in Rapido passenger - 0.526 in Rivarossi - 0.549 in Roundhouse - 0.549 in Tangent - 0.537 in Walthers - 0.545 in If you'd like more information about wheels dimensions, please refer to this NMRA RP25 standard. Here is a link to the N scale wheelsets featured on TroveStar. About the Author Alain is an avid n-scale modeler who collects North American rolling stock with a focus on Canadian railroads and BNSF and all its predecessors. He occasionally purchases other models from European railroads. He has been using DCC since it's been available and successfully mixes North American and European DCC equipment. Alain regularly contributes to the TroveStar N Scale Model Trains Database (data and blogs), as well as to JMRI. By day, Alain works for a world-class railway signaling firm as an automation and real-time industrial computing engineer. This Frenchman lives near Paris.