NMRA S-4.1 Proto48 Wheel Standards | Modeling the Reading in Proto48

The following is a chart of the different manufactures wheels, wheelsets and trucks that I have had the chance to measure. This does not mean that all of a manufacture’s product as listed here is either in or out of NMRA specification. It just means the products I had the chance to measure were as written below.

Numbers in Black Type are within the NMRA Standards.
Numbers in Red Type are NOT WITHIN NMRA Standards.

Last Updated 01/26/2023

Manufacturer	K	B	N	T	D
Range	1.124 1.134	1.100 1.112	0.115 0.120	0.024 0.028	0.022 0.026
PROTOCRAFT
40/50 ton Dalman Two-Level Truck	1.130	1.105	0.115	0.025	0.024
50 ton Andrews Truck	1.125	1.103	0.115	0.025	0.025
50 ton Bettendorf Truck	1.130	1.105	0.116	0.026	0.026
50 ton ASF A-3 Ride Control Solid Bearing	1.129	1.104	0.116	0.026	0.023
50 ton Barber S-2 Solid Bearing	1.133	1.103	0.115	0.026	0.024
50 ton National B-1	1.125	1.106	0.116	0.025	0.023
50-ton coil-elliptic freight truck	1.132	1.108	0.115	0.026	0.026
70 ton ASF A-3 Ride Control 5’8″ wb	1.130	1.109	0.116	0.026	0.025
70 ton Barber S-2 Roller Bearing	1.127	1.105	0.115	0.026	0.025
Commonwealth 4 Wheel Passenger	1.133	1.110	0.116	0.027	0.025
General Casting Corp’s 41-N	1.132	1.108	0.115	0.024	0.022
Pullman 2410	1.134	1.104	0.115	0.028	0.025
33″ Rib-Back Wheelset	1.134	1.108	0.115	0.025	0.026
33″ 50 ton ARA “D” rated axle	1.129	1.106	0.115	0.025	0.024
40″ Diesel Locomotive Wheels	–	–	0.116	0.026	0.025
40″ Proto48 Geared Wheels for P&D/Weaver Drive	1.134	1.108	0.116	0.026	0.025
NORTH WEST SHORT LINE
#2670-6 Proto48 Geared Wheels for Atlas-O EMD F3’s, GP9 and GP38	1.130	1.106	0.116	0.026	0.025
#2533-6 Proto48 Geared Wheels for Atlas-O EMD SW8/9	1.128	1.110	0.115	0.024	0.024
#2506-6 Proto48 Geared Wheels for Weaver ALCo RS-3	1.134	1.107	0.115	0.027	0.025
40″ Diesel Locomotive Wheels	–	–	0.115	0.026	0.026
33″ Freight Wheel Sets	1.132	1.109	0.115	0.026	0.026
TANGENT SCALE MODELS
50 ton Spring Plank Truck	1.134	1.110	0.118	0.027	0.026
SAN JUAN CAR COMPANY
33″ 50-ton Plastic Wheelsets	1.124	1.100	0.118	0.033	0.026
RY MODELS (Out of Production)
40 ton Fox Truck	1.134	1.109	0.115	0.028	0.024
50 ton Andrews L Section Truck	1.132	1.106	0.115	0.025	0.024
50 ton T-Section Bettendorf Truck	1.134	1.110	0.115	0.028	0.025
50 ton Bettendorf Truck	1.133	1.109	0.116	0.026	0.023
50 ton Bettendorf Caboose Truck	1.134	1.109	0.115	0.026	0.023
50 ton National B-1 Truck	1.133	1.101	0.116	0.025	0.023
50 ton PRR 2D-F8 Truck	1.131	1.110	0.115	0.027	0.025
50 ton PRR 2D-F12 Truck	1.130	1.100	0.115	0.027	0.024
50 ton Vulcan Truck	1.127	1.103	0.115	0.026	0.024
70 ton Bettendorf Truck	1.125	1.100	0.115	0.026	0.023
70 ton PRR 2E-F2 Crown Truck	1.132	1.103	0.115	0.027	0.023
70 ton Keystone Truck	1.132	1.104	0.115	0.026	0.023
100 ton PRR 2F-F2 Truck	1.134	1.107	0.115	0.025	0.023
OVERLAND MODELS INC. (Out of Production)
Diesel Conversion Wheelsets	1.134	1.109	0.115	0.027	0.024
GRANT LINE (Out of Production)
33″ Rib-Back Wheel Sets	1.133	1.105	0.112	0.026	0.024