Track and wheel standards

The NMRA Fine:HO standards allow for the use of RP25/88 wheels with a flangeway of 1mm.

The standards also allow RP25/110 wheels to operate successfully.

The full S3.1 and S4.1 standards are available on the NMRA website, but the basic dimensions for Fine:HO are shown in the diagrams below. All values shown are the minimum required.  The standards specify both minimum and maximum values allowable.

All dimensions are in millimetres.


Track gauge (G) = 16.5

Check gauge (C) = 15.6

Flangeway (F) = 1.0


Wheel check gauge (K) = 15.6 max.

Wheel width (N) = 2.2

Flange width (T) = 0.6 max.

Flange depth (D) = 0.6 max.

Below is a one page PDF showing excerpts from the NMRA Standards.


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