IBLS Wheel Standard

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Current Version

Drawing courtesy of Bill Donovan of RealTrains.com


1. Each line which joins an arc is tangent to the arc

2. In prototype practice the flange radius (r) is not a simple radius.

3. On 3/4" scale there is a difference in back to back and wheel check between wheels designed to run on 3-1/2 inch gauge track which would be laid to have a flange-way designed for only these wheels and dual gauge track that was 3-1/2 and 4-3/4 gauge laid with 1 inch scale components. On the dual gauge we use a 3/4 inch scale diameter and width wheel with a 1 inch scale flange. Since the track gauge value must remain the same even though the flange is wider it changes the wheel check and back to back dimensions to a smaller value.

IBLS Wheel Standards
Scale TG=Track Gauge T=Tire Width W=Flange Width F=Flange Depth R=Contour Radius r=Flange Radius B=Back to back WG=Wheel Gauge WC=Wheel Check
1/2" (17/32") 2.500 min 9/32 min 0.063 max 0.075 max 0.025 min, 0.033 max 0.030 typ 2-9/32 +0.200 -0.000 2-15/32 +0.000 -0.020 2.405 ref
3/4" 3.500 min 0.406 min 0.094 max 0.094 max 0.047 min, 0.063 max 0.040 typ 3.281 +0.020 -0.000 3.470 +0.000 -0.020 3.375 ref
1" 4.750 min 0.505 min 0.125 max 0.140 max 0.062 min, 0.083 max 0.050 typ 4.437 +0.020 -0.000 4.690 +0.000 -0.020 4.562 ref
1" 5.000 min 0.505 min 0.125 max 0.140 max 0.062 min, 0.083 max 0.050 typ 4.687 +0.020 -0.000 4.940 +0.000 -0.020 4.812 ref
1-1/2" 7.250 min 0.750 min 0.156 max 0.187 max 0.094 min, 0.125 max 0.062 typ 6.870 +0.020 -0.000 7.190 +0.000 -0.020 7.031 ref
1-1/2" 7.500 min 0.750 min 0.156 max 0.187 max 0.094 min, 0.125 max 0.062 typ 7.120 +0.020 -0.000 7.440 +0.000 -0.020 7.281 ref
1.6" 7.500 min 0.750 min 0.156 max 0.187 max 0.094 min, 0.125 max 0.062 typ 7.120 +0.020 -0.000 7.440 +0.000 -0.020 7.281 ref


1. The flange radius (r) is not specified by IBLS but has been calculated from F, W, and R

2. LBSC pointed out that 2-1/2 inch gauge models are actually built to 17/32 inch scale.

3. Nick Edwards recommends minimum wheel width of 0.800 inches for 7-1/4 inch gauge equipment to be operated on dual-gauge track.

See also the 1981 IBLS Wheel Standard.

CAD Drawings

Here are IBLS Wheel Standards for individual gauges and scales. Track owners and clubs adopting IBLS Wheel Standards may include these documents in their handbooks. Many thanks to Bill Donovan of Real Trains Inc.

CAD Files

CAD Files have been created for the various IBLS Wheel Profiles using Autodesk Fusion 360 (which is available for use by hobbyists for free). For example usage see CAD.

Non-Standard Scales

The dimensions presented above were determined by careful consideration of several important factors. The white paper entitled "Determining Wheel and Wheelset Dimensions" lists and describes these considerations in detail. It will help guide modelers of non-standard scales to calculate dimensions for wheels and wheelsets, and is suggested reading for all modelers who design, build or inspect wheels.

From the introduction:

In order to allow inter-operation of equipment on multiple tracks a series of standard dimensions have been developed that apply to the design, production, and inspection of wheels and wheelsets (two wheels and an axle). The information that follows discusses some of the reasons for certain dimensions and provides guidance as to the selection of specific values for all required dimensions.

RMI-25 Specification

The RMI Railworks RMI-25 Specification recommends using a taller flange for 2.5 inch and 3-3/4 inch scale equipment on 7.5 inch and 7.25 inch gauge track.

Wheel Gauges

Profile Tools


by Ken Shattock

In 1974-1975 there was a Blue-Ribbon committee formed of SIX (6) individuals who were asked to meet and put together a defined list of BLS Wheel Standards. These individuals, known to many in our Fraternity, were as follows:

The efforts of this group were published in Live Steam Magazine, October 1974.

The committee members were presented with the "10th Annual Live Steam Magazine Award" on December 1, 1979 by the late William Fitt, then-Editor of Live Steam Magazine.

These "Interim IBLS Standards" have been widely adopted and have become the accepted wheel standards for the hobby.

by Rick Henderson

As worldwide communications improved and it became evident that having two standards for 1:8 scale modeling in the U.S. was counterproductive, an attempt was put forth to adopt a true standard for track gauge, wheel profiles and couplers. The organization known as the International Brotherhood of Live Steamers was formed, with representatives from areas around the world working with riding scale railroads. Via mailings, all known private and club railroads were contacted and asking for input on what the standards should be so a single set could be established. From the replies, it became abundantly apparent there was no easy solution within the U.S. and the I.B.L.S. settled on adopting and recommending standards following those being used in California and sent these out as “proposed standards” to everyone. Since these first included 7-1/2” as the correct gauge for 1:8 scale, they were never officially adopted by everyone and have remained as proposed ever since. However, in the U.S., these proposed standards have been used by most everyone for wheels and couplers and each area has used their local gauge standard. This has allowed for the trains to easily travel to other railroads and interchange equipment fairly easy, except for crossing The 1/4” Demarcation Line in the northeast. Today if you look at most IBLS wheel and coupler charts, you will find gauging standards for both 7-1/4” and 7-1/2” that have become the accepted standards by most.

by Keith Taylor

Posted on Chaski.org, 4 March 2007:

As the last East Coast secretary of the IBLS, and having known Mr. Purinton, the founder of the Brotherhood of Live Steamers, I can tell you he was not opposed to standards. He felt that there was no need to create "new" standards as there was already a published set of standards in existence since the dawn of the Twentieth Century.
The "Live Steam" hobby came to us from England, and live steamers used the standards of the Society of Model and Experimental Engineers. These standards were developed by Henry Greenly, and are still used virtually all over the world....except here.

Dual Gauge Track

From Bill Donovan of RealTrains Inc.:

Many clubs have 3-1/2 inch and 4-3/4 inch dual-gauge tracks (3 rails). These are laid with 1 inch scale rail and frogs. The 4-3/4 inch gauge is for 1 inch scale. The 3-1/2 gauge is for 3/4 inch scale.
To be completely compatible any 3/4 inch scale equipment operating on this track should have flanges built to the 4-3/4 inch gauge standard (but the width can be as in 3-1/2 inch gauge). This is seldom done but the equipment is so small and light it is less of a problem.
For 3/4 inch scale equipment I prefer to use the IBLS 1 inch scale 4-3/4 inch gauge wheel dimensions directly and then modify the three wheelset dimensions B (back to back), WG (wheel gauge), and WC (wheel check) by decreasing the 4-3/4 inch gauge dimensions by 1-1/4 inch, as shown in the table below. You cannot use the 3-1/2 inch gauge wheelset dimensions since the wider flanges from 4-3/4 inch gauge will change the back to back dimension.
Dual Gauge 3-1/2, 4-3/4 Suggestion
Scale TG=Track Gauge T=Tire Width W=Flange Width F=Flange Depth R=Contour Radius r=Flange Radius B=Back to back WG=Wheel Gauge WC=Wheel Check
3/4" Modified 3.500 min 0.505 min 0.125 max 0.140 max 0.062 +-0.010 0.050 typ 3.187 +0.020 -0.000 3.440 +0.000 -0.020 3.312 ref
1" Standard 4.750 min 0.505 min 0.125 max 0.140 max 0.062 +-0.010 0.050 typ 4.437 +0.020 -0.000 4.690 +0.000 -0.020 4.562 ref
In a similar way there are some modelers that follow 1-1/2 inch scale narrow gauge (from 3 foot gauge prototype). They seem to all be in the United States so they run on 4-3/4 inch gauge track. If they have laid new track using 1-1/2 inch scale rail and frogs then the only change needed to the 1-1/2 inch scale standard is to decrease the wheelset dimensions by 2-3/4 inches. If they run on existing 1 inch scale tracks then they need special wheels with 1-1/2 inch scale width but 1 inch scale flanges. Here, the back to back (B) is the same as for 1 inch scale on 4-3/4 inch track.

See also:


The following organizations use, recommend or require the IBLS Wheel Standard.

User Comments

Posted on Chaskit.org by Matt Mason, 17 January 2006:

Whether or not the wheel standards were "formally" adopted, so many clubs in the US (especially western US) use them they have become defacto standards. Yes, some clubs use other dimensions, and you should use what works for you and your club. As mentioned before, just because these dimensions are out there, you can still model however you want. As a testament to these standards, I was able to fly from California to New Jersey Live Steamers with my equipment, put the loco on the track, and run with no derailments. I like a set of standards, myself.


From "About Our Scales":

On February 1st, 1899 a subcommittee of the Society of Model Engineers recommended five standard model railroad gauges (spacing between the rails) numbered 0,1,2,3 and 4.
Society of Model Engineers Gauges
Track Gauge Track Width
0 Gauge 1 1/4 inch
1 Gauge 1 3/4 inch
2 Gauge 2 inch
3 Gauge 2 1/2 inch
4 Gauge 3 inch


  • "BLS Wheel Standards: Detailed Proposal", Live Steam Magazine, Oct 1974
  • "Open Letter to the 'Committe of Five'", William C. Fitt, Concerns addressed to the BLS, Live Steam Magazine, Aug 1975
  • "IBLS Wheel Standard: Back by Popular Request", Chart, Live Steam Magazine, Oct 1981
  • "IBLS Secretary's Report - Western Region - 1-1/2 Scale Standards", Richard Thomas Jr., Live Steam Magazine, Mar-Apr 1998
  • "Mini-Rail Notes - Wheel & Coupler Standards", Lewis Soibelman, Live Steam Magazine, Feb 1991