MTH 2 rail scale wheels

Well, they run on Fastrack, after a fashion - they fit the gauge and the loco will stay on straight sections okay - at least that's my experience, but they do not stay planted well over switches or through curves.  I tried it just to see and it was uglly.  

Generally, scale wheels can hold only on a much wider radius than standard O027 type wheels- roughly 2x as a rough rule of thumb.  So, presumably a loco that will do 36" radius 2-rail would make it through 72" diameter Fastrack, maybe - I wouldn't count on it.  

I have a boxcar I converted to scale wheels just to see.  Even it won't stay on Fastrack well.  

The basic simple rule depends on the kind of track are you using: 2 rail scale wheeled locos are designed for 2 rail track. Hi-Rail wheels are designed for all of the various 3 rail track options. If you have 3 rail track and switches your best bet is to change out the wheelsets to the Hi-Rail wheels.

Now it is possible to run scale wheeled locos on some types of 3 rail track such as Gargraves. I have done so with a great level of success. However, my track had wide radii curves and had no switches.  I ran AC power from my TIU to each of the outside rails of the 3 rail track and DCS performed flawlessly with the locos set to 2 rail...pretty cool IMHO.

Hope this helps answer your question.

The problem will definitely be at the switches due do the much smaller (scale size) flange going thru the 3-Rail switch frogs. I have all Atlas-O, solid nickel silver track, and run quite a bit of 2-Rail rolling stock equipped with 2-Rail wheels, and occasionally have derailments when shoving backwards thru switches. My buddy, SOO NUT, has modified all his Atlas-O switches by adding about .015" styrene shims on TOP of all the guard rails at the switch frogs. I plan on doing the same thing to some of my yard switches, so that I can run more 2-Rail rolling stock.

However, in the long run, you would be MUCH better off to just convert your MTH 2-Rail, fixed pilot, diesel units, to Hi-Rail wheel sets.

Thanks guys, It is what I thought but always good to get others opinions.