Traction Tires on curved grades

I'd suggest concentrating on making the curve as wide as possible and the grade as shallow as possible.  The forces will be maximized on the out side of the curve.  

Traction tires are usually paired.  On a steam engine on one axle, on a diesel on one side of one truck and the opposite side on the other.  Unless you plan to run in one direction only (aka clockwise or counterclockwise) the wear and tear should balance out.  

I suspect you might get a slight boost in performance if the traction tire side was on the outside.  You will also get additional wear on that side as the forces will be concentrated there.  Changing tires is not much fun and I'd really consider ways to keep that to a minimum.

Traction tires seem to be subject to heat and longevity deterioration. I've purchased a couple of very good older Weaver steam locomotives that were never out of the box. Manufactured in the early 90's the tires fell off almost instantly.  Replacement was not so bad.    

In direct answer to your question: yes, it does, but it is only a slight difference and other things tend to be more important.  All other things being equal, generally it is slightly better if the traction tire is on the outside.  I experimented on this with some one-traction tire BEEPs years ago and if you set up a test track I could see the difference.  But it is not a big difference and other things often aren't equal.  

What matters much more is if the traction tire is on the downside of any slope across the track (i.e., on the lower side if the track is not level side to side): many model railroaders bank their curves very slightly, which tends to make the loco lean to the inside, putting more weight on that inner loop: if the traction tire is on that side with more weight on it - that matters.  

This matters a lot more with 'Streets vehicles (which mostly have one traction tire only) than with locos, probably because 'Streets vehicles don't have a lot of weight to push down for traction and also because they go around curves as tight as radius = 8.5 inches.  The way I lay out all my 'streets roads, and run my vehicles, they turn left much more than right, so when I assemble them I put the traction tire on the right side.  

The very long depressed-center flat trailer truck I posted yesterday is one of the few examples where this matters: it has to go around eight left turn curve sections and two rights to orbit my country road loop.  It has a traction tire only on the right side of the drive axle: it goes through all the left handers well, but spins its wheels on the right had curves.  (This will not be a problem when done because it will have an extra 4 oz of weight over the drive axle for additional traction.)

Thanks, Chuck, Mike, and Lee, for all the usful information. The bit about the banking of curves is especialy helpful as I plan to use some banked AF ogauge track on my layout and perhapes reducing the banking with shims can balance out some of the discrepencies in two way travel on those curved grades.

The Steam engines that I will use on this portable layout are from lionel starter sets and have only one traction tire, (They are also quite heavy), but will negociate 027 curves, which will be part of this pike as well, but not on any grades!

You might consider Frog Snot, which if you are not familiar with it , is a real product, a rubbery paint that you brush on the traction area of a driver and it simulates a traction tire.  You lose some of the electrical connectivity that way and so you have to be a bit judicious in its use (put it on two many wheels and you lose all power), but applied to the opposite wheel on an RTR loco with only one traction tire, it often helps a lot.  Good thing is that if you don't like the result, you can scrape it off with a good X-Acto knife and are back where you started with no harm done.

I've heard of it and it sounds like it would help.

Thanks!