I had this dilemma myself, but upon reading articles on gearsets, where it
is not advisable not to have the same materials meshing with each other,
because you get greater friction, then I did some tests to find out which
type of wheel had the least rolling resistance. I realise the tests were not
very scientific but firstly they put another nail in the coffin for plastic
wheels as when a wagon was released on an incline with plastic and then N/S
wheels, the N/S wheeled wagon rolled on average at least 25% more, the track
being used was Peco N/S. At the time I did not have any vehicles with brass
wheels so could not do any comparative tests to see if they provide any
advantage, but subsequently I came to possess a coach which had brass
wheels. I repeated the rolling resistance tests with a similar coach fitted
with N/S wheels and the brass wheeled coach did fare a bit better but was
not conclusive enough to make me standardise on any future rewheeling to
Going back to gearsets articles, then if you fit N/S wheels on a loco and
have N/S track then there should be increased friction between the two which
should lead to less wheelslip but unfortunately you will use more power to
move the train.
I don't think the wheels were the deciding variable in your rolling
tests. The bearings would be what matters.
Why would you use more power? Less wheelslip would mean less wasted
energy --> less power.
The bearings were not altered but if I had put in "Top Hats" then I would
expect even better results.
Regarding the power used I did not think out the statement correctly as I
was thinking about the friction between the N/S wheels on the stock causing
more drag because of the friction but of course I had forgotten about the
decrease in rolling resistance due to the metal wheels. Oops.
Not to mention the axle pin point angles, (I've seem some models where the
fixed conical cup has the same angle as the axle (or worse, cup deeper than
axle!), so the bearing grinds round rather than ride on the pinpoint ).
I don't know about a brass to N/S interface, but electrical contact
through dissimilar material can lead to bad conductivity over time.
Gold plated v. tinned connector contacts are the usual area of
concern, and should never be mixed.