I have a short section of micro engineering rail that I hand laid as an experiment. I just measured from the top of the rail to spike head with a dial caliper and came up with .027". An RP-25 wheel is .025" from wheel tread to top of the flange - so JUST enough room. I've push cars back and forth over it with no interference, except where poorly spiked.
I have some code 70 rtr micro engineering track and repeated the experiment there to get an idea of how high their molded plastic spikes are. Railhead to spike is .070", railhead to spike head ~.048" - a difference of only .022". This surprised me - the rtr plastic spikes look MUCH finer than the metal spikes.
Too close to call! I would think that ME would allow enough room for RP25 wheels - even the narrow guage stuff (where code 55 is more commonly used) I have seems to have RP25 flanges. My bet is that it will work, but someone with experience with the rtr code 55 track will have to make the call!
Hi fellas, I have on order some micro engineering "rtr" code 55 HO track (since May !) I've searched on the forum but did not see an answer to this question:cry: :- Do models with the RP 25 std metal wheels run ok on this code? ( if not i'd better cancel it quick!!)
I have peco code 83 on the main & code 75 on passing loops & some sidings,:thumb: but fancied the code 55 for some lighter use sidings. 
Has anyone used it on an HO layout?