Here are two Accurail covered hoppers. The one on the right has RP-25 tread and the one on the left has a "standard" tread I believe it is called. Interesting comparison. I am an infrequent H0 scale operator and really see no difference in operation. One person told me that the RP-25 tread would eventually damage standard frogs as they drop into the gap of the frog (tread is not wide enough) and then bang against the opposite side of the gap as they emerge. There was an interesting thread on this a long time ago. It discussed all types of H0 tread sizes including proto87. I didn't know there were so many different types of wheels. Edit: 33 inch wheels on the left; 36 inch wheels on the right.
There shouldn't be a issue with the standard.110" RP-25 wheel since these been around for the last 50 years and is the standard wheel size freight cars and locomotives come in...I'm told the semi scale.087" wheels are finicky when it comes to track work and will drop into the frog of the Atlas switch and crossing especially the C100 track... The real difference is in axle length which can vary between manufactures. I have learn that the older BB wheel set would work in several brands of trucks. As a side note.Years ago I used Athearn BB trucks on all brands of cars (expect Atlas) and had great success in improving the roll ability of those cars.. BTW..It takes several years of above normal operation to wear down the frog of the Atlas switch.
Don't take this as gospel, but I believe the wheels on the right hand car are code .88 threads, the one on the left is the standard RP-25 with code .110 threads. as far as I can remember NMRA code Rp-25 reduced flange depths to a standard depth and added a fillet between the thread of the wheel and the flange of the wheel. I don't believe that the code .88 threads are "standard" although they are a definite alternative if you have very well laid track and switches. Again, to the best of my memory, the RP-25 with the fillet were better than the variable deep flanges that went before. At about this time a lot of people became interested in using scale size rail. At the time, again using my memory, code 70 rail became more and more popular even among standard gauge modelers, not to mention narrow gaugers. The RP-25 can be used on rail as small as code 40. I can live with the over-size wheel threads, since doing a layout with scale rail can't see ever going back to code 100 rail.
I have understood that the RP-25 meant conformation to flange depth, and not the tire width. It is natural to assume that RP-25 weehsets will drop into some frogs if the frogs are grooved to allow for deeper-than-RP-25 flanges. If the frogs are grooved with a flange path only as deep as the maximum allowed for RP-25, the flanges should ride nicely on their rims throughout the frog. AFAIK, the RP-25 wheels don't work well on Proto 87 turnouts, and the Proto 87 wheels don't work well on RP-25 and other NMRA standard turnouts...if at all. I must admit, too, that I greately prefer the look of the thinner tires.
In the interest of the truth, I just checked the package of wheels. It says they are "semi-scale" 36 inch axles on the right hand car. For more honesty, I made up the term "standard" for the left hand car as I didn't know what else to call them. Having blurted out this confession and purged myself of the falsehood, I am going to take a nap as I am very tired. :shame: :smile-big: This is the same thing that happened the last time I tried to write about H0 scale axles. This is as bad as writing on the DCC and Electronics Forum.
You don't need to apologize for using the word "standard" for the left-side car, because as far as I know the RP-25 flange and contour along with .110 threads are in fact, the "standard." I seem to remember that actual-to-scale wheel threads would be on the order of about .65 or thereabouts. Makes you wonder about complaints about measurements on a loco or car of 2 - 3 scale inches, or a 2 degree variation on a radius.
Those thin tires sure do look good, but I wouldn't want to fiddle with trackwork to the degree that they would work reliably. My hat is off to all who model with scale rail, but I prefer code 100. I have too many "vintage" locos and rolling stock that like something forgivable.
This makes sence when your whole layout has finer standards. Then you has narrower flangeways.. A turnout will look much better. That's a half step to PROTO87. Wolfgang
Candy: This is the correct information for the pictures above. There are other wheel options besides these two. Here is a photo of a boxcar with Proto87 wheels. Wheel treads are very narrow.
