Do I want large or small metal wheels

[yellow_cad]

All my freight cars are fitted with metal wheels that I had enough of, but one set of 4 wheels had to little of a flange so I need to replace them with with medium or average flange. Trying to buy some, I find small wheels that measure 24.5 mm and large wheels that measure 31 mm, but I don't know where this measurement is taken. Are these measurements the wheel diameter not including the flange or just what?

 

[Greg Elmassian]

The convention is on the tread (you called wheel diameter not including the flange),
AND
is mid-tread, i.e. halfway between the outer edge of the wheel and the flange.

Since all wheels have a taper to the tread, measuring halfway gives you an "average"

Greg

 

[Gavin Sowry]

Trying to buy some, I find small wheels that measure 24.5 mm and large wheels that measure 31 mm.

Ah, looks like you have found the Bachmann wheels. By default, get the big 31mm ones. The smaller 24.4 ones are more for 'special' applications.
Opinions vary on the quality of these, but, overall, they do the job, and are economical. And, yes, diameter is taken at the middle of the tread.
Treads are tapered, as Greg said. Reason for this is to help wheels fixed rigid on the same axle, get around curves (you thought that's what flanges were for).
You see, on a curve, one wheel has to travel further than the other. With a tapered tread you, in effect, have a range of diameters, and the wheelset 'adjusts itself' sideways so that the individual wheels end up travelling their proper distance. Sometimes, what you think is flange squeel, is in fact the tread skidding when one wheel can't keep up with the other.
I recall inspecting a brand new wagon after it had travelled 400 miles from its builder.... the treads were all nice and shiney, and all the flanges were still rusty.

 

[dunnyrail]

As Gavin says, I have quite a few of the Bachmann 31mm on my LGB stock and have nothing but praise for them, well except for the odd wobbly or out of back to back one butbthese issues are easily sorted by gently npbending them to shape (wobbly) and pushing the wheels back correct back to back.

 

[Gizzy]

Another shout out for Bachmann 31mm wheels. These are also branded as Lilliput.

I have fitted them to quite a few of my LGB wagons as they are around half the price of LGB wheels. They run fine on my mostly LGB Code 332 track (I also have some ART and PIKO track on my layout).


The smaller 24.5 mm wheels are used for Feldbahn stock or similar....

 

[Gavin Sowry]

Another shout out for Bachmann 31mm wheels. These are also branded as Lilliput.

I have fitted them to quite a few of my LGB wagons as they are around half the price of LGB wheels. They run fine on my mostly LGB Code 332 track (I also have some ART and PIKO track on my layout).


The smaller 24.5 mm wheels are used for Feldbahn stock or similar....

Beware, on the modern Feildbahn stock (the small wheel stuff), the axles are different. Bachmann 24.5 will fit (just), but they bind, and won't turn.

 

[dunnyrail]

Beware, on the modern Feildbahn stock (the small wheel stuff), the axles are different. Bachmann 24.5 will fit (just), but they bind, and won't turn.

Yes I hit that issue but simply opend up the wheels bearings a little to make things work. But that has to be done with care, too much and you will find flanges scraping on the base of the vehicle.