Greenwich Wheels - what size should I be getting?

[Lawrence]

Hello All,
I have at last been inspired to commence scatch building my first rolling stock. I am using Peco wagon chassis as donors but would like to replace the wheels. I would like to do this first before I fit Greenwich Couplings. I will use Greenwich wheel sets and ask is there a "standard" size? I appreciate that I may get a range of opinions and that the larger wheel sets would rub on the chassis! Also, excuse my ignorance but to what part does the "6.2mm" on Greenwich wheel sets refer. My Peco wheel sets appear to be about 7.2 flange to flange and 6mm tread to tread (widest).
Many thanks,
Lawrence

[Hugh Norwood]

I bought the 6.2mm wheels.

[Graeme Dunbar]

The diameter is that of the tread, but I'm not sure if it is the maximum, minimum or mid-point. I'm not confident of getting calipers to the right place. I guess that mid way on the tread would make some sense, being the presumed average value.

[Robin Webster]

Hi Lawrence, I too purchased the 6.2mm wheel sets. As i build my own turnouts to NMRA standards i would have a little problem of the Peco wheels riding the guard rails.The Greenwich wheels resolved that problem.
Hope this helps. :)

[JulienW]

As a general point about railway wheels the diameter is that measured across the tread (the flat bit), and not over the flange.

As GraemeD points out the 'flat bit' of the tyre is in fact slightly cone shaped so its diameter is larger closer to the flange, but if I'm honest I'm not 100% sure where on the tread the diameter should be measured but tend to do for the maximum nearest the flange and this tends to agree with the number on the packets of Dundas wheel I have in stock.

[Lawrence]

Many thanks for all your helpful responses - very much appreciated.

So, 6.2mm diameter looks like a good guide.

As a beginner there is so much to learn and so many products to choose from. This can lead to its own form of mental inertia. Similarly, whilst I learn far more by making mistakes it does eat into my 009 budget.

Best wishes,
Lawrence