On the J15 I have now ended up with two types of driving wheels, one being an old set of Sharman 5'2" 16-spoke pin between, and a currently available set of AGW wheels which are marked as 5'0 16spk, but pin inline. The Sharmans are very slightly too big in overall diameter.
The tyre wear allowance that was commonly adopted in steam days was to permit up to 2" in wear before new tyres were needed, so the AGW wheel is suitable. BUT...and there's always a but....the crankpin is inline with the spoke. The available photos of no.186 as she is now clearly show crankpins set between the spokes.
When a model is moving, nobody's going to see that kind of detail, but when at rest it's something you can't unsee once you've noticed it.