AF Legacy Challenger

I can't assist on the traction tire replacement, but I suspect it's because you would have to remove the rods and valve gear to replace the traction tires. 

Mine runs fine and sounds good (admittedly only on my Christmas loops when I run my Hirail/Flyer stuff.)   Here's mine posed on my scale railroad:

The Challenger comes up second to the Y3 as the best Lionel/Flyer steam locomotive, (my opinion) mainly because of omissions from what was advertised (crew figures, oil bunker per prototype.)

Rusty

I have changed the tires on mine and it is no problem.  They took many hours of running before it was needed.  

I recommend the challenger.

I have two Challengers, a UP and an NP. My recommendation is buy one if you have the room to run it. Appearance and size wise these are right on. The sound is good. I recommend you look at the review and interior pictures at tuveson.com if you have not seen them.

Some operating observations. The speed range on these is very high. In conventional at a given voltage these run at least twice as fast as either the Big Boy or the Y3. In Fact, these run faster at 12V conventional than any of my postwar Gilbert. My floor track loop has 29" radius curves, no way I can run them at 16V and keep them on the track, the other 2 can be run at that voltage, if desired. In Legacy they are still fast, I use a high momentum setting and stay in the first 15 speed steps for realistic operation. The real railroad speed feature on the Cab 2 is useless, the speeds are way too fast. That feature works perfect with the BB and the Y3. Both of mine have marginal smoke production. It could be something I did, but all my other Lionel Flyer engines smoke normally. I see in the video on Carl's site his smoke just fine.