I recalled this old issue and thought I would share FWIW and see if I understand the issue correctly.
I purchased a new Genesis DCC (w/Tsunami) Challenger around 2012. I recall that an event occurred; i.e., a traction tire stretched and came loose. While able to push it back in place, that did not help as the stretched tire would again come loose.
Of course, the valve gear blocks simply removing the tire and installing another, so some of the valve gear needed to be removed. (I broke a piece and the Athearn repair guy (Wayne?) kindly sent me another, and advised how to go about the repair.)
Have others had this problem with the Genesis Challenger or Big Boy? I'm thinking that the good news of the loco having lots of traction also meant that the tire could be over-stressed with too many cars plus a grade creating too much drawbar pull for the tire. While this could also apply to the Big Boy of the same time frame, I never had the problem with it, nor the Challenger again.
Paul
Modeling HO with a transition era UP bent
I did have on a Rivarossi FEF but nothing modern.
A couple of thoughts come to me:
Those tires cost probably $0.10 each out the factory door. That's all costs, including development, contracts, any tooling, etc. They're made of God-knows-what, but it's carbon based and won't last long as pliable carbon compounds are wont to do. Oils and solvents will soften them, but so will ozone over time. They'll weaken, stretch, deform, migrate, tear, etc.
If you get a bag of them that were manufactured in 2009, or even in 2015, their God-knows-what is going to be well aged by the time you lay your hands on them to mount them in stead. It's like that bag of AA batteries you figure you'll use next Christmas in those musical thingies. Good luck with that.
I don't see why the entire drivetrain needs to come apart, certainly not the valve gear. At most, the affected axle must be liberated from its crank pin screw, at the which that one axle, only, can be dropped out and repaired........?? I don't have that locomotive, but it seems that it should be the same for all 25 year old scale steamers.
I would try to get the newest tires possible, and sufficiently small that they're a bit of a bother to scooch them over their retaining flanges. If they break, they're simply too small, but if you can get fresh, pliable, ones over those ridges, and properly seated, they shouldn't then go on to stretch a whole lot until age compromises them in turn.
I will stand to be set straight by those who have done this a few times and know better.
I seem to have jinxed myself by raising this subject. I powered up my Genesis 4-8-4 and guess what, a tire came loose. Putting it back in place was a waste of time as it quickly came loose again.
I was unsure where to get a reasonably correct replacement, not seeing it at Athearn parts list nor at MB Klein. So I e-mailed Athearn and hope to get a reply. Meanwhile, googling got me to the following site of which I was unaware. I did some measurements (wheel diameter, tire width and thickness) and ordered the closest thing per their recommendations, hoping for a decent fit. I ordered ones for the FEF3 but also for the Big Boy & Challenger.
HO SCALE TRACTION TIRES - DIESEL/ELECTRIC/STEAM LOCOMOTIVE , HO LOCOMOTIVE ENGINE TRACTION TIRE REPLACEMENTS (lovetrainhobbies.com)
I don't have the right (3mm) hex nut driver for the crank pin that needs to be loosened so I broke down and ordered a $15 small set from Amazon. I don't want to damage the pin by using pliers, if that would work. UPDATE: The small nut driver set arrived today; seems nice for the price.
https://www.amazon.com/ProsKit-1PK-9402-Hex-Nut-Driver/dp/B003TPSF32/ref=sr_1_5?crid=1S0V5TXOT7CMH&keywords=small+metric+nut+driver+set&qid=1636226501&qsid=138-3829610-8418653&sprefix=small+metric+driver+set%2Caps%2C102&sr=8-5&sres=B003TPSF32%2CB004E4AKKI%2CB000T9R2MQ%2CB000BQ4XPQ%2CB09CLNXC9Q%2CB094CDHZ11%2CB01J3O4RYS%2CB07G7X1HHD%2CB093L4RDGN%2CB099JX6B4Y%2CB000PDOIT6%2CB0009ORXQQ%2CB0992M7QF4%2CB0006OBFEK%2CB099Z7G4FG%2CB007BLZ7TK%2CB08RS29QVS%2CB091GQD1JM%2CB099Z9CV3D%2CB07G7GYBMV
Another argument for keeping the right items and tools available.