You’re the one that mentioned tractive effort, and now you’re saying it means nothing… hmmm. Yes, it’s theoretical, but it’s based on key characteristics. Train weight is very important in calculations, and you can’t simply ignore it. I could argue, for example, that NYC 999’s design is rather primitive when compared to British locomotives of the same era, and 112mph is simply not credible for such a crude, basic design… the fact of the matter is that the first 100% proven 100mph locomotive is Flying Scotsman, the first proven 112mph locomotive was Silver Link, and the fastest steam locomotive is indisputably Mallard - although the first locomotive to obtain a speed record in excess of 100mph and actually still be capable of operating immediately afterwards was Stanier’s Coronation.