How to calculate the widest tire my uni can use

Danke, Ich lerne Deutsch jetzt, und ich lerne mit meinem Einrad zu Bergen. (Not sure how to say that last bit … but I am learning how to ride mountain bike paths with my unicycle)

Oh, yes, I am reminded about an english expression we have that is like it that you may be aware of “it’s the cat’s meow” about something that is everything you want. (I had a Hans Dampf tire on the 27.5" rim which is made by the company Schwalbe, which I think means something like “Jack of all trades”, or it does everything well … so that is a little like “Eierlegendewollmilchsau” too.