You can change the rim size (or wheel size, I don't know) in TDUPE, but the algorithm of what the each wheel's size is is something I have no idea about, because for example when you pick the Dodge Challenger rims in TDUPE, the rims on your car will be huge so one could think that if you go for the biggest rims in TDUPE it'll have the opposite effect in the game. But no, it's totally random as far as I remember.
Going this DB/batfile thingymabob is complicated, too. First, if you change anything in the rims DB, you won't be able to have custom brand names in-game (i.e. BMW, Porsche, etc) and it will make the game crash. So you need to use only TDU names. The second thing is that you can only change the wheel size or at least I could. I've never managed to change the tire wall to be smaller or taller. I could only change the tire size only.
Maybe I am not smart enough and there's a way to do it properly... I don't know.