Actually, re-reading your post, I reckon I did misunderstand what you want to do. Is your concern that you want to have the letters projected on the sidewall radially from the centre of the hub?

Perhaps you can do something like the following images? Work out the start and end positions for your complete text, do a circular array of the line markers, then on the vertical add each letter, rotate the letter from the hub centre into position using the line markers as your guide and repeat for each letter in the text. Finally, you can project the curves onto the sidewall of the tyre.

Alternatively, you could rotate the tyre, project, repeat.