Been many years and I am now older, dumber, an forgetful, but I THINK it was either 28 or 32. I think the former allowed use of original fenders but 32's required after market plastic replacements.
I wanted the wider tire for bike trail or bad surface street use and the alloy wheels and plastic fenders offered a significant weight reduction so I went with them. Bike was a lot easier and more fun to ride but still had the look of a stock bike. I did a couple of other mods like alloy handlebars, 3 piece crank, and replaced that awful rear derailleur
I kept all the original parts and when I sold it was a simple matter to make it factory original again.