1.875" bicycle rim width
There's no such thing as a &quot;normal&quot; wheel. There are different rim widths for different purposes. These are probably older mountain-bike wheels.
Regarding tire compatibility: a given rim width will be compatible with a range of tire widths. Different manufacturers may have slightly different recommended ranges, but this and this are good starting points. Note that this is using the width across the inside of the rim, not outside. My guess is that you'll be OK with 2.5&quot; tires, but I'd measure to be sure.