Aftermarket rims refer to wheels that are not originally manufactured by the car company but are instead purchased separately and added to a vehicle later on.
My mileage was off with a similar setup because I had larger aftermarket rims and tires, which means the car travels a longer distance for each rotation. (mechanics.stackexchange.com)
I was a mechanic in the service, so not a problem, tires at 50k intervals, I put aftermarket rims on it after I lost a few hubcaps on the road, this vehicle has been a great investment and good amigo. (edmunds.com)