Caravan, tire options

I have a 2000 Caravan Sport with 16" Alloy rims with stock tires on it. I
want a 2nd set of rims to put winter tires on instead of having the tires
switched on the alloy rims at $40.00 a "pop" twice a year. No junkyard in
the area has 16" steel wheels, I'm not about to pay the price for new steel
wheels, or for used alloys but I was able to find a set of 15" steel wheels.
Does anyone know what the proper width tire comes on this vehicle with 15"
tires from the factory?

Thanks,
Snyde