1995 Other Hyundai Models Tires

Other Category problem
1995 Other Hyundai Models Front Wheel Drive Automatic 200, K miles

Just bought this yesterday. There is a loud clunking noice seemingly coming from the rear of the car, drivers side. It is more noticeable city driving then highway. I also noticed that there are winter studded tires on the back - in good shape.185/70/14 but in the front (which are all season but need replaced) are 185/65/14. I am wondering if it is ok to have different size on the back - or does this make much difference. A mechanic is puzzled why the winter tires were put on the back in the first place.I have heard that on a front wheel drive, if studded tires are used, they should not be used on the front due to possible rack and pinion problems. There was no manual with the car. So I have several little things I am searching for answers for. But this clunking and the different tire size is the more iimportant then where the trunk release is! Thanks for your help!