A Farmall M tractor weighs just over 5000 lbs.
When we counted the number of M&M's in a 12.6oz bag, we got 404, which means there are 32.06 M&M's/oz, which means that each M&M weighs 1.13 grams.
12,000 to over 20,000, depending om specifics.
Empty around 35,000 lbs
My brother an i flip tractor tires for a workout. My guess is they're about 100 lbs per 1 ft tall. So a 5 ft tall tire is about 500 lbs. That's without a rim or air.
All tractors vary in weight from model to model and brand to brand. For a list on a number of tractors and information on them see the related link...