Wider tires may use a little more gas. I consider the extra grip worth it.
Bigger
to clear the wider rear tire
Yes. Bigger tyres=> more friction => more strain on engine=> more fuel used
All types of friction increase fuel consumption. Wind resistance. Tire resistance. (The bigger the tire, the bigger the contact patch, the more resistance.) Engine parts, etc.
Depends. It's not the rim diameter that's important, but the overall diameter of the rim + tire combo. If the overall diameter changes, your odo and your speedo will be off. Bigger diameter, they will read low. Smaller diameter and the'll read high. But if you can go for a bigger rim, and a more low profile tire, then it's possible to ge the overall diameter to stay the same, and your gauges will still read true.
There are two, a bigger one in the trunk under the spare tire, and a smaller one somewhere under the center middle of the car
Because they rotate more to cover the same mileage as tire.
The smaller dimension of the donut spare tire requires more inflation than a standard tire. The correct amount of inflation for a donut spare is 60psi.
Tractors have broad tires because there is more contact with the ground and less compaction. The bigger the tractor tire the narrower it is a 52" tire is narrow but we have a 32" tire that is 34" wide.
A guage/ auto electric or speedometer shop can recalibrate the speedometer to adjust for bigger or smaller tire size. Why do you want to know that?
no it will not. Bigger rims (wheels) will make the car faster in a straight line but more difficult to turn. Smaller ones will have the opposite effect. The speed difference is about +- 2% of whatever the speedometer is reading.
Depends on the vehicle. It could improve mileage or lower mileage.