It is because the mass is further from the center of the axle. A large percentage of the mass is now 2" further away from center mass making it more difficult to rotate...even if it weighs the same as the old wheels. The further away the more torque needed to turn it. The difference can be felt.

 

The reason isn't JUST because of the increased weight of the wheels...it's the fact that the weight is further from the center of the wheel. The further away the rotating mass is from the center of the wheel the harder the wheel is to turn.

 

It's the tire width that makes the difference. I would be willing to bet that
if I put my 245s back on and did a dyno run I would have a measurable increase
in rwhp, like 2-5. You have a larger contact area, more resistance, and more
mass to accelerate. I can fry the hell out of my 245s just about anytime I
want in 1st gear, but with the 315s I can just grind them a little. If you want
your power to create the most acceleration then the latter is preferred.

 

Reciprocate is not rotate. My mistake early in the thread. Sorry about the brain fart.