Posted by casebro on Monday, February 12, 2001 at 9:29PM :
In Reply to: Re: From 16.5" to 19.5" Rims Question posted by mike stone on Monday, February 12, 2001 at 4:51PM :
You'll still be pusing 5500lbs down the road with an obsolete engine.What you'll gain in gas mileage will be related to the percent of drag internal to the engine and drive train- only the parts that go slower.Since this is something like 20% of the total horsepower used,if you change gearing by 15%, what you'll save is 15%x20%=3%.
Re: rolling resistance of tires.Has it occurred to you that the bottom of your tire is stationary(it isn't skidding,so it's not moving in relation to the ground).With every rotation of the tire each segment of it must stop completely, than restart, than accelerate to twice the speed of the vehicle at the top.than slow to a stop again at the bottom.This takes horsepower,the bigger(and heavier) the tire, the more H.P.required.Did you ever wonder why trucks don't come from the factory with bigger tires in these mileage conscious days?
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