Tires and gas mileage?

Question

I had an argument recently with my friend about Tire size and gas mileage.

He says a larger tire will get you better gas mileage. I say that the tire the car comes with, is in most cases, the size that will give you optimal fuel efficiency.

He says that a big tire will get better gas mileage but why does a toyota pruis have small tires? Why, if big tires get better gas mileage, would a hybrid vehicle get better gas mileage?

His argument is that one revolution of the tire would get you father on a larger wheel. While this is true, the tire would also be heavier and take more force to move that distance.

Can someone please help? Any answer especially with a nice mathematical or logical one with get a thumbs up and possibly a "best answer".

Thanks

Answer 1

what is milage. ummmmm umm um um read your instruction book

Answer 2

I would say the best tire to use is the size from the factory. If you have tires that are bigger they will require more work to rotate. Also the speedometer would read slower than what is actually being driven. I had oversize tires on  my pickup and they were a rougher tire and the speedometer read that I was going 5MPH slower than i was actually driving. The odometer would be off to. The smaller tire would probably be better for gas milage, but will set your speedometer as going faster than what is being traveled. I would stick with the stock size tires. The engineers designed the size for a reason.

Answer 3

The only thing that will matter is the added weight. All the friction that is overcome is within the vehicle and will not change with simple the tire size. However if the transmission had not been calibrated for the tire size then it may appear as though you get better gas mileage because the odometer will read incorrectly as it will no longer know how far you actually go.

The odometer works by counting revolutions per minute based on the stock tire size....so if the tire has a longer circumference then everything will be altered. Not to mention the coefficient of rolling resistance....how much power it takes to keep the wheel rolling....

It more or less comes down to weight and friction...less weight+less friction=less power to move it=less fuel used to create power.

hope it helps...you should argue about proper inflation next...;)

Answer 4

It makes perfect sense either way. With larger wheels also comes more weight, therefore there needs to be more power. So more gas will be used. Also with larger tires/wheels you need to adjust you transmission on engine components so you mileage will be accurate

Answer 5

True, a larger tire, under some circumstanses, will give you better mpg, because the engine is turning slower for the same speed.

But, that is why overdrive was invented, to gear up the engine so it is turning slower at highway speeds.

And then 5 and 6 speed transmissions were invented which replaced the overdrive, and had the same results.

Bottom line depends on your engine and transmission. At 65 mph in top gear, what is the engine RPM? 3000 or over, then you may benefit by a "overdrive". maybe, it depends on whether or not the engine has any excess power at that speed.

I used to have a Jetta that reved over 3000 at 70 mph, it would have benefitted from an extra gear. My passat revs 2400 at 70, probably not.

So, the problem is that there is no yes or no answer, it depends on the various factors, including your tolerance for lower power.

If you do change sizes, don't forget to have the speedo readjusted.