will buying larger size rims affect my speedometer and gas mileage?

Question

i have 15 inch hub caps and getting the factory 16 inch alloy wheels. will this affect it?

Answer 1

it will probably help out with the gas mileage a little but will throw the speedometer off at least 3-5 miles per hour on it,but on fuel sometimes it actually helps it some,good luck with it.

Answer 2

YES! It will affect both speedometer and gas mileage. If you change either the rim or tire and the measurement from center of hub cap to outside of tire gets bigger then your gas mileage will suffer slightly and your speedometer will show about 2 or 3 miles slower than actual speed. Just measure the distance from the center of the hub cap to the tread on the tire while it is stock. then do the same measurements with the new set up. You're speedo will show about 1-2 mph under for every inch difference.

Answer 3

It is not so much the difference in wheel size as it is the difference in tire size. If the new tires are the same circumference as the old tires, your speedometer will be fine. If it is more or less than the original size, it could have an affect on your speedometer, as well as your mileage.

If you get the diameter of the new tires within about a half inch of the old tires, the difference should be very small if at all noticeable.

Good luck with your wheel upgrade!

Answer 4

It will also depend on the size tires that you put on the rims. If you check the diameter of the tires before you take them off, and replace the wheels and get a tire with a little smaller sidewall, then it may remain the same and nothing will be affected.

Anything you do that affects the diameter of the tire will affect the speedometer. It will also either increase or decrease the gas mileage depending on the drag that the tire creates. good luck.

Answer 5

Here is the fact. All these answers that say it doesn't matter shows they should shut up and not talk and they will be smarter. I designed tires at Goodyear for 5 years and know the physics involved. The critical thing is the overall height of the rim/tire set up. I will give you 2 examples 205/65R15 and 295/45R18. The first number is how wide the tire is in width. it is 205mm wide the 65 is the % of the width which is 205 X .65 = 133.25mm now convert this to inches by dividing 25.4 which gives you 5.25 inches. That sidewall is 5.25 inches from bead to tread. Now X it by 2 for the tire circle below and above the wheel and you get 10.5 inches. Now add the 15 "the rim" and you get 25.5 inches that how tall the tire is. Now for the second tire it is 295 X .45 =132.75mm/25.4 = 5.23 X 2 = 10.46 inches + 18 = 28.46 inches. Now 10% of you gas mileage is lost in you tire/wheels minimum. Every pound less in the required air and you lose 0.5%. But we are talking wheels. The first tire is 25.5" second 28.46" Now I can compute this for you too but I need to go. You lose on average 2.25%mpg the first inch over 4.5%mpg 2 inches over and 9%mpg 3 inches over 18% 4 inches over etc. etc. Think of it like a pry bar. If the weight is close to the tip you can lift alot of weight slowly. If it is far from the tip you lift faster but not as much weight. So to carry the weight at the proper speed your engine has to work harder. Also you affect the speed you speedometer says and your vehicle speed sensor is also affected to control your computer in reaction to your other sensors. SO TRUST ME IT MATTERS!!!!!! Todd

Answer 6

Try this: http://www.miata.net/garage/tirecalc.html

Put in the values for each, and what it will tell you is how much your spedometer will be out.

Bigger rims don't always mean bigger tires. What happens is that on most bigger rims they have smaller sidewalls, and therefore level off the size a little.

The size of the sidewalls is the number in the middle of the tire size example: 225/60R16.

I should tell you that if you use the 16's technically the ABS and everything else could be off a little, but shouldn't change anything. You'll probably be out 1/2MPH on the spedo, your call if that's worth changing at the dealership - I wouldn't.

Best of luck.

Answer 7

Not necessarily the rim diameter but if the overall diameter of the tire/wheel assembly is different than it was before then your speedometer will be off without a doubt.

Answer 8

You must remember that if it throws off your speedometer then it will throw off your odometer and if you use the wrong odometer reading you are going to get a misleading answer. General rule of thumb is the bigger the tire the farther off your speedo will be and the lower your MPG.

Answer 9

yes to both questions, it will throw the speedometer off and on the highway you will get a little better gas mileage.