Lower MPG with bigger wheels?

[Gunner]

Has anyone experienced a lower miles per gallon after installing a larger diameter wheel? I am trying to find out if this is normal, or if something else is wrong with my car. I'll try to post some pics of my baby's new shoes next week after I get my digital camera. Yep, Christmas came a little early this year!!

[PTGT_Boy]

Depends on how heavy the the wheels are. More weight on the rims, less gas milage.

[Cal Cruzer]

quote:Originally posted by Gunner

Has anyone experienced a lower miles per gallon after installing a larger diameter wheel? I am trying to find out if this is normal, or if something else is wrong with my car. I'll try to post some pics of my baby's new shoes next week after I get my digital camera. Yep, Christmas came a little early this year!!

You could also read less HP on the dyno with a larger diameter wheel. They saw this result on one of the shows on Speed TV. They did a wheel swap and could not understand it. Ultimately it had to do with inertia and having the weight farther away from the hub and a bunch of other things that I don't understand how they work. Wish I could remember the name of the show. Was it Sport Compact or something like that? Anyone?

[Mike-in-Orange]

Cal, that was on Tuner Transformation. They put a bigger brake kit on the car, and although the weight of the disks was the same as stock, they were of a larger diameter. As I recall they lost something like 8HP at the wheels with the bigger brakes. Now image the potential loss if you add a heavier wheel and the extra weight is moved even farther out from the hub! As you move the weight farther out from the hub, or center of the wheel, it requires more power to accelerate this mass. You can basically test this yourself by tying a hex nut onto a piece of string. Try spinning the nut with about 6" of string let out, then try it again with a foot of string.

When I was racing bicycles I used to chuckle at the guys who were bent on getting the lightest hubs they could for their wheels, then not pay attention to the weight of the rims and tires. It makes even more of a difference when racing bicycles because YOU are the engine!

[Cal Cruzer]

quote:Originally posted by Mike-in-Orange

Cal, that was on Tuner Transformation. They put a bigger brake kit on the car, and although the weight of the disks was the same as stock, they were of a larger diameter. As I recall they lost something like 8HP at the wheels with the bigger brakes. Now image the potential loss if you add a heavier wheel and the extra weight is moved even farther out from the hub! As you move the weight farther out from the hub, or center of the wheel, it requires more power to accelerate this mass. You can basically test this yourself by tying a hex nut onto a piece of string. Try spinning the nut with about 6" of string let out, then try it again with a foot of string.

When I was racing bicycles I used to chuckle at the guys who were bent on getting the lightest hubs they could for their wheels, then not pay attention to the weight of the rims and tires. It makes even more of a difference when racing bicycles because YOU are the engine!

Mike has been paying attention. He will do well in the quiz today!

[Mike-in-Orange]

quote:Cal Cruzer Posted - 10/12/2004 : 1:31:21 PM

Mike has been paying attention. He will do well in the quiz today!

Oh crap, I hate quizzes.[]

[K9 Cruiser]

Hey guys, I beleive the weight plays a large factor in a posible minimum loss in MPG.However, it should be to a minimum I would think.

My question Is on size and speed. I used to go to the track and some peeps would switch there 17" and 18"s down to 16"s or 15" for track times. I heard that you run throught the rpm's and gears quicker. Which meant faster times. I have never tried this at the track, but I am sure others might comment on this.

So if this is true? Is buying bigger wheels just for show and handling more than Quiks? Jay

[Mean Green]

You know, I thought it might be in my head but when I had the 40's low profile Toyos put on my GT felt quicker. Maybe my feeling is correct. Smaller tire = quicker take off.

[robinjoe]

Doesn't the odometer count the number of revolutions the tires make and multiply that times the circumference?

If so, you are going a further distance with larger diameter tires than the odometer is recording.

Shouldn't you multiply your mileage X 1.058 (18/17=1.058) to get a more accurate reading?

Joe R

[quicksilverdon]

Inertia is one factor. Assuming you went to lower profile tires to keep the overall diameter of the wheel/tire the same, the odometer would be okay, but you've increase the width of the contact patch. As a rule, "skinnier", higher-profile tires give better mileage.