[mentholatum132]

while doing my math homework one day, i came across a question that was about the circumference of the car tire and the mileage of a car. obviously, increasing the circumference of the car tire will mean less mileage.

so just wondering, does anybody do that?

[Chioster]

I think it has to do with since the circumference is larger, it takes longer to finish 1 rotation thus if the cars computer is still reading the old wheels circumference, it will eat the same amount of gas while taking longer to finish 1 rotation.

But for me, I just stick to stock wheel sizes. If I increase the wheel rim size, I will lower the aspect ratio to compensate.

[jakex1]

bigger = more power required to spin the wheel, more power required = more gas consumed.

[visuelz]

Technically if you have two wheels that weight the same but one has a larger circumference than the other, the larger one will look like it's getting less mileage due to odometer and speedometer's change of accuracy. Basically, the speedometer is saying you're going 60 but you're really going 62. And this affects the odometer similarly.

[90th.degree]

EDIT: Crap, I guess someone beat me to the whole thing about upsizing=speedo out thing. However, I want to get narrower tires on a wider wheel, throwing out the speedo even worse than the example, so I'm willing to put up with it.

[Tuffcore]

Sometimes when i blaze up, i think about stuff like this too. Wouldn't it be awesome if someone invented a tire that would expand once the car hit a certain speed so the car can go faster and farther on the same amount of gas? And then shrink smaller when the car is in stop position for faster acceleration?

[jakex1]

Sometimes when i blaze up, i think about stuff like this too. Wouldn't it be awesome if someone invented a tire that would expand once the car hit a certain speed so the car can go faster and farther on the same amount of gas? And then shrink smaller when the car is in stop position for faster acceleration?

if something goes wrong with those wheels, for example, one wheel expands the other doesnt, u are screwed.

[terrorist]

try helium tires. maybe you'll float your way to your destination. 0mpg?

[azn akira]

if the cars computer is still reading the old wheels circumference, it will eat the same amount of gas while taking longer to finish 1 rotation.

the cars computer doesnt give 2 **** about your speed, that's not a factor at all in it's fuel management system

the only real way this would work is if your car had relatively small wheels to begin with, and had very heavy (steel) wheels. you could get an 1'' or 2 bigger light weight (read expensive) wheels and low profile tires. the result would be a tire with a slightly larger diameter and less weight. however the amount of money you'd spend doing that would never be made up by the increase mpg.

the reason why just increasing tire size probably wouldn't work is that not only are you increasing unsprung mass you are also increasing rotational mass. both of those are things you do not want as unsprung mass affects the car much more than sprung mass, same goes for rotational mass since its Inertia = MR^2. so you'd have a doubly bad scenario of just increasing the tire size. not to mention if you increase the tire size you are going to have more flex in the sidewall and your handling will become worse and you will also see a decrease in braking performance.

[charat]

this doesnt work, the larger the circumfrence, the more surface area the wheel covers in one roation, but the amount of power needed will increase. its all proportional. you will likely get less mileage out of your car by changing to a larger wheel. its not just math, it has to do with physics too.

[azn akira]

its not just math, it has to do with physics too.

the math is a physics equation...

this doesnt work, the larger the circumfrence, the more surface area the wheel covers in one roation, but the amount of power needed will increase.

it could work in certain situations, as i explained, it just wouldn't make financial sense

i'll work it out for you

say you have 15'' steel wheels which weight 18# with 195/50/15 BFG Euro TA's which weigh 21.06#
that gives you a circumference of 22.67'' with a weight of 39.06#

you then get yourself a set of spoon 16x8 wheels which weight 12.9lbs and run 205/45/16 Dunlop SP 9000 tires which weigh 17.8#. giving you a circumference of 23.26'' and a weight of 30.7#.

that's a 0.59'' increase in diameter and a whopping 9# less rotating unsprung mass per wheel

using the formula for rotating inertia i posted earlier you'll see that the larger spoon wheel and dunlop tire combo has lower inertia too.

therefore it is possible to increase the diameter of the wheels/tires while also decreasing the amount of energy necessary to move them. does it make financial sense? no, because i doubt you really notice an increase in mpg it would probably be less than 1mpg (but it would be there).

[charat]

the math is a physics equation...



it could work in certain situations, as i explained, it just wouldn't make financial sense

i'll work it out for you

say you have 15'' steel wheels which weight 18# with 195/50/15 BFG Euro TA's which weigh 21.06#
that gives you a circumference of 22.67'' with a weight of 39.06#

you then get yourself a set of spoon 16x8 wheels which weight 12.9lbs and run 205/45/16 Dunlop SP 9000 tires which weigh 17.8#. giving you a circumference of 23.26'' and a weight of 30.7#.

that's a 0.59'' increase in diameter and a whopping 9# less rotating unsprung mass per wheel

using the formula for rotating inertia i posted earlier you'll see that the larger spoon wheel and dunlop tire combo has lower inertia too.

therefore it is possible to increase the diameter of the wheels/tires while also decreasing the amount of energy necessary to move them. does it make financial sense? no, because i doubt you really notice an increase in mpg it would probably be less than 1mpg (but it would be there).

we arent talking about different wheels. we are strictly talking about changing the size. same wheels same tires just different diameter and radius. so no. it doesnt work.

[ghost]

we arent talking about different wheels. we are strictly talking about changing the size. same wheels same tires just different diameter and radius. so no. it doesnt work.

It's pretty much common sense to see different results going from a 45 series tire to lets say a 65 series aspect ratio. Increasing the width will also make the overall height slightly taller as well.

Alex was explaining multiple things so another thread like this will not be made as he CLEARLY explained the myth behind size/weight

Have a nice day

[azn akira]

we arent talking about different wheels. we are strictly talking about changing the size. same wheels same tires just different diameter and radius. so no. it doesnt work.

first of all the op never said "only" tire size

secondly, that is why i spent a whole paragraph in my other post saying that increasing only the tire size wont work, i was just showing how it could be done

thirdly, i was also responding to your stupid post about it not being just a math equation it is physics also, even though the math equation was a PHYSICS equation

stop trying to back track and cover up your mistake. your post seemed to be in response to mine, you implied that when you said that there was more to do with it than just math (i was the only person to use any equations).

either that or you just suck at english and need to learn how to organize your responses better

[charat]

first of all the op never said "only" tire size

secondly, that is why i spent a whole paragraph in my other post saying that increasing only the tire size wont work, i was just showing how it could be done

thirdly, i was also responding to your stupid post about it not being just a math equation it is physics also, even though the math equation was a PHYSICS equation

stop trying to back track and cover up your mistake. your post seemed to be in response to mine, you implied that when you said that there was more to do with it than just math (i was the only person to use any equations).

either that or you just suck at english and need to learn how to organize your responses better

well sorry mr. A-hole.

no need to get your panties in a twist. when i said math, i meant its not a simple math equation. and calculus was created to COMPLIMENT physics. so why did you reply to my coment saying that changing wheels and tires would work? yes it would. but thats not the question at hand. and yes, the OP did ask for just changing the diameter of the wheel. maybe you need the english lessons. dennotation and connotation.

so as once said: "stop trying to back track and cover up your mistake"

[Clix]

well sorry mr. A-hole.

no need to get your panties in a twist. when i said math, i meant its not a simple math equation. and calculus was created to COMPLIMENT physics. so why did you reply to my coment saying that changing wheels and tires would work? yes it would. but thats not the question at hand. and yes, the OP did ask for just changing the diameter of the wheel. maybe you need the english lessons. dennotation and connotation.

so as once said: "stop trying to back track and cover up your mistake"

OP asked about changing overall tire diameter or more specifically speaking, increasing tire aspect ratio.

azn_akira corrected you, which I find it ironic because you're the one getting it twisted. And if we're talking about proper english, stop referencing the "tire" as a wheel. They're two completely different components.

I like the fact that you're not going to refute akira's post about bigger lighter wheels and tires but the fact that he corrected you and is "not on topic".

[azn akira]

and yes, the OP did ask for just changing the diameter of the wheel. maybe you need the english lessons. dennotation and connotation.

im going to assume you mean "tire" not "wheel"...

i came across a question that was about the circumference of the car tire and the mileage of a car. obviously, increasing the circumference of the car tire will mean less mileage.

so just wondering, does anybody do that?

that is what the OP said. nothing there states that the wheel needs to be constant. there are two ways of increasing the tires circumference you can get a larger sidewall or go with bigger wheels

i meant its not a simple math equation. and calculus was created to COMPLIMENT physics.

you dont need calculus to figure this problem out, you don't need to use calculus to solve all physics problems...also if you meant that calculus was needed it might have helped to have mentioned calculus in your original response

don't you ever get tired of being wrong? first about the engines, then about the aero, and now this..

[jakex1]

im going to assume you mean "tire" not "wheel"...



that is what the OP said. nothing there states that the wheel needs to be constant. there are two ways of increasing the tires circumference you can get a larger sidewall or go with bigger wheels



you dont need calculus to figure this problem out, you don't need to use calculus to solve all physics problems...also if you meant that calculus was needed it might have helped to have mentioned calculus in your original response

don't you ever get tired of being wrong? first about the engines, then about the aero, and now this..

is that you mr.chan? and the other guy is the evo couple

[versep]

well sorry mr. A-hole.

no need to get your panties in a twist. when i said math, i meant its not a simple math equation. and calculus was created to COMPLIMENT physics. so why did you reply to my coment saying that changing wheels and tires would work? yes it would. but thats not the question at hand. and yes, the OP did ask for just changing the diameter of the wheel. maybe you need the english lessons. dennotation and connotation.

so as once said: "stop trying to back track and cover up your mistake"

yo i cant find a better time to say this so here i go: your hair looks hilarious.

sorry if i offended you