unless you go with a tire like the michelin GreenX or something with a low rolling resistance you probably wont notice much of a difference in MPG but you will definatly see a difference in the handling of the car.

 

That is not necessarily true. The taller the tire the less RPM's you'll run thus the less gas you burn. For example, my shelby charger came with 205/50/15. I threw on a taller size tire (can't remember the exact size) and I was turning around 400 less RPM at speeds. Problem with that is it throws off the speedo about 5 mph. Unless the tire he uses has an extremely bad rolling resistance getting a taller tire will net you better MPG, though the taller the tire the less handling.

 

You are correct but but there's more to a tire than the first damn number, however you are wrong about the latter statement. Have you ever driven a car with one size tire then another? If you did you would know that at the same RPM's you are traveling faster on the taller tire. The second number represents the % of the first number and determines height. take a 245/60/14 vs. 225/70/14 and you'll see that the 225/70/14 is taller and takes less revolutions per MILE. Yes, I'm not a dumbass I know we're talking miles not minutes. Hello, the bigger the tire the less revolutions it needs. Take a 10 speed bike tire and move it one rotation. Now do the same with a BMX bike, which do you think travels farther???? I remember what size I put on the charger. 205/50/ 15 have a RPM of 874. I had 195/65/15 and they only have to do 807 revolutions to go a mile. A mile is a mile dude, taller means less revolutions, less RPM's your engine is turning, higher speed at the same RPM means you are saving gas. How much is hard to tell.

 

You may be right or wrong. It's not always the case that if you run a larger diameter tire that you save on mileage. While a larger diameter tire will have you turning less RPM at the same speed, that doesn't always equate to better gas mileage. For example, on a turbo car, if you are having to use more throttle under a higher load table in the ECU and making a couple pounds of boost on our car for example, your mileage may very well decrease.

 

Well he never did say he was going to run Taller tires and the fact is that if he does go with a 225 he would be within 1% of the same height as stock.

BUT if you go bigger you increase the angular moment of inertia (AMI) of the tire/wheel assembly. Which is the amount of torque reqired to get the tire turning thus you would actually lower your Fuel Economy expecially if you do a lot of stop and go driving.

I would suggest staying with the same size tire but just run a bit more air in them to help lower the rolling resistance of the tire. I always run 42-45psi in my tires and still get even wear across the tire.

 

All I can tell you is this. I ran a taller tire on my charger, at speeds I was averaging at least 400 less RPM's (engine RPM's). In other words with stock tires at 70 MPH I was doing 3000 RPM's. Taller tires I was doing around 78 MPH at the same RPM's. My gas mileage was better on the taller tire. Also, you'll get better gas mileage with the turbo's NOT kicking in as much. I proved that when I averaged between 25-30 coming out to NM with my TD05's installed vs. the normal 18-22 I used to average with my DR650's.
As for MeTrzan, did I ever say he was going to run a taller tire?????? NO, I simply stated that if he was going to have a chance at better MPG he'd more than likely have to run a taller tire. Also, a 225 will have less area on the road meaning less friction area. The example you posted is a taller tire. Like I said, if you've never tried running a taller tire and seeing the difference in it then you might want to either try it before spouting off.

 

if you've never tried running a taller tire and seeing the difference in it then you might want to either try it before spouting off.

Actually i have ran different size tires on many different cars and the only one that I have actually seen any kind of difference was my jeep wrangler going from 31x1050's to 35x1050s and let me tell you I had to push the gas pedal a lot further to keep the same speed.

But anyways I'm done with this internet pissing contest....Feel free to get your last word in....:rimshot:

 

If you keep the aspect ratio the same, then the larger section width has a larger circumference and will travel a longer distance for the same rpm and gear. However, the taller tire reduces the final gear ratio numerically----(higher gear). They call those highway gears because they give you better gas mileage on the highway, but will usually reduce your city only mileage so its kind of a wash. For some engines attached to lighter sub 3800lb chassis, that make alot of torque, in the sub 2000rpm area, the reduction in gear ratio does not really affect the mileage much so overall there is a gain in mpg average. On my GTO, just putting a slightly heavier flywheel in the car dropped my average 1mpg and same went for the larger diameter wheels unless you bought really light wheels. The manufacturers actually do alot of testing and so the tire and rim size they go with is usually the best overall (power and mpg) solution given a $$$$ restraint for the whole package. On a modern car, most of your mileage increase will come from tuning and getting rid of cats or weight. On a turbo car, its load dependent so a taller tire will make the turbo spool up more and again it has alot to do with power curves, weight, stock gearing, engine displacement etc---turbo evaluations are a little more complicated because of load dependency of turbos.

Sam

section width(#in MM)xaspect ratio(percentage)=sidewall height of a loaded tire at recommended air pressure in MM so the diameter is the sidewallx2 converted into inches plus the diameter of rim.

 

I saw tire rack comparisons of "green" tires and some of them failed to even beat normal tires in mileage BUT they all did terrible in braking tests. The actual gains for the best eco tires were not worth the purchase, especially at the cost of a huge amount of braking power.

 

I'm not the one getting into a pissing contest here. All I was saying is that I went to a taller tire and I saw lower RPM's on the tach. It's not rocket science, taller means less rev per mile meaning less engine RPM's meaning less gas burned. Hell, I went to a slightly taller tire on my stealth and dropped a couple hundred RPM. I don't know why you had to "smash" the gas pedal. Going to the taller tire more than likely messes with performance as I noticed difference in the performance, but that's not what this guy was asking was it? Don't need to get your granny panties in a wad.

 

If you think of the engine to drivetrain as a fixed system, switching out tires is equivalent to changing transmission gear ratios. Lower rpm = less gas. Also, our turbos kick on around 3k, so how you drive is a massive factor.

 

This is a classic case of hijacking the original question posted by wantboost, and going into your own sidebar and deep peeling the onion on a different aspect of the tyre size question.

The OP only asked changing section/width!! Not the circumference, not the height, and not the wheel. Jesus.

 

Aww heck, I really wanted to let @sskhaliq know it is a 22 year old thread. Probably older than he is, but he is gone already....

What makes a guy join and within 1 hour start ranting? FDS...Forum Derangement Syndrome....

Seriously needs to relax-haha
wherever you are dude, here is a cold one for 'ya... and chill....

P