I wonder how highway mileage would increase, on mt. Fit, if you put taller tires on it? It would sure drop cruising rpms.
The speedo would be off, and you would have to use a Scan Gauge to check speed and mpg.

 

I plan on getting taller tires when these crappy dunlops shit the bed

Dont think you will notice any difference if you stay under 24.5 inch tall tire (stock is 24 inches)

Any differences would be very minor.

Im only doing it to fill the fender a little bit as I plan on staying with a 15" rim whether its stock steelies or aftermarket

 

It won't really help you because RPM doesn't determine mpg.

If RPM was the determining factor for mileage, then the AT fits would get better mileage since they have a taller 5th gear (or final drive, I'm not sure).

The taller your tire, the lower your RPM at a specific speed, the more you have to press the accelerator pedal to maintain that speed, the more open your throttle body will be, the more air enters the engine, the more fuel your computer feeds the engine resulting in more fuel consumption than you'd have with the OEM tires.

Just think about it, Honda spent millions of dollars engineering your car. They didn't throw that specific tire size on the car as a joke. They did a lot of testing (more than some guy on the internet talking out of his ass) to figure out the perfect tire size for the car.

 

The car will also have to work harder to get up to speed with the effectively taller final drive and heavier weight.

 

Taller tires are a bad idea. It isn't going to help MPG and it will just throw your alignment off. As far as filling the wheel well better, it's not the way to do that either, you're better off to lower the car. A taller tire might fill the space a little more but it's also going to raise the entire vehicle and look goofy.

 

Nothing wrong with a slightly taller tire on the Fit.I'm not talking drastic change in diameter.It will also fill the wheel well with mild drops like Swifts when you do not want to go lower.

I've found a vast difference in manufacture specs for the same size tire as well.In my case I moved up to a 205/50/16 from the stock Dunlop 185/55

the 205 Kumho is a couple lbs more 20 vs 18lb but OD is less 24.1 vs 24.2
I could find a tire from a different manufacture with different specs in some cases both same weight or shorter /taller then the Dunlop

I considered going to a slightly taller tire like a 195/55/16 same as the CRZ that most list as 24.4 OD to fill out the wheel well with my Swifts

The thing is I can also find the same tire from General that list the OD as 24.0 and is no heavier then the stock Dunlops.I doubt I would see a drop in mpg one way or another when making such a small change.

also acceleration would not be affected much at all as long as you keep the wheel tire combo the same or lighter then stock.

I say give it a try and see what you find.I usually go to the manufactures website for specs as they can differ from say Tire rack or others.

Some of you guys act like he wants to put Dubs on his car lol

 

OP is way too focused on the cruising RPM. If anything, the taller tires will be heavier and hurt your MPG.

solbros already said everything I would say.

 

It's not that, I just think it's stupid to throw you're speedo and possibly alignment off for a different tire size that's not going to give you any performance benefit at all. IMO it's just messing with something for the sake of messing with something.

 

^Don't bother, zilla8 just throws out ridiculous statements in hope that someone will run with them.

 

^^ Nicely put and you are correct regarding the gearing statement for A/Ts as well as how the driver & vehicle will have to compensate for the larger sized tires.

Define "much".

Whenever I had my 205/55R15s Yoko AVID V4Ss on my Konig Quizs they were within 1 pound or so of the factory GD Sport alloy with a 195/55R15 Dunlop SP31. Despite this and the SP31 being a LRR (Low Rolling Resistance) tire, my GD was noticeably slower when accelerating from a stop with the same throttle input that I would have used with the factory wheel and tire set. I noticed that I actually had to feather the throttle more around town to get/keep the torque converter closed while putting around in 3rd, 4th, or 5th gear.

Later, I mounted the 205/55s on some Tire Rack Motorsport C1s while they had about 5/32s tread remaining. Acceleration effort was of course improved due to the lighter weight of the wheels... however, after later ditching the 205/55s with 3/32s tread remaining for some brand new 195/55R15 Yoko AVID ENVigors the difference in acceleration was almost like night and day. I could actually dart off from a stop and when cruising around 30-35 MPH keep the torque converter locked while in 5th around town again.

I'm not sure what the weight of the 205/55 V4Ss were when they were at 3/32s but their OD was still taller than that of the 195/55R15 ENVigors.

 

I do not doubt any of your findings and in fact like how you put all of the relevant info
in your post.It just seems hairs are being split with this one.

I'm sure with the A/T even a couple of lb's difference at each corner can make a difference as far as accelerating off the line.

In my case going to a slightly heavier and wider 205 has not made a difference in my acceleration.I also have a A/T but my ECU has adapted to my driving and it shows.

I will not even entertain a few of the other comments in this thread

Op just do your research and have at it and enjoy your Fit.

 

When it came time for new tires on my son's Fit, I went with a slightly wider tire but with the same ratio...thus a taller tire. I wanted to increase the height of the car and get a better ride, which is exactly the results I got. The ride is much better, and no difference in MPG's. Unless you do something drastic you won't have alignment problems either. Despite what some are saying, Honda did not spend huge amounts of energy determining a perfect tire size, for even a particular tire size different tire brands can result in actual tire size differences. Just stay within a reasonable range..in my case I went with a P195 tire width.

See page 3 of this thread:
https://www.fitfreak.net/forums/2nd-...droedge-3.html

Mine is the blue Fit with the Yokohama tires...several pictures and my write-up after the tires were mounted.

 

This was my experience as well with taller tires

 

So what I hear, is that final drive ratio in hi gear doesn't effect mpg, but an extra pound of tire weight does.
How come people are saying the a/ Fits get better mpg on the highway than the m/t its? Do you not think it's the gear ratio? Changing tire diameter, has the same effect as changing the gear ratio.
Am I wrong here?

 

The A/T Fits don't get better MPG on the highway.

 

I read the a/t Fit at 70 mph. has much lower rpm than the mt Fit. But this doesn't effect mpg?

 

It all has to do with physics.

In the case of the 205/50R16s on a GE8 Fit, one would have to be very "in tune" to their vehicle to be able notice a difference in acceleration since the difference between a 205/50R16 and 185/55R16 is typically difference of 1 or 2 tenths of an inch in diameter.

The difference in highway mileage is due to the transmissions' gearing. Generally speaking if 2 Fits were both doing 80 MPH down the road and one was A/T and the other was M/T, the A/T would be at approximately 3k RPMs were as the M/T will be at approximately 4k RPMs.

You are correct in the case of changing the tire diameter having a similar affect to that of changing gear ratios. Mind you, its not as drastic as actually changing gear ratios but it is noticeable.

To clarify going with a smaller than stock diameter tire would effectively be like going to a shorter gear (like going from a 3.55 final drive gear to 4.11 to help give you a better idea); which aids acceleration, raises your cruising RPMs throughout the range, but lowers top speed. The opposite is true with larger than stock diameter tires; which would increase top speed but lowers cruising RPMs throughout the range and hinders acceleration slightly (again, like going from a 3.55 final gear to a 3.08).

Note: The mention of the gear ratios do not reflect an actual gear ratio in correspondence to a tire size, its just to help those reading understand.

 

Someone posted " It won't really help you because RPM doesn't determine mpg. " I find this statement absurd.
If that's true, I should get the same mpg at 50 mph, in 4th gear, as I would in 5th gear.
Tell me I am wrong, and I will go away. I will, but I will be laughing as I go!

 

You are placing too much emphasis on RPM. Engine load, not RPM, is the biggest determining factor in fuel consumption. You will net better gas mileage running out the gears (within reason, stay out of VTEC) with low throttle than you will short shifting.

"BUT THAT'S MORE RPM!!!!"

Yeah. Equating fuel consumption only with engine RPM is greatly over-simplifying something that has a lot more variables.

The most influential modification for improving MPG is the driver.

 

This is good stuff
I use to run a taller tire on the street to tame my 4.30 gears on my old Mustang
mpg was in the 9-10 range lol

I could be wrong but I think the OP is talking about a modest change to a taller tire
that would reduce rpm's a little on the hwy and possibly gain a little mpg