Has anyone installed a larger diameter tire and seen and can report on the lower RPM's and improved (if any) fuel millage?

I'm having fun eking out the best economy from my new Fit and it seems the free-way cruse RPM's are not the best for best fuel economy.

I'm also looking for other best bang for the buck changes that improve the economy. I could care less about the cars performance other than best use of fuel.

 

the larger tires will be heavier so it would probably cancel out any gains made

 

if your looking to lower your unsprung weight, the best place to look is the wheels. stock alloys and even steelies are on the heavy side. if you don't live paycheck to paycheck you can pick up some nice 11 pound alloys that will do what your looking for. they will even improve your off the line speed and throttle response.

 

I wonder if having a higher rollout would actually be noticeable?

Maybe the best thing (poor for bang for the buck though) is to go with the lightest smallest narrowest( similar to standard factory size) wheel with the highest profile tire (with low resistance rating) that would reasonably fit with a darn good amount of air in em. Maybe even capping the wheels (or close to it). And getting lighter lugs and ditching the TPMS.

so probably alot of that ^^^would net really teeny weeny results, but hey it adds up....but whether or not it would be SIGNIFICANT....idunno, I would think so to some degree though.

I am waiting for more responses too.

I just filled up my half tank again and to my Surprise!!!
I got 36.53 MPG! YAYAY
100% city (crappy socal/LA) but I did drive a little bit the other night when there was not much if any traffic, so that helped but still....me very happy. Now I really want that scangauge...MUUAAHAHAHAHAHA....

 

some one needs to put 4 spare tires on and find out.

 

ta daaa congrats


I like the 4 spare tire test good one.
PM me I'll give ya a shipping address......

 

Thanks

And I would love to see someone rock (but do it proudly) all 4 spares!
I think that would be illegal here though. I dont know for sure but here in Cali its illegal (maybe not really inforced) to sneeze with your window up! AHHAHAHAHAAA

I remember a news story where they tested a spare tire on like corvette and beat on it and it lasted really, really, REALLY WELL. But one should still only sport it for like 50 miles max. I bet it would be a horribly harsh ride though And the handling would be poo .

 

Snap I'm sure your right and it may bot be worth a test, but for the interest in econ I'd be game. With the scanner I'd know on the 1st trip.

Read most of the Vtec thread. Pretty interesting stuff.

It would be cool to see anyone with the light and a scan gauge report some real MPG changes . That may have to be my job.

 

DOOOOO it.....DOOOOOOO IT......

 

Yeah, I've got larger diameter tires on for the winter, because I like to be able to drive through some deep snow. It seems pretty effective for that. I didn't expect the 3% reduced engine speed to make any big difference, and far as I can tell it doesn't.

Fuel economy dropped noticeably, though some of that will be because the odometer thinks the car hasn't gone as far, and driving on snow much of the time doesn't help either. But even on highway trips and adjusting the mileage, it seems to be not quite as good as with the lighter stock tires. That could be just because of the colder air for all I know, but big heavy tires probably don't help.

Aerodynamics, dude. I'll be working on that in the spring, trying to find out if that rear bumper is as much of an air brake as it looks like it is. And light-weight wheels, yeah, but that costs money.

If the engine RPMs are high enough that you think it's a problem, you're going too fast if you're aiming for fuel economy.

 

WOW now why didn't I think of that...

 

one thing to keep in mind, if you change the overall diameter your speedo will be off... if your speedo is off so is the odometer. Its hard to tell gas millage when the mileage is off.

 

larger wheels/tires = better highway mpg
But sucky city mpg

 

Not to mention a harsher ride the lower the profile is. I find the Fit to be harsh enough as it is stock.

 

I wonder if the lightweight multispoke wheels from the Civic HX "fit" on the Fit? those along with some low rolling resistance tires (whatever the Prius uses) might make a difference.

No matter what you do to the car to improve the fuel economy, it's going to be 90% driver, 10% mods.

 

Looking close at the wheel well clearance with the stock Sport tires, I do not see how a larger diam tire that would be big enough to make a difference would even fit.

FYI I looked up the design size for the Fit tires
Base 175/65 14
22.95": Diam 906.3 revs/ mile

Sport 195/55 15
23.44": Diam 887.3 revs/ mile
Here's a like to the calculator
Tire Size Calculator - tire & wheel plus sizing

So the sport tach will be 2.1% less STOCK base model
interesting. I think that may explain some difference in mpg and rpm data I have seen on here.


Anyone know what it would take to swap the finial gear ratio?

Looking around on the web or some answers, I ran across this. It's an interesting read.
GD3 Honda Fit Jazz VTEC Full Review

 

You'd probably have to find a company that does that sort of thing, and gather enough interest for them to make the part, then leave your car with them for a few months while they designed a new one.

It would probably be cheaper to just get a 1.3 i-DSi engine and transmission from a euro Jazz and swap it in.

Not sure what you mean about the tach being less? If youre at 3000 RPM at 60 MPH it will always read that whether you have 15" wheels or have the car on a lift with no wheels at all. The tach and speedometer readings are all internal to the engine/transmission. The only thing that varies with your tire size is your real speed.

 

I do not think so. As the drive tire roll out gets smaller the eng will have to run and a higher RPM for the same MPH. The other side of that is why I posted this thread, knowing that a gear change would not be easy. Larger tire roll out will lower the eng RPM's at a given speed with out a doubt.

 

I have and I believe it has a huge impact on the highway, I averaged 44mpg on one occasion over a very long distance trip.The tires were heavier and I suspect my city miliage was most likely down. I detailed the trip some time ago... (see post #3)
https://www.fitfreak.net/forums/eco-...79-40-mpg.html
Using closer to stock dia tires later on I got lower results.

 

Yes this would be true if you are measuring with a GPS. If a stock car shows 3000 RPM at 60 MPH on the tach/speedomoter, swapping to larger wheels won't make the speedometer register any different, as the speedometer gets its speed reading from inside the transmission. Yes the car will actually be moving faster, but the dash will still be reading 3000 / 60. You would need a GPS to measure the error created from the size change.