Changing the final drive gear doesn't affect the suspension. It will, however, void the powertrain warranty. If you're leasing, don't bother. It's a lot more trouble than it's worth (unless you like to work inside transmissions =P )

 

For what it's worth...our 1995 Civic was similar in size, weight, and power, but had a much higher (lower numerically) final drive. It was a solid 1,500 rpm less on the highway. It got the same city mileage as our Fit, but got about 5 mpg better on the highway.

If there was a higher final drive for the Fit, I'd be tempted to give it a shot. I think the stock gearing was designed with large cities in small countries in mind. I bet the '09 Fit will be heavier, but still get better highway mileage than our '08 due to having less gear.

 

Sorry, I wasn't clear. I was talking about the tires.

 

I think you're wrong.

What I'm saying is that to drive at a true 69 mph (according to my GPS) my engine revolutions are now lower.

So yes, rpms are lower with speed being a constant when comparing the stock tires to the new taller tires.

 

The labor and headache alone is making me cringe

 

If you change the final drive to something taller you will have your foot in it to keep up at speed.
And the engine will be lugging at lower speeds and rpms.
This thread is pointless..............

 

No, no I disagree, and I fully support the mans quest for the Holy Grail of automotivedom. Who wouldn't want to get 49MPG at 80MPH? So the car will take three days to get to 80 BIG DEAL Seriously though: to the OP, good luck in your search and keep us posted but you face an uphill battle. You wil probably find few willing to undertake such an ambitious project on a vehicle that already gets stellar gas mileage when driven with restraint.

 

What is the difference in weights between the stock tires and the taller Michelin rubber?

 

I'd like to combine a high boost KWSC kit with a more highway friendly gear. I think the combo of more power and less gear would put it on par with the Civic which has a higher hwy rating.

Maybe the end result would just be equal mileage to what we get now, but with relaxed 75+ mph cruising.

 

Its really not that bad to replace the gear itself if you know what you're doing. The problem I see here is that most of the gears offered, for most cars are going to raise your rpms, as they're meant for acceleration, not cruising.

 

195/60x15 tires typically weigh 19# and are 24.2" in diameter
195/55x15 tires are typically 18# and are 23.4" in diameter.

If he just cruises at not too fast constant speed I expect he will gain; if he does much acceleration he will lose. Increasing the rpm (acceleration) of heavier tires at a greater radius requires more power - and gas.
He might have been better off going with 170/65x15 Pirelli's, which are only 17# at 24" diameter. Gains in gearing, rolling resistance, and in weight. Interesting.
And a whole lot less difficult than changing tranny gears. You can't just chose a gear with more teeth, they have to match the other gears. Its not a motorcycle chain drive.

 

+1........

 

Very helpful, thank you!

 

I love when people want to spend money to save money.

 

I know. It's like buying a $27,000 hybrid car and then bragging about how much $ you save on gas when you can buy a car for half that price and save a lot more money.

 

That is true but im talking about spending $1000.00 and not $10,000 more on a hybrid, and still be in a fit. Because the fit will never be a race car in my book. Fit = family/road trip/grocrey getter/Daily Driver/Roomy/non-racey CAR.

If the fit pulls up hills fine in 5th gear for all the people that say it does why would I most of the time be in throttle on pretty much flat interstate with a lower 5th gear or final drive? That does not make much sense to anyone I have told my idea to and quoted that from this forum.

I have already put 195/60/15 on it. I am not as dumb as people think I am.

 

I think you should do it man. Get a machine shop that can make you the parts you need and install a taller final drive or 5th gear by all means.

The only way you are going to find out if thats going to get you 48 mpg at 80 mph is if you do it, so I say go for it.

If you outsmart Honda and make a better 5th gear ratio that adds +14 mpg to the Fit at 80 mph then you will be able to build that product and sell it for sure.

I think you should get working on those blueprints and start contacting machine shops and make your dream a reality.

 

Making a subtle and cheap change to your final drive ratio (195/60/15 tires) to keep your highway speeds (70ish) out of VTEC range (3400 RPM) is far from stupid. Please post your MPG results! Some MT Fit owners ARE interested! The weight of the tires should also be considered. All 195/60/15 tires don't weigh the same amount as the "specs" at tirerack will tell you.
Having a new final drive gear made would be cost prohibitive. All money saving tweaks should be judged on a cost/benefit basis. How long to recoup your money and what other sacrifices will be made (acceleration, warranty and city mileage)?

 

That's a very good point about the VTec kicking in: driving 65 is great for mileage (and I've gotten 41-43 at 60mph) but if you do it on I-95 around here you will be risking your life. Not sure exactly where the Vtec would kick in while cruising in 5th gear but if using slightly bigger tires will lower RPM's by a few hundred at a give speed (ie. let you run with traffic at 73 mph or so) without activating the vtec that would be a good -- and very inexpensive -- thing.

Anyone know where the numbers would break down (i.e., what's the RPM in 5th gear with the larger tires suggested)?

Frank

 

I'm not sure about the numbers but around here if you want to go 60 in the 70 zone it's certainly doable. People will hate you, scream at you, tailgate you and maybe shoot you. I was looking for a way to achieve, cheaply, lower than vtec RPMs (in 5th) while cruising at 72-74 MPH. This speed will keep me from getting shot, hopefully. There are many factors to consider. The Fit has a very upright profile and air resistance will increase exponentially with higher speeds. I've still never gotten a clear answer on what the GD3's drag coefficient is.