oh to report back to this, i run mine at 51, and..... its kinda a rough ride, i noticed the interior would rattle more. feels almost of the quality as if i lowered the car.

 

I haven't had time to experiment too much with tire pressure. When I first took delivery of my Fit my tires were underinflated. I simply inflated them to the cold pressure PSI recommended in the door jam. Which on my 2010 Sport is 33 PSI all around. The ride seems fine and my gas mileage has just about been EPA sticker exact.

The concept that The Fit is front heavy and thus a differential between front and rear should be maintained makes sense to me. Therefore I probably will experiment with bumping the front tire pressure up. I'm not into looking for best high speed track performance and or trying to reach hybrid hypermiler MPG's, so I'm not going to do anything drastic. Maybe maintain the recommended 33 in the rear and bump the front up to 35.

Not too exciting but I do think tire pressure should primarily be maintained for safety, then secondarily for what goals the driver wishes to reach. Be it driving comfort, speed performance or MPG. For me, I want the best compromise for all, which I think means staying close to the manufacturer recommendation.

 

I'm keeping mine at 35.5 in the front and about 34.5 in the rears. Going higher is only going to give you a harsher ride and tire wear right in the middle of the tread pattern

Remember, the what the tire can handle is not what you go by, its the sticker inside the door jam that you go by, always.

 

I've run 51 (max pressure indicated on tire) in my Kumho's for over 30,000 miles and I do not have uneven wear. The ride is harsher, but I can coast longer.

Other tires may give you uneven wear at max pressure, but mine don't.

 

You have had the same experiences that I had .... The rough ride was more pronounced with the heavier stock wheels, tires and springs due to unsprung weight but the rotating mass would allow my car to coast farther than it does with lighter wheels and tires, but of course there has been an improvement acceleration so if I was driving in an urban environment I would be seeing a mileage improvement.

 

Hi! You're best tank is amazing. How did you do it? I am currently using 195/50/15 and I notice that I lost mpg compared stock tires.

 

Lots of pulse and glide (note: I usually use a different method than true P&G; instead of accelerating to the desired speed, then shutting off the engine, I use DFCO by coasting in gear), lower speeds (around 50-55), lighter foot, higher pressure tires (mine allow for a max pressure of 51), and in an area I'm familiar with, I sometimes shut off the engine on long downhill sections, then turn it on at the bottom.

On that particular tank, I had 2 other things going for me: I was the only one who drove the car (family members usually borrow my car a couple of times per week), and virtually the whole tank was spent on the freeway.

EDIT: My performance modifications also contribute to fuel economy somewhat, with the exception of the Blitz throttle controller. Intake, header, and exhaust let the engine breathe more freely, and my particular intake also allows warmer air into the engine, allowing it to use slightly less fuel and more spark advance in most circumstances. Lightweight rims require less energy to accelerate (but don't carry as much energy for coasting).

 

I just recently picked up the new family '10 fit sport manual.

After just over a week of owning it (and a tank of gas) I decided to check the tire pressure. (The tires were cold)
To my surprise the dealer had actually inflated them properly!
Well, they were slightly higher than the door jamb recommendation (33 all round). I measured between 34.5 and 35 for all four tires.

Going on some user input on this site I decided to increase the pressure slightly to an even 36.5 front and rear. It seemed to me like a happy medium.
Slightly more responsive steering, slightly increased mpg, and keeps with the weight ratio that honda recommends. Btw manuals have a 62/38 weight distribution which is slightly less than those with the auto box (64/36). One more reason to get stick shift!

Anyway back to the point. The trip computer gave a reading of 32.1 Mpg after the first 230 miles at which point I filled the tank to the brim. I later calculated that the average was closer to 31 Mpg. As the car is new this information is useless for scientific purposes. I have read plenty that there are all sorts of break in periods for the engine, tranny, and tires among other things. All in all I'm really happy with this great little car. I don't think you can have as much fun in such an economically feasible car.
Will keep postin!

 

This particular item has reached mythical status. It is still hotly debated on fuel economy and hypermiling forums. There are tons of reports from hypermilers running very very high pressures and not seeing any uneven wear.

I personally think it is a holdover from the days of bias ply tires, perhaps even the early days of widespread use of radial ply tires. I don't think it is as applicable to any modern day tire of decent quality as it was, say, 20 years ago.

 

just did a few trips of 100 miles. about 40.3~ miles per gallon according to the calculator with 51~ PSI and the trip back was 38.9~ miles per gallon on the way back.

before this i was getting like 34-36 around there with factory inflation with was like 32~ PSI.

but that was just 1 testing.. i wish i made the trip all the time to really test it.. and i might have gotten better then 40 as well if it wasn't raining the whole day while i was driving.

 

The radial ply sidewall and belted tread cuts rolling resistance down and and was a major selling point when they finally started marketing Michelin radials through Sears in 1967.... The sidewall resilience is compromised at high inflation pressure and increases rolling resistance on all but the smoothest driving surfaces.

 

35 psi. I don't like to ruin my shocks with super stiff tires. And reduce traction too.

 

The stress on shocks only comes from the unsprung weight and spring rates, absolutely nothing to do with tire pressures. Except for mud, sand or fresh snow, higher pressures increase traction. Low factory recommended tire pressures are driven by one overriding factor, customer satisfaction with ride comfort. Even tire pressures F/R in nose-heavy FWD cars increases understeer, which is considered "safer" handling for the general public. The front end always slides out first, by a very wide margin.

I run the Camry 40/35 and that has greatly improved the handling balance over the recommended 32/35. I will experiment with the Fit in the same way. 62/38 percent F/R weight suggests 46/29 but that is way too extreme. 44/40 will be the starting point.

Edit: 44/40 was great for handling in the twisties, but way too sensitive on the highway. 40/40 for now.

 

Think about it, with the increased tire pressure, the area of contact between the tire and the road decreases which decreases friction (i.e. traction) and that's not good for safety.

Here is my thinking about the shocks wear.
The tire that is overinflated and is very stiff, is like a wooden tire, meaning that it doesn't absorb shock as a properly inflated rubber tire would, so the shock goes to the shock absorber at a much higher frequency and intensity than it would otherwise if the tire was absorbing some of it.

Hope it makes sense. Here you can read about the traction: Do Not Overinflate Your Tires

 

Stress on shocks comes virtually 100% from the rate of movement of the piston in the shock tube. The quicker it has to move the more stress and wear on the shock. Those used off road wear much quicker than those on interstates thanks to the increased speed and distance traveled by the pistons..

BTW, no experts say manufacturers recommended tire pressures are 'best'. For the most part they are first chosen by the sales department for the comfort to the driver and passengers and second for performance. Generally speaking if you add 5 to 10 psi to the recommendation you'll get performance first and comfort second.
Optimum tire pressures are determined by the weight, suspension, tire size, and performance spercifications. Not many drivers have the same specs.

 

How the times have changed. . . I've been driving vehicles for close to 47yrs. For all that time each vehicle manufacturer has recommended a specific tire size and inflation pressure to go with each specific vehicle. These recommendations are based upon the specifics of each vehicle as designed and are presented to provide a safe and comfortable ride for that vehicle and it's occupants.

They are recommendations from the folks that designed and built the ride. As consumers go we tend to listen to the marketers. And there are a whole bunch of them who want as many of our $$$'s as they can get, thus we have choices. A simple look at the oil controversy that exists in most auto forums is another prime example.

I do believe there was a time when a buyer of a new car would have a choice of what brand tire to put on the car to be delivered. That certainly isn't the case today, but the sizing and PSI recommendations for that size are there.

I often change the tire size when I replace the stock tires to improve the handling characteristics of my ride. The changes are slightly off the recommended so I stay close to the placard PSI as long as I'm seeing even tire ware. I do feel comfortable w/ a 4-5 PSI increase to tighten things up, but what I NEVER do is go below the recommended levels.

The experts agree on this approach. Do the research. NASCAR crew chiefs use it to an extreme to win big bucks.

The MAX pressure on the tire sidewall has little to do with your vehicle but everything to do with that particular manufacturer's particular tire. Unless you understand this I would be real hesitant pumping to that pressure.

At least up until the "Hypermillers" came on the scene. A 21st Century term. Safety aside for the extreme - this group is obsessed with exceeding the EPA's MPG ratings for their vehicles. It isn't that hard until it becomes a contest. You go girl.

CleanMPG, - What is hypermiling An authoritative source on fuel economy and hypermiling

Extreme over inflation helps attain the goal. Easily understood, but it comes at the expense of ride comfort, handling, tire wear and road noise. These guys will go 50% above the MAX sidewall pressure recommendation.

Can you do that? Sure, I guess. But the question is do you want to. Why try to make a Honda FIT anything more than what it already is?? As stock it's one hell of a little car - who can argue at 40 MPG when driven in a sane manner.

Curb the obsession - bump it up 4-5 PSI over what the manufacturer recommends and you're doing all you can.

Beyond that your sujecting yourself and others to risks that just aren't worth it IMHO. Some of those have been expressed in this thread very well.

Always remember - Rubber Side Down_K_C_

 

[quote=Krimson_Cardnal;858508]How the times have changed. . . I've been driving vehicles for close to 47yrs. For all that time each vehicle manufacturer has recommended a specific tire size and inflation pressure to go with each specific vehicle. These recommendations are based upon the specifics of each vehicle as designed and are presented to provide a safe and comfortable ride for that vehicle and it's occupants.


No, they are based on th cheapest tire they can get andthe softes tride they can impress you with. Didn't learn that in 47 years. Bet you voted for Obama too. Whew!

 

The size recommendations are just that, from the folks who designed the vehicle. What your whiny ass goes out and buys is a whole other thang bro! K_C

 

I have had to up the pressure in the back tires on pickups and a van to 60 PSI to carry heavy loads of newspapers from the loading dock as they came off of the press to my district... we all did it without problems except for one guy that had big off road type tires on his truck that kept having blow outs...It turned out the manufacturing date showed that the tires he used were of old stock and had deteriorated over time.... In other words don't do this if you are running on old rubber and if you see a great deal on a set of tires check the manufacture date, even if you don't run high pressure, the rubber is probably dried out and they will wear out very quickly...

 

If the mfr is so smart and safe, how did the Ford Exploder fiasco happen?

Ive also been driving since back in the days when a 5000lb station wagon had 8.25-14 2-ply rayon bias ply tires as OE, inflated to 24psi. Comfy, but not very safe, and they lasted about 10,000 miles. Today's absolute worst Chinese replacement tire is superior to the very best OE tire from the '60's.

We got Firestone, U.S. Royal, Goodrich or Goodyear, no choice, but what brand the mfr had under contract. German cars always came with Continental, Italian cars with Pirelli, British with Dunlop, French with Michelin. Dunlop got tied up with Sumitiomo, so Dunlop OE tires on Honda motorcycles back then and our Fits now.

I never go below the mfr recommended pressure, or above the sidewall maximum, but do experiment, carefully, in between. I am reluctant to change tire sizes today due to clearance and issues with ABS and other systems that may depend on keeping close to stock rolling radius.