35 psi all the way around here. The Fit feels great there to me.

 

40 all around, and smoother riding than the day I brought it home.

How? 205-50R16's in place of the stock 185-55 OEM tires.

Stock pressure on the 205s with stock (16x6) wheels felt less stable at high speed.

 

Stupid question how do you know the pressure limit of a tire? Mine have been replaced from stock

 

Yes what is NVH?

 

First, higher pressures will assist cornering and better mpg as any tire engineer will tell you. The upper limit is the reduction in tire contact area becomes enough to reduce cornering force. The lower limit is the inability of the tire to resist side forvces or impacxts with thr rim and the loss of mpg .having been a member of tire discussions with supplying tires to manufacturers those 'recommended' tire pressures are based on primarily comfort, not performance; marketing always thionkds cusomer butts are far too soft and require much caressing.
As for tires wearing out in the center with higher pressures, that is correct even with radials unless you do a lot of hard ciornering to even the wear. The advantage of radials is the ability of the tire to stay round, not lateral flatness. There is an optimum pressure that results in a round tire with contact patch for road surface involved. And the tire construction has a very important part in tat equation.
There is no perfect tire or tire pressure for all surfaces. Chose the pressure you find works best for what you want in the tires you have.

As for equal pressures all around you may want to consider that the weights on the rear tires are 2/3's of that on the front, so for most street applications about 4 or 5 psi less in the rear than the front will balance handling better. Unless you carry passengers.

And yes, exceeding maximum tire pressure is hazardous, not because the tire will blow out, but because the traction is severely reduced, depending on the tire tread and rim width.Tire engineering is a diificult technical excercise.

NVH is noise, vibration, and harshness, attributes both tire and vehicle manufacturers spend billions and billions and billions ...

 

I run 34psi cold all around on 205/50/16 Kumho 4X with good results

 

Has anyone managed to locate and English language version of he owners handbook/manual for a 2002 Honda Fit? Thanks.

 

currently running 36psi all around. can't tell any difference from when i ran 40.

 

Noise, vibration and harshness.

I run 35 psi all the way around. Little bit less rolling resistance but still very close to the door sticker as well.

 

just inflated to 40 psi today. damn tpms light turned on. it seems like i have to inflate tires every month.

 

FYI, inflating the tire more then factory recommendation adversely effects handling and fuel economy and not always in a good way. Tires are meant to be pneumatic, that being said adding more air to the tire does NOT reduce rolling resistance. The tires are suppose to deform to irregularities in the road, having too much air in the tire reduces its deflection abilities which wind up as lost momentum. Ever notice the dolly wheels thats are air filled is easier to roll with load rather then a dolly with a solid hard rubber tire? Ever tried to go over a bump on a sidewalk with one of these hard tire dolly over a pneumatic tire? You practically get stuck in the cracks of the sidewalk.

 

Sidewall max, 44 PSI cold. Ran my last set of tires 40K on a Toyota Corolla at 44 PSI, no unusual tire wear. Road noise and ride harshness are about the same as the Corolla, not bad.

 

really?
How come showroom stock racers increase tire pressures by at least 10 psig? And what is your definition of 'handling' ? lap times on a race course? softness of ride?
adding psig to your tires decreases rolling resistance as any tire engineer will prove. And you too.
Tire deformation to match road surfaces is a function of the tread compound and design. The tread contact area does not vary directly with tire pressure. Its much less than direct. Tires aren't balloons.
With less tire pressure the deformation of the tire structure is greater and the work the tire has to do to deform - and undeform - resujlts in more effort to turn the wheel; that's the reason for less mpg and less performance attributes. That applies to lateral forces as much as radial ones.
Actually pneumatioc tires on a cart require more effort to push that solid wheels. Easily demonstrated.
Pushing a solid wheel of the same diameter is easier to push over a bump than a pneumatic tire; assuming that the pneumatic tire deflects enough to reduce its impact with the bump does not make it easier to roll over the bump.
Sorry, but taking such manufacturer's recommendations as gospel ignores the manufacturers own caveats.

 

Oops doubled posted stupid internet connection...

 

Were talking proper tire inflation, what you're talking about looks to imply more about under inflated tires over properly inflated tires. The tire pressure also has a lot to do with load being carried as well, and tires design, and its use I'm simplying implying more is not always better. I'd rather take the oem placard tire pressures rather then some dufus on the internets recommendation to put max psi on a tire, Honda did more homework on what's best for the cars attributes on handling, fuel economy and safety. I've never seen any factory car ever come with recommended psi even near max pressure.
I mean what would be the point of putting in more then recommended air? So you can get what 1-3% better fuel economy while reducing traction? Yea I'll take my chances with what the Honda engineers say its best for this car.

In a concept of racers, a slightly lower psi tire has much more traction then a higher psi tire, autocross racers increase psi to add in steering response and feel, they aren't trying to get fuel economy lol.

Guys who race bikes run nearly 10 psi lower then oem on race bikes, the tires grip way more with 29psi rear and 28 front. Factory spec is 36/42psi on most sportbikes. But that is another subject at hand.

 

All tires deform when rotated. The circumference has a flat part where it contacts the road; the smaller the flat, the more round and the less rolling resistance. a lower tire pressure in a tire often will have less traction due tgo uneven deformation of the tread so reducing pressures in snow and ice conditions is not a given.
The proper tire pressure varies by tire construction and its a range, not a set pressure. Tires specifically designed for racing often have a range lower than street tires due to construction.
I've been a part of Honda tire testing and I assure you the 'recommended' pressure is nothing more than the pressure that most buyers and owners will find pleasant to drive. Not tyhe most economical nor best cornering.
Its not a good idea to promote the 'recommended' pressure as the best; each driver must decide for themselves. And for Fit tires the tire pressure range is 28 to 42 psig. Not necessarily 32 psig.
As an old tire engineer I have a different opinion on who's the dufus on the internet.
Enough.

 

At above 33, I can't power out of corners worth a crap. I really see what you are saying, and am not disputing the points you make. Perhaps the front becomes too light as it squats, but at lower psi, I simply have more grip. 35F/32R resulted in about a 5 mph loss on exit ramps because the rear end wanted to slide. I've got a rear sway though. Tire pressure settings on this car make a huge difference to the handling dynamics, and I really can't find anything I like more, or that holds grip in corners better than 33 in the fronts. I will continue to experiment, especially now that I have wider wheels with a lower offset. The car has much less of a tendency to get out of shape with this setup than it did a few weeks ago on the stockers and 205s.

 

You run counter to every autocrosser and track runner by saying you get less traction at 35 psig than at 32. Just what tires are youi running and the tread depths?
tire prfessures, alignment, brand, size, and tire compounds all majke a big difference.
And is your ramp uphill or downhill? Sloped? That, too, mastters a lot.

 

@ Mahout... You covered just about everything, but front to rear rake angle, spring stiffness, travel and damper setting... I've also noticed that that on fresh unworn asphalt, having higher pressure in the tires provides better traction but will cause traction problems on worn surfaces... Very worn concrete is treacherous stuff when tires are overly inflated... Cold weather and high performance tires is a bad combination regardless of the tire pressure used..

 

Ive never had better traction with higher pressure per say, i mean realistically speaking, I need to clarify if that guy A running 33psi vs someone running max tire pressure of 51, i doubt guy #B will get better traction then guy #A. Thats what im trying to put across, i used to drop my 90 300ZX twin-turbo rear tires to 27-28psi to hook up, it sure as hell didnt with 36, and no it wasn't a race tire, it was just a plain summer street tire Kumho Ecsta MX.