I believe the Explorer/Firestone fiasco was a result of Ford not following Firestone's recommendations regarding tire pressure. Ford wanted to build a truck and sell it as a car [read tax incentives] so they didn't like the 'hard' ride given by following Firestone's PSI so they lowered it so mom's would like it. Too bad Explorer's started flipping over their decision.

Things like this go on every day in good old Corporate America. We are the ones who suffer. We are also the ones who need to be informed, and it's forums like this one that help serve that purpose. Be wary, however. I know there are shark hiding in the water - even around here. That's life. Ones objective is often clouded.

Back to our friends at Firestone. In the mid 60's they had a huge problem with the side wall blowing of their premier 'Firestone 500' tire as I recall. To me back then it was ground shaking. Such an iconic brand falling so so short.

Today no one bats an eye when Budweiser sells out to a foreign concern.
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"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."
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This is what I'm talking about. Understanding why we do something. Looking for reasonable results and knowing of consequences. Knowing you're drinking a cup of hot coffee and you really don't want to spill it. K_C_

 

False and false!

 

Ok, guys, I want to know why eveyone messes around with tire pressure. The recomended pressure on the sticker on the inside of the driver's door says that the pressure should be 33 psi on both the front and rear tires for correct handling for the vehicle. This also guarantees that the tires will wear correctly. If the tire is underinflated from this pressure the outsides of the tire tread will wear prematurley. If the tire is overinflated, the center of the tire will wear prematurley. Why does everone want to set the tires at max psi? 52 psi sounds like asking for the tires to blow out on the highway. Yah, maybe a little better fuel economy, but can someone tell me why the high psi?

 

#1 Nobody is recommending overinflating the tire beyond the spec of the tire.

#2 Modern tires do not wear out the center at the maximum end of the tire manufacturers spec on the correct width wheel

#3 Tires perform best at the upper range of the spec- less rolling resistance, less retained heat, maximum traction (on most common highway surface), and maximum load capacity

The only downside is increased vehice NVH, which is why I keep it near the door sticker (and why Honda does too). It's a balance of trade-offs.

Any questions?

 

 

I feel comfortable running 40psi, max is 44psi. I would consider running mid 40's if my next tire has a max psi of 51 and it is not winter time.

 

I use 40psi on my four tires. I used to have 32 on all 4 tires and then tried 40psi, after that my mpg went up.

 

I am a firm believer in running close to or at the rated pressure as stamped on the tire sidewall. 45 pounds all around on the Fit factory Dunlops (my Honda Valkyrie too). On our Honda Elements Nokians I run 50 psi and on my employer's Ford Exploder I run 50 psi in the BFG AT KOs. I think the handling is far better and the ride is acceptable.

 

The reason is simple: the factory spec is for average driving; some of us do somewhat more than average. Average drivers piddle around and and the pressure recommended is adequate for that. However, for those who think corner-carving and redline rpm is part of the driving mix, greater tire presuures are necessary, even up to the recommended maximum presuure limit. If we tried to use the 'recommended' pressure we'd end up on our sides.
And we haven't broached the subject of front-to-rear variances yet. Got an hour or two to spare?

PS the factory recommended pressures do not guarantee anything like tire life or handlind limits. They are mainly for the owners who think their car is a washing machine; i.e. to protect against the legal profession.

 

Wow, I'm really going to have to disagree with the "maximum traction" statement in # 3 above. The more pressure you run in the fronts the sooner the onset of understeer will occur. While a harder tire gives you faster initial turn-in maximum grip is lost since the tire cannot deform to the road surface as much. While this may not be very apparent on a Fit I can assure even an increase of 2 psi on my Miata will make a noticeable difference in max grip, I just run the sticker pressure of 29 psi and don't mess with it anymore.

On another note, my butt-o-meter can clearly tell that anything much over 4Psi above sticker is way to harsh for me. I run no more than 35 psi in the fronts for better turn in and 33 in the rears.

 

36 p.s.i on stock tires all around.41mpg on the highway last night!

 

The traction will increase as the pressure increases and then decrease with further pressure increases. Usually themaximum cornering will occur about 5 to 10% less than maximum pressure spec limit. Its why autocrossers and SS racers use higher pressures.Its due to stiffening the sidewall that stabilizes the tread contact profile. Understeer follows the traction when it falls off.
And high pressures do indeed wear out the center of the tread without wearing out the edges. Likewise too low pressures will wear out the sides before the center.

 

Agreed, it's not a linear thing, there's a limit to how much pressure you can put in before traction starts going the other way. At the track you'll be getting a lot more heat in the tires than on the road. At higher pressures on the road tires won't get warm enough for good grip. The tire pressure set by the manufacture is a balance of comfort, grip, fuel mileage and reliability. You can play with the pressure to improve one or more, but the others will suffer. My guess on my Miata is I don't push it hard enough to warm up the high performance tires, so any additional pressure above sticker just makes it worse.

 

32 front 34 rear.

It's comfy like that, handles how I want it to (for daily driving, no suprises), and I still get 37-40 mpg.

I raised it to 40 all around one time and didn't like the extra bumpyness. That's pretty much the only thing keeping me from raising the pressure.
I suppose if I were to go for a "spirited drive" i'd probably go 45/40 and lower it when I got home.

 

2.2fr (31.9psi) and 2.25rr (32.6psi) daily. On my track wheels, I start out at 1.6fr (23psi) and 1.8rr (26psi) and after a few laps they are at about 2.3~2.4 fr and rr (33.3~34.8psi). The A050s (track) have a very stiff sidewall, as do the daily AD08s for that matter and no need to run increased pressures as it doesn't help with FE at all (mostly because my foot is made of lead) and for me steering feel is decreased and just enhances more understeer.

 

I need to take you on one of my roads. 10 psi buildup not unusual.see one on utube road that makes dragontail look like an interstate or something like that.

 

Hope this doesn't mean you are driving crazy on them, take it to the track.

40ish front/rear for MPG. I know it rides harsher and there is a slight loss of maximum grip.

 

Sounds like alot of you put more air in the front tires than the rear, reason being because the front weighs more? What about when you have passengers and stuff in the back? Don't you think if the front weighed significantly more than the rear enough to effect the tires it would tell you on the door jam to put more air in the front tires?

 

Yeah, but maybe Honda is accounting for the extra load you're allowed, to the maximum allowable weight in the rear. I don't know if anyone has loaded their cars to max allowable weight in the rear and looked at all tires then. Maybe at max wt. both fronts and rears have about the same physical compression and surface contact. The pressures Honda expresses may be a happy medium between a single driver and fully loaded to accepted capacity. Most weight added to the car after the driver and passenger will probably be seen on the rear tires after loading, since it will be loaded over the rears for the most part. I think, that's why, people on this site have found pressures that are best for their type of usual driving. I know that if I carried some heavy tools around in the back of the Fit every day, I would find tire pressures that were best for my use. It's a fun topic.

 

I was chasing around with JCrimson one evening and experienced understeer along with snap oversteer while trying to stay with him through some curves.. I had rotated my tires that usually had 3 to 5lbs more air in the front than the rear and had forgotten to change the pressure... At the time JC also used less pressure in the rear tires... He has done so many changes to his car that I don't know if he still does or not.