Wow, I thought you were an autocrosser. If you were you would know that higher-than-mfg-recommended PSI almost always results in higher cornering and braking performance. From what I've read that's true for Fits with stock rubber as well.
Logically you're correct, but the fact is that manufacturer's recommended pressures are always a compromise between perfromance and ride quality. Heavier vehicles get bigger tires, not higher pressures. That's the only way the manufacturers can keep the pressures low enough to ensure a 'boulevard' ride.
All of the tire mumbo-jumbo on this forum really amazes me. Measuring pressures hot instead of cold, getting hyped up about 40PSI as though it was dangerous in any way, whisper-down the lane stories about tires exploding solely due to air pressure -- innuendo, rumor, and misinformation, the lot of it. It would be laughable if there weren't so many people buying into it.

 

It's called FUD wdb. And the world LIVES on it...Spread by the media and devoured by the public.

--D

 

Ok, I am guessing you missed the winky face at the end of that statement. I was basically highlighting the fact if people want to get anal about safety then running the recommended PSI's is the "correct" way; also the fact that the Fit maximum axle loads probably does not accommodate 5 people in the car. Mostly I am just poking fun at people who cite safety and then deviate from those reccomendations.

Not sure why you quoted me with this statement, I always use cold PSI as my reference. You can check every post I have put up on this forum as proof of that. Infact the only time I start dealing with hot PSI is when I am trying to optimize handling between runs.

With that said I have pretty much proven (at least to myself) that running over about 42ish PSI in my vehicle is dangerous as it diminished the handling and braking capacity almost exponentially past there. I personally don't think risking my life during an emergency situation when I could be relying on that extra performance is worth running those kinds of pressures. But everybody has different values, I feel a bit disheartened that maybe one day somebody will injure myself, my family or somebody I know because they were intentionally running incorrect tire pressures trying to save a couple of bucks on gas. I am not targeting hypermilers here, really I am quite indifferent to people that use absurd PSI's and people that use all-seasons in areas prone to have snow. As we all know saving a few dollars at the expense of other people is nothing new.

With that said I have already acknowledged that profile size, width and compound may play an important factor in the performance of tires when it comes to PSI. My tires should never be maxed out past 42psi, other tires will have different thresholds.

Anyway, the basics are simple here. If you run more than your sidewall max pressure (cold pressure to clarify) then you do risk a blow out and it would be your own damn fault. Where the line is as to how much pressure you want to run between that and your recommended is a grey area.

 

Not so much missed as misinterpreted. Mea culpa.
That was not directed at you specifically; it was more of a generalized statement of incredulity that your post brought out, for better or worse I guess.
I'm sure you've documented this and I would love to have the link. I took my tires up to 50, hated the staccato ride and unresponsive back end, and lowered them to 45. That's my number-of-the-moment but if you have evidence supporting 42PSI then I'll be out there first thing in the morning pssing air out of my tires.
I am 100% with you on this. I guess I get put off by some of the stuff you choose to put in bold print.
I've decided that I am not, and can never be, a hypermiler. At the moment I'm declaring myself to be semi-hyper. I do believe we have more in common than we do otherwise. The stacks of tires in my, uhh, 'garage' attest to it!
Okay, max 'safe' pressure is grey. But "risk a blow out" is black-and-white hyperbole. Show me evidence please. Mind you, I've been in the same room with wheel/tire combinations that have the capability of removing body parts in the event of a 'blowout', i.e. the rim pieces separating themselves from the other rim pieces and the tire. Not only that but I was the guy putting air in them at the time. Like HST said, you have to show me.

 

Don't hold your breath.
The Eco Forms Tire Nazi's do not have a single documented issue to back any of this shoot from the hip expert gibberish. Also they ignore the documented information from commercial and police departments that said it's better.

I have 8300 miles on my sport Dunlap's with flat ware pattern 1.5/32nds used and the car stops and corners way better than needed with non race driving.

 

ahhhh, these segregated conversations make me dizzy

Ok, really we are not that far off on a lot of these. Granted I did go on a bit of a rant before

I want to clarify that I keep saying that MY VEHICLE and MY TIRES (apologies in advance for the bold font) would be dangerous to run at higher than 42psi because it dramatically decreases the ability to maneuver safely during an emergency situation. I also keep saying that in other peoples vehicles with different tires may have different thresholds.

People can argue all they want, but if you exceed the max sidewall pressure on your tires and it blows up on you (either in your face or on the highway) the tire manufacturer is going to wash their hands of any liability and place it squarely on you. Whatever the repercussion, it is your fault. You blow up a tire and kill a family or somebody in your car as a result of 100psi tires (And yes, on that CleanMPG forum people are doing that)... well good luck in court.

The grey area is between the recommended and that max pressure. At least you are within safety tolerances of the tire if not the vehicle. Sure you may be reducing your handling and braking at a certain point, but at least you won't fly out of control on the highway because the tire separates or blows out.

Obviously people can't stop people from using these techniques, the most I do is try and keep people informed and aware that there are some risks accocisated with it. However that doesn't mean people are not going to protect themselves. Me personally, I carry a pressure gauge everywhere. If somebody nails me and I suspect they are trying to save money on gas by running excessive PSI, I won't hesitate to check the pressures and use it as a way to sue for negligence later on.

This is a newer trend people are following in times of high fuel prices. Once it catches on enough and car and tire manufactures realize people are pushing their safety factors to extremes & a few tragic results occur it will trigger more rules and legislation to be put in place. Who knows, a few years from now a checkstop may include a pressure check.

Yes, people are clearly Nazi's when they have other peoples safety and well being in mind

That article you found also mentions that a lot of establishments run recommended PSI's. It isn't exactly a sanctioned article from the police force, it is one mans opinion just like anybody else's.

 

Oh noes, the N word. Thread lock!
Sorry, it's a very old habit.
Agreed.

Hows this as a general rule:
Below factory recommended pressures = danger zone
Car manufacturer recommended pressures = comfort zone
Reasonable amounts above car manufacturer recommended pressures = better handling and braking performance at the expense of ride quality and/or noise
At or below tire manufacturer (sidewall) maximum pressures = still safe but not optimal for much other than fuel economy; ride and handling both compromised
Above sidewall maximum pressures = danger zone

 

Actually not bad

 

I have noticed my Sport Dunlaps loose air fast.
Like 10psi in 4 weeks.

You may want to keep an eye on that

I plan to check them every fill up ( ABOUT 2 WEEKS) from now on.

 

Interesting,

Both my summer and winter tires seem to stay right where I put them for pressure for months on end.

The only excpetion is when I got a screw in the front tire and I had to add air for a week until it got fixed. I lost about 2psi a day from that.

 

Maybe it's the heat here. Maybe the elevated pressure???

Poor records, but I'm pretty sure I set them at 50psi just before the 4th of July. Found them at 43 (all 4) yesterday.

thanks for the comment

 

Not sure, could be because there is more outward force it is escaping around the rim easier. I wonder if you fill up with pure nitrogen if it would help. Maybe just the tires?

I never ran the stock tires more than about 10k before I swapped them out for some Toyo snow proxies.

My tires are even usually perfect PSI after I pull them out of storage which is surprising.

 

Could be more than one thing such as:

1. microscopic holes in your tires.
2. valve stem not holding air properly
3. maybe there's water in the tires from compressing water vapors

or it just might be the heat. I remembered having the (!) symbol pop up on me during the cold morning. The day before was very hot and I did a 40 mile run. This was with the stock dunlops too.

 

My money is on the fact you check your tire pressures when the tires are hot instead of when they are cold. You have no consistent basis from which to measure.

Even checking them "cold" will result in a 1 or 2 pound change within the same season, depending on the ambient temperature. Seasonal changes will be even greater, e.g. winter 'cold' pressure will be markedly lower than summer 'cold' pressure. Given all of that variability, checking your pressures after driving the car throws any hope of consistency right out the window.

 

I used to drive a heavy camry and took corners really hard and had taken it to an auto X event and it will loose air due to the pressure you put on the tires. Simply carrying more people, cargo will make your tires loose air faster.
I want to try nitrogen. I just read the GTR comes with nitrogen because they believe Air is too unstable. haha.

Anyways, the best way to check air pressures is in a closed garage where no uv rays can hit the tires and doing it in the same temp. My pressures are consistent when those conditions are met.

 

Thought you guys would like this:


Sorry for the crappy Crackberry pics - again

Nail in the tire since yesterday morning while driving around the town I work in........NICE! I knew I heard and felt something on the tire but I stopped and checked two times and found nothing(I thought it was a rock(s)). So, I drive around for lunch and drive home. The car did not handle different just the sound and a little bump when rotating and it seemed to go away on the way home(driving faster, i guess).

Notice the tire pressure gauge is at 55psig, all the tires were at that pressure and it is 70 degrees this morning(if it were that temp year round!). I have said before I roll at 60psig but that means I have driven 5 miles to the air pump at the gas station and it was like 90+ degrees out side. So, with the change in temperature at least 20degrees I have lost 5psig(paul, thought you might like that)

Also, this is good info to know that you will not blow out if you encounter a nail running 60psig or below. I know that has been a big concern of many people and my own. Proof is in the pudding people.


Needless to say, I have reduce all tires to 45psig and I am taking my car to the tire people from them to patch it(patch number 2 - thanks to the town that I work in). I will see if the tire people can tell me how much tread I have left on my tires, since I can't find a tire depth gauge at the auto parts stores around here.

 

Wow lucky.
And dang thats high psi - over max on the sidewall. But that's good news to me that you're still rollin. haha.

 

Ok, here are the results of my 36k tires...........tread depth at 5/32.

 

My latest change to the Fit has been tire pressure, increasing it from 28psi to 45psi this weekend. I wasn't intentionally running it that low; that's just what they were at when I checked it.

I'm about 2,000 miles past my switch from the break-in oil to Mobil 1, and my mileage is pretty stable around 44mpg. I'm interested to see how much the pressure increase helps.

One thing I did notice is that my FAS lengths have increased. I drive over a large hill on the way to work. The "work side" is steeper than the "home side", and I FAS down both of them, shutting off at 60 and turning back on at 50-55 (depending on traffic).

FAS length down the steep side is typically 1.6-1.8 miles. Yesterday I got 1.9, and today I got 2.0 (started earlier). The steep side bottoms out onto a flat, so my speed falls off fairly quickly.

FAS length down the home side is typically 1.2 miles. Last night I went 2.2! (I haven't gone home yet today.) The home side has a longer runout, so my speed falls off more slowly than on the flat. The higher pressure was enough to let me coast well past where I usually have to turn the engine back on. Whee! This means I'm now coasting for over 1/8 of my daily commute!

I'm leaving from Los Angeles tomorrow, driving up the central valley (hwy 99) and over to San Francisco. The last time I made this trip (with break-in oil and normal tire pressure), I managed 47.5 mpg. I'm hoping to break 50 this time.

--Barry

 

Then you will love the FAS at 60psig.