Hyperinflating tires

[MazdaMatt]

If my life was not already scheduled to a full 30 hours per day, I would love to run a full magazine-style scientific comparison test between 3 settings.
0 camber, 32psi
0 camber, 60psi
1* camber, 42psi

Testing each one for rolling resistance, highway 70-0 stopping distance dry and wet, cornering g-load dry and wet, tire temperature distribution for each of the above.

I could speculate that a person that does mostly highway driving, in a VERY safe (no drafting, eyes up) manner would get the best mileage out of 0/60, but best tire wear pattern, cornering and braking out of 0/32. And I would speculate that a mostly city driving hypermiler would get the best of ALL factors at 1/42. Again... this is technique, climate, weather, vehicle, tire, road surface etc dependant.... and total speculation.

My reason for speculating 42psi for best mileage for a city driver is a) an assumption that RR is not massively reduced from 42 to 60 and b) that significantly higher cornering speeds could be acheived with the lower pressure and negative camber.

[trikkonceptz]

Like I have said before, I have seen a report posted here from 1980, regarding the issue and just read alot of speculation.

My fact remains that I currently have new tires on my vehicle that have been overinflated since day one. 55psi to be exact. 30K miles later, it has exceeded the life of the previous set and still look new.

I have seen and experienced better dry road and wet weather handling and I drive in a brutal enviroment, all highway with road surface temperatures exceeding 130 degrees F.

Other than a rougher ride I wish I had done this sooner.

I think we need to just acknowledge that there is a benefit to practicing this with no long term data to support danger to occupants or vehicle and say it is not encouraged so practice at your own risk. Because there will be no one that can step up to answer the question directly since no testing is done with tires at these pressures.

[KJSatz]

I am sorry if everyone's already seen this link, but it basically advocates always inflating to the sidewall max (for police officers, but whatever). I'll go to the gas station next Saturday and fill my tires up to 40psi now that I read this (yesterday I filled up and inflated my tires to 35psi).

http://www.officer.com/web/online/Editorial-and-Features/Driving-Under-Pressure/19$27281

[whitevette]

Originally Posted by aerohead

I saw this discussion last week and have been looking at some of my old articles and SAE stuff.-------------The nuts and bolts of it seems to be that you don't exceed the max. rated pressure embossed on the sidewall of the tire.---over-inflating the tires beyond recommended pressures will reward you with no measurable improvement in mpg.


Factory pressures are set for braking bias,and determine whether the car will oversteer or understeer,once the limits of adhesion are reached.Carmakers like cars to break loose at the front first,then a simple steering input can restore direction.Altering pressures with indescretion could allow the car to swap ends violently ,when pushed in an emergency maneuver.Please don't gamble with your lives for the sake of a liter or gallon of fuel.

"...seems to be..."? How concrete is this? "Over-inflating the tires beyond recommended pressures ... no measurable improvement in MPG (sic)." I do not know what planet you live on, sir ... but in my neck of the woods, your words carry no weight. Any IMSA person ( myself included) knows to the contrary.
Tire science is surrounded by half-truths and legend. If one but "follows the money", they will clearly see the tire industry is fiercely competitive...and the gaining of sales contracts is the life-blood of this industry. So ... given these parameters, can we safely say the industry does not want to endorse the raising of cold pressures ... which will increase the life of the tire ( as well as improve handling and traction)? After all, replacement tires fuel the industry.
And who is gambling with their life for the sake of a gallon of fuel? I thought you just stated there was no measurable improvement in MPG? Now you're talking "a voilent end-swapper" if you change the pressures. This is fear tactics....
The truth is : traction is improved markedly with a small (reasonable) increase in tire pressure, firming the foundation carcass rubber ( reducing tread squirm). Reducing tread squirm cools the rubber and lengthens tread life.
Cars which "break loose" at the front first (understeer) are more forgiving...mushy... and cars which "break loose" at the rear ( oversteer) need to be "steered" with the counter-steer / throttle / hand brake. With the majority of drivers on the road being virtual idiots under either condition...does it really matter about tire pressure bias? "They" lock 'em & hang on!
I'll stop now. Have a nice day.... -Ted Hart / ex-IMSA / Z twist, S twist

[1.5Ldave]

Originally Posted by whitevette

"...seems to be..."? How concrete is this? "Over-inflating the tires beyond recommended pressures ... no measurable improvement in MPG (sic)." I do not know what planet you live on, sir ... but in my neck of the woods, your words carry no weight. Any IMSA person ( myself included) knows to the contrary.
Tire science is surrounded by half-truths and legend. If one but "follows the money", they will clearly see the tire industry is fiercely competitive...and the gaining of sales contracts is the life-blood of this industry. So ... given these parameters, can we safely say the industry does not want to endorse the raising of cold pressures ... which will increase the life of the tire ( as well as improve handling and traction)? After all, replacement tires fuel the industry.
And who is gambling with their life for the sake of a gallon of fuel? I thought you just stated there was no measurable improvement in MPG? Now you're talking "a voilent end-swapper" if you change the pressures. This is fear tactics....
The truth is : traction is improved markedly with a small (reasonable) increase in tire pressure, firming the foundation carcass rubber ( reducing tread squirm). Reducing tread squirm cools the rubber and lengthens tread life.
Cars which "break loose" at the front first (understeer) are more forgiving...mushy... and cars which "break loose" at the rear ( oversteer) need to be "steered" with the counter-steer / throttle / hand brake. With the majority of drivers on the road being virtual idiots under either condition...does it really matter about tire pressure bias? "They" lock 'em & hang on!
I'll stop now. Have a nice day.... -Ted Hart / ex-IMSA / Z twist, S twist

Traction and handling are not the same thing, traction will usually decrease with more pressure, and increase with more footprint gained by lower pressure. drag slicks usually only use 7-10 psi, and when offroad a lot of trail guys drop down to the teens.

Handling reponse is improved with more pressure though, auto cross and road track cars usually have a higher pressure for better steering control and more road feel.

[cookie96civic]

I have the best cooper tires available in sizes for civic dx96, the guy told me they wouldnt burst til about 70-80 psi. He also knows what I'm doing (hypermiling), and said 40-45 is fine for summer, but to drop it back in the winter for better traction. I'm running them at 45, and the eoc difference is visibly noticable. Where i used to come to a stop, bump starting at 20 in 3rd I have to substantially brake harder towards the stop sign or start the eoc much earlier. One EOC that I do which used to last .8 miles, is now almost 1.2 miles, so I can start about 5 MPH slower without blowing the red light. With adding P&G to the mix and knocking some weight off the car, I have seen an incredible increase in MPG. Check my chart on the last 2 fill ups, roughly 4-5 MPG. I'm tired of typing.

[cookie96civic]

He also said as long as he maintains the pressure in the tires, he will continue to warranty them if an issue arises.

[tasdrouille]

Originally Posted by cookie96civic

[...]the guy told me they wouldnt burst til about 70-80 psi[...]

I would absolutely LOVE to see someone take an old wheel and pump the tire till it bursts. What I read in the past lead me to believe it would not burst below 150 psi.

Anyone got an old wheel in his backyard, a compressor with a pretty long hose, and some place to take cover? (That could turn into a redneck's "watch this" so play it safe)

[CapriRacer]

Originally Posted by tasdrouille

I would absolutely LOVE to see someone take an old wheel and pump the tire till it bursts. What I read in the past lead me to believe it would not burst below 150 psi.

Anyone got an old wheel in his backyard, a compressor with a pretty long hose, and some place to take cover? (That could turn into a redneck's "watch this" so play it safe)

If anyone does this, I would suggest they record the tire size and design, the load and inflation information on the sidewall of the tire, plus the DOT number - and pay close attention to the date coding. I've seen very old tires (I'm talking decades old) come apart at 35 psi.

Also, I would suggest anyone who does this view some of the Youtube videos where others have burst tires to get a feel about how violent a tire burst can be.

[bikin' Ed]

Years ago, when employed by a certain US tire maker headquartered in Akron, OH, I was told that passenger tires had to be able to withstand 15% mor load and 15% more pressure than what is posted on the sidewall. This was not the manufacturer's, but rather DOT"s testing requirement. Based on that info I have always pumped my tires to the max on the sidewall.