15 more PSI = 7% better MPG

[cbaber]

Enough with the theories, this is credible evidence. You may need to zoom in to read the graphs. Press CTRL and the + button to zoom in, and CTRL and - key to zoom out.

Barry's Tire Tech

I'll highlight a few important points.

I hope you noticed how flat the wear index is for the radial tire. I interpret this to mean that conducting a "chalk test" is not a good way to determine what the best pressure is for wear. Put another way - Radial tires are pretty insensitive to pressure when it comes to wear pattern.

The first parameter they looked at was cornering coefficient - and all that yielded was that increasing pressure resulted in a quicker responding tire

Braking Traction: Dry traction is unaffected by inflation pressure, and while wet traction is improved, the effect is small.

Dynamic Bruise: More pressure is worse.

[qx4dude]

Originally Posted by cbaber

Enough with the theories, this is credible evidence. You may need to zoom in to read the graphs. Press CTRL and the + button to zoom in, and CTRL and - key to zoom out.

Barry's Tire Tech

I'll highlight a few important points.

...But you neglected to highlight another important point:

"But on a whole, this paper seems to point towards increasing inflation pressure is better for many properties, the effects are fairly small, and the ones that aren't better might be compensated for by changes in the vehicle suspension. The only thing that points towards a significant safety issue is the plunger energy - and while this is a relatively rare occurrence, the results of a tire failure due to an impact can be quite severe. I wish there were better statistics on accidents involving impacts so this could be better assessed."

I'm not sure how "credible" this evidence is since the paper was written more than three decades ago - but you found vindication because it tends to support your argument.

I'm sure I could request (current) test data from all of the major tire manufacturers, auto makers, government agencies, etc, and post it here to support the over-max-sidewall-PSI is unsafe argument - but honestly, it wouldn't make any difference. You (and apparently most others here) have concluded that it's perfectly safe exceed max sidewall ratings at will. If the data supports your argument - it's the gospel truth. If it's contradictory, then there must be a hidden agenda, or a conspiracy. Like I said before, it's a free country. What you choose to believe is none of my business. I'll just go back to my first point: Before advocating the wonders of running passenger tires at 60, 80, or higher PSI - readers need to be told that it "could" be dangerous, and to do so at their own risk.

At this point, let's just agree to disagree. We've beaten this thing to death.

[niky]

I combed for weeks last year looking for resources for a seminar we held then.

None of the modern published papers actually show that. All of them show that less pressure is more dangerous.

[euromodder]

Originally Posted by qx4dude

The cavalier attitude about exceeding "max sidewall" pressure is astounding. Teams of engineers at major tire manufacturers have worked with teams of engineers at auto makers to determine the maximum safe tire pressure

They probably found it to be so high the lawyers wouldn't allow them to use it

I'll admit that I have raised pressure in my tires 6 PSI over the door sticker's recommended 36 PSI (which has improved FE), but I won't go anywhere near the stated maximum 51 PSI sidewall pressure. I'll put my trust in the engineering team that designed the tire over an anonymous Internet user's "research".

So you DON'T trust the engineering team after all ?
They tested the tyres @ 51 psi - and with a considerable safety margin.

[CapriRacer]

I'm combining a number of responses in one thread. I hope ya'll don't mind.

One comment before I proceed: I am glad this thread hasn't degraded into a shouting match. That is never productive. I think it is important that we try to understand the way things work and leave our sensitivities behind. We can deal with them later.

Originally Posted by cbaber

Enough with the theories, this is credible evidence. You may need to zoom in to read the graphs. Press CTRL and the + button to zoom in, and CTRL and - key to zoom out.

Barry's Tire Tech

I'll highlight a few important points.

I looked at this paper intensely - and there were a number of things that jumped out at me.

First was that the paper didn't describe a lot of the testing. I think that is important because some tests are designed to look at one kind of phenomenon and aren't suitable for looking at another.

A good example of this would be wear testing. There are some tire wear tests that are designed to give an indication of how long it takes a tire to wear out. THAT test tries to avoid those things that cause uneven wear, since that would invalidate the test results. Other tests are specifically designed to emphasize un-even wear.

I get the impression that the wear test conducted in that paper was the former and not the latter, so I wonder how valid the results are. I have similar concerns about some of the other testing as well. More importantly, there have been many reports of center wear when using high inflation pressures and that contradicts this paper. Without being able to explain why we are getting these reports, the test data is just interesting but doesn't seem to match real life experiences.

Originally Posted by qx4dude

.......On a mass-produced vehicle like that, how much would it really cost on a per-unit basis to make the suspension a little softer so that an extra 10 PSI goes unnoticed by the new car buyer?.....

I think this is the crux of the problem: Tweaking the suspension doesn't compensate for the added 10 psi - or put a different way: If it were that easy, they would have already done it.

Originally Posted by euromodder

......So you DON'T trust the engineering team after all ?
They tested the tyres @ 51 psi - and with a considerable safety margin.

Ah..... That's not exactly true. It's true that SOMETIMES tires are tested at 51 psi - BUT - it is NOT related to what is stamped on the sidewall of the tire. It is related to the speed rating - AND even then, it's only for that one test.

[gone7]

Originally Posted by cbaber

I'm not arguing against science when I say higher pressures are fine. There hasn't been one piece of credible evidence posted that suggests over-inflating a tire can lead to the horrible things mentioned in this thread. Quoting tire information from a tire manufacturer is not science. I want to see the raw data.

You may choose to blindly accept factory recommendations, but I don't. Not when I have seen so many veteran members have success with over-inflation. As I have said many times already, I'll report my success and my failures.

You haven't given any science. You just ignorantly claim that people who follow engineering recommendations are blind. Now that's ignorant.

And until you run a new set of tires until they wear out, you have nothing, and neither does any one else.

[gone7]

To Everyone:
Please note that this topic is not about under-inflation. It is only about over-inflation. Let's not confuse the issue any longer by mentioning somethng that is clearly off-topic and non-applicable.

[qx4dude]

Originally Posted by niky

I combed for weeks last year looking for resources for a seminar we held then.

None of the modern published papers actually show that. All of them show that less pressure is more dangerous.

I believe extremes are usually dangerous. It's like going to the doctor, and getting a prescription for blood pressure pills. The bottle says take one tablet twice daily - USE AS DIRECTED.

Doctors and pharmacists went to school for at 8 years (and longer) to be able to practice, and dispense medicine. Most high blood pressure patients will heed the warning label. Others will do their own "experimenting" with the dosage. That's what's happening here with with this under and over inflation debate. Why people don't just stay within established parameters is beyond me. If the tire manufacturer states a "maximum" and the auto maker has a "recommended minimum" PSI - just pick something in between to suit your taste.

There are warning labels on almost everything we use. I generally believe they are put there for our own safety - and to protect the manufacturer from people that don't take them seriously.

[mcrews]

Please....stop.
Over the counter meds come with an expiration date which is totally bogus. ( I worked in the industry for 10 yrs)

[cbaber]

Originally Posted by ACEV

You haven't given any science. You just ignorantly claim that people who follow engineering recommendations are blind. Now that's ignorant.

And until you run a new set of tires until they wear out, you have nothing, and neither does any one else.

Do you really believe they are engineering claims? Or are they risk management claims? Don't you think it's odd that no matter which tire manufacturer you choose, the max PSI is 35, 44, or 51 depending on size and tire type? Look on YouTube and you can find video's of people that try to blow up tires. It always takes at least 150 PSI unless the tire/wheel is already damaged. This shows you just how much structurally the tires can handle. That number is significantly lowered when you add in the load of the car, plus the heat from driving. And I clearly stated in my previous post that over inflated tires have less puncture resistance.

I'm considering doing a chalk test I found online. Apparently the 4x4 guys use it with their offroad tires to find the correct PSI. It consists of applying chalk to the tire surface and then driving a few hundred hards in a straight line. Any major uneven wear shows up when the chalk is not evenly faded.