Proposed braking test: comparing tire pressure @ 50 psi vs 35

[vtec-e]

Originally Posted by marinpa

He said this is impossible and very adamant about it, yet he was the one that said he never had the curiosity to test it.

This. Is the one thing that galls me no end.

[marinpa]

Originally Posted by CapriRacer

TD,

Remember me? I'm that guy you are talking about - and I'm sorry, you have once again failed to accurately portray things. I mean things got so bad at that other web site, the moderators had to close the threads!

Please note how many posts I have made on this web site, while I note - at the time I am writing this - you have 3. Also notice how many times I have been thanked for my posts.

You must learn to be more careful about what you say. People may ask you to back up what you say.

Hey CR,

Man it was a pleasure reading your posts and to tell you the truth, I am not afraid to say that, I have learned a thing or two.

I totally do understand your position (social and professional) and I like to believe that whatever you are doing (saying/typing) is in good faith.

But see what a difference between this forum and the other one. Here not only that no one is trying to "chop my head off" for advancing the idea that 50 PSI is not a bad thing, on the contrary they are ok with it, and some of them have already experienced the high pressure inflation.

Where I don't agree with you, and where we have really came toe to toe on the other forum, is that you are dismissive of my experience as professional precision/performance driver, of my 8 years plus of practical experience with more than 200,000 km driven on 10 PSI over the sidewall max on my training vehicles as well as my personal ones.

And what did you say? I quote your exact phrase: "Let’s talk credibility for a moment – as in, you have none."

More over you are dismissive of other 2 master drivers, Sgt. Dave Storton and Bobby Ore that are advocating high PSI, and applying this technique every single day.

For the people do not know who Sgt. Storton and Bobby ore are here is a brief summary:

Sgt. Dave Storton is the Director of the San Jose Police Academy, and he holds a Master's Degree in Adult Education. He is the lead instructor for the Emergency Vehicle Operations Course (EVOC) at the San Jose Police Academy, and is a lead instructor for the local regional academy. He teaches EVOC instructor courses, advanced EVOC instructor courses, off road EVOC, counter-terrorist / dignitary protection driving, and motion picture stunt driving. Dave has trained over 3,500 drivers.


Bobby Ore, a Precision/Performance Master Driver traveled the world for 25 years teaching military, FBI, CIA and Secret Service agents to drive in extreme circumstances.
He holds 13 automotive world records (to date), including one for driving a London double-decker bus on two wheels for 810 feet.

Now what I said then, and what I'll say now too, is that if those kind of people are wrong and they have no idea about driving, tires, safety and vehicle/tire dynamics, well I would rather be wrong too rather than follow urban legends spread, fueled and maintained by groups or individuals with the economical vested interest.

As a tire engineer you might know a lot about tires, but when it comes to driving experience, driving skill and capability....please let others speak.. ..

You are dismissing the hyper inflation like a plague, yet as engineer you said you never had the curiosity to perform any tests, laboratory or driving tests, where the tire will be subjected to regular loads at 50 PSI and see what happens. As well you said the tire industry never performed a a bursting point test. You told me that no one performed those tests because as far as the tire industry is concerned, such tests are not..."relevant"

But for me as the consumer is very, very important to know what is the bursting point of my tires under my vehicle load.

And if on a Crown Victoria with a (static) load of 4000 lbs. the burst point is 250 PSI (on a given tire) there is no reason in hell why I would drive around, as per car manufacturer recommendation, with 32 PSI.

As I said, I have nothing to prove, I have nothing to sale I just want to find out the truth. A truth that oil industry (car/tire/oil producer) is trying to bury it under a bunch of rubbish science or pseudo science and has all the interest to keep the general public uninformed so that they can generate more income.

Because let's be honest, the lesser PSI, the higher the rolling resistance, the bigger the profits for the above mentioned industry.

I told you I am willing to meet with you in person and spend a day or two on a driving pad or race track to experiment and document different PSI settings.

I am willing to drive all he way from Vancouver, BC ( yes on 10 PSI over the sidewall max.) to wherever you want.

You or anyone else for that matter willing to spend a weekend doing some tire tests.

Read the title of this thread: "Proposed braking test: comparing tire pressure @ 50 psi vs 35". That's what made me subscribe to this forum and start to participate.



Regards

[vtec-e]

Marinpa, i wish i could be as well spoken as you are. Good post!
I wholeheartedly disagree with the notion that a high post count equals righteousness or what have you. On a forum in Ireland there is this "guy" that has thousands of posts under his belt but when i looked into them they were literally ALL one or two line posts!
Having said that, Capri Racer is very clued in at his profession and that is to be applauded. However, his quote above, re: having more posts is odd to say the least.
In any case, i would like very much to see scientific tests done on the subject of this thread.
Mythbusters came awfully close to covering it recently but fell short of doing a braking test.
I get the liability issue but seriously, we're all adults and can make our own choices. Anyway, at the start of Jackass or whatever, they tell you "not to try this at home" and thats them covered. So why not braking distance tests on mythbusters then?

We all know the answer to that.

[marinpa]

CapriRacer knows what he knows and he seams to be very knowledgeable in his area of expertise, but so far he couldn't bring and ounce of evidence that driving on 5-10 PSI over the sidewall max. could cause the tire to burst.

Radial tire technology, nowadays encapsulates individual cables of material, bands of steel and synthetic fiber rather than layers of fabric or steel, thus in a tire we have more individual components than in a car engine. So without a proper physical test the experts have an almost impossible task of accurately measuring the basic components, much less figuring out which compounds evolved into what.

Tire engineers can only predict how all the compounds; polymers, sulfur, carbon black, oils, waxes, resins will interact with the structural components. I suspect, but I might be wrong, so please CapriRacer correct me if so, that long after leaving the production lane, the tire will evolve and develop new properties, especially if the tire is overheated.

Unless a physical test, lab or road test would be absolutely impossible to predict in any driving conditions at any pressure (PSI). When I expressed this view, CapriRacer said:
(I quote) "Since you haven't got the fundamentals right, what makes you think you've got a good grip on anything else? Especially when you are talking about areas outside the envelope. I've explained why the burst pressure is not something that has value - except as confirmation that the theory works - and it does. As I pointed out, the company I work for doesn't even do burst testing anymore. They are confident they have a good handle on strength calculation and its affect on fatigue."

When does the overheating occurs? When the tire is underinflated. We will need a tire specialist to come with a complete scientific explanation and mathematical equation and create a mathematical model in order to let us how and why tire overheating occurs, but the common sense and driving experience (and in not so many words) says that overheating occurs (chiefly) due to and increased sidewall flexing.

As a visual example, pull out from your wallet a bank or credit card. Put the card on tall between your thumb and the index (or middle finger) and start to apply pressure.
You will see the card will bend very, very easily. That is more or less what is going on with an underinflated tire.
Do that few thousand times and the card will undoubtedly brake due to a chemical deterioration of the plastic on the bending line.

Now, take the card and places it between the fingers on wide. You will immediately see that you will need to apply much more force in order to bend it, and the bending curve will be much, much smaller. That is (more or less) how a properly inflate (45-50 PSI) tire will behave.

A 45-50 PSI tire inflation can have many names. Some of us will call it properly inflated, some might call it hyper-inflated. The tire industry love to call that grossly and dangerously overinflated.

According to FARS, between 35-38,000 people get killed in traffic crashes and other 5 million are getting hurt in US alone year after year after year, for the past 15 years. MVAs in the USA, Road Traffic Accidents and FARS statistics reveals that over 95% of motor vehicle accidents are caused by driver behavior. Driver distracted by a cell phone call or a spilled cup of coffee, under the influence, inattentiveness, running red lights, falling asleep.etc, etc, etc.

The next most common cause is equipment failure such as loss of brakes, and steering/suspension failure. The least common cause for a equipment failure is tire failures.
All reported equipment failure accounts for less than 5% of all motor vehicle accidents.

The most common tire failure is thread separation caused by uneven or worn-out tires caused by improperly balanced tires, or misaligned or broken suspensions.

On the tire failure list, overinflation is yet to be cited as a sole contributive cause of a car crash.

Maybe someone (CapriRacer?) can point out a statistic in regards to the overinflated tires as a cause of failure.

[marinpa]

Originally Posted by vtec-e

I used to go to 50psi but experienced savage wheel bounce one day when i braked just before a small step on the road surface. All was well until the tire went over the step, which was about 3/4" to 1". Then my front wheels just bounced like crazy and the ABS was going at it like a minigun! I sharted as i continued to "slide" onwards. Dropped to 40psi and it didn't happen. Maybe my shocks are on the way out but they still pass the NCT which is a biannual test on the car to ensure roadworthiness.
Having said all that, there was great grip on smooth surfaces and even wear, once i didn't go sidewall max from new.

My dear friend, most of the symptoms, if not all, are caused by some underlying mechanical problems.

The bouncing wheel feeling is a result of a mechanical cause known as "bump steer" and it might be caused by upper/lower arms and or ball joints, upper arms shims. Check the nuts on the upper control arms, make sure they have not backed out.

As try to determine if you are dealing with a bump steer where both wheels rise together or a roll steer where a wheel rises and the other falls.

By lowering the PSI in your tires you did not addressed the mechanical problem but applied a quick fix and make the front end steering less crisp, hence less responsive.

[vtec-e]

I'm due a clutch so i might just get the shocks done while she's up on the hoist.
Regarding loose nuts, i don't think anything is loose so it may well be the shocks. I'm a maintenance technician so i'm always listening for new rattles to fix!

Oh, and when it comes to getting flamed when overinflated tyres are mentioned, i got that t-shirt too! I was a member in an astronomy/space travel forum and there was a general science forum within it. There were guys in there that could calculate how much fuel would be required to send the ISS around the moon and back. So, i figured these fine people could shed some light on the subject of grip vs tyre pressure.

Well, i got one or two "maybe there's something in it alright" kind of posts and then it got ugly. Not once was there a calculation thrown about and after i was repeatedly told i would wear the centre more i had to post a picture of one of my tyres with 100,000km on it and EVEN wear, which was about 4mm at that point! A few mumbles and grumbles later and the thread died. I finished off by saying how disappointed i was to get such abuse from supposed scientists. I kind of expected not to get proper scientific analysis on the subject but i wanted to see it unfold anyway, just to reinforce my belief that there is a conspiracy in force, with respect to tyre pressure and grip etc.

[redpoint5]

So, 5 pages into a request for empirical evidence, and this thread is no different than any other tire inflation thread; how disappointing.

I have learned some neat things regarding inflation for maximum cornering though. It would be neat to see someone do a braking test and compare it to the cornering test to see how closely the 2 optimal PSI figures come.

[marinpa]

Originally Posted by vtec-e

I'm due a clutch so i might just get the shocks done while she's up on the hoist.
Regarding loose nuts, i don't think anything is loose so it may well be the shocks. I'm a maintenance technician so i'm always listening for new rattles to fix!

Oh, and when it comes to getting flamed when overinflated tyres are mentioned, i got that t-shirt too! I was a member in an astronomy/space travel forum and there was a general science forum within it. There were guys in there that could calculate how much fuel would be required to send the ISS around the moon and back. So, i figured these fine people could shed some light on the subject of grip vs tyre pressure.

Well, i got one or two "maybe there's something in it alright" kind of posts and then it got ugly. Not once was there a calculation thrown about and after i was repeatedly told i would wear the centre more i had to post a picture of one of my tyres with 100,000km on it and EVEN wear, which was about 4mm at that point! A few mumbles and grumbles later and the thread died. I finished off by saying how disappointed i was to get such abuse from supposed scientists. I kind of expected not to get proper scientific analysis on the subject but i wanted to see it unfold anyway, just to reinforce my belief that there is a conspiracy in force, with respect to tyre pressure and grip etc.

As far as I am concerned the only time tires are wearing in the center is when ratio tire/rim does not match (oversized tire/narrow rim).

Unless a such mismatched combination, I have a very, very hard time to believe that a passenger tire can retain a convex (egg shape) form after applying a constant loading force of 4-500 kg.



I haven't seen that shape no even on an unloaded tire inflated at 50 PSI.
All the images showing a convex form of a tire are drawings such as this



But even in this image, the presenter fails to show me the egg shape form.

That does mean I might not be wrong. If there is any tire specialist that can show me images of an egg shape passenger tire, I'll be more than happy to apologize.

[marinpa]

Originally Posted by redpoint5

So, 5 pages into a request for empirical evidence, and this thread is no different than any other tire inflation thread; how disappointing.

I have learned some neat things regarding inflation for maximum cornering though. It would be neat to see someone do a braking test and compare it to the cornering test to see how closely the 2 optimal PSI figures come.

You do understand that a such test would require time, money and effort.
Those are resources, commodities like, and most of the people would like to invest them on children, family and friends, job/business, etc.

In order to be a relevant and credible evidence, the test would need to be reasonable in nature, documented in detail and make it replicable. As well will have to be performed on standards that would make it available for screening.

The trickiest part (time and money consuming) would be documenting it, namely video recording. Taking the video, downloading it to your computer, editing, converting, uploading it, etc, etc requires ample time and some specialized skills that most people simply do not have.

All that time and effort (and money) would exceed the scope of this conversation/thread.

Second, no test in which you are not a direct participating would be relevant (for yourself).

I, for one, would love to form a group, and in one weekend, sometime this summer, to orchestrate our efforts, meet somewhere and perform the tests.

How does this sound to you?

[euromodder]

Originally Posted by vtec-e

In any case, i would like very much to see scientific tests done on the subject of this thread.

Not very scientific, but here goes.
I've noticed huge difference between different tyres, and smaller differences due to the condition of the brake pads, but I have not found any problem or noted change with the braking power of the tyres due to pressure.

Between 36 and 51 psi, they stop the car just as well.
Or equally bad, as they are dedicated LRR tyres.


Your Yaris is lightweight, so if the shocks are getting worn out, that'll only increase the bounciness as the shocks can't cope.

BTW: I once had a Yaris 1.4D with 185/?/14" wheels and Michelin Pilot Exalto 2 tyres.
That thing stopped as if it ran into a brick wall.
It also used more diesel than my Volvo does now