Fill to vehicle spec or tire spec?

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Originally Posted By: TacticalDriver
Originally Posted By: Astro14

Tactical Driver is advocating extreme pressures for extreme usage...


C'mon you guys.. .. 5-10 PSI over the sidewall Max PSI is not..."EXTREME".



I could imagine someone advocating 5-10 above vehicle placard pressures (which is not to say I'd agree with that) but 5-10 above SIDEWALL MAX pressures? Get real.

My vehicle recommends 29F/33R for normal loads up to 4 persons (which I have adjusted up 3-5 psi depending on the exact tires installed and load conditions) and 33F/41R for max vehicle load (5 persons plus luggage and roof rack).

My sidewall max is 51psi IIRC so you're advocating that I go out and fill to 61F/61R (vs. 29/33) because you're smarter than everyone else, including both BMW and Michelin?

mmmkay...

My excellent fuel economy, good handling and perfectly acceptable tire wear (for tires rated around 200 UTQG) are probably all part of the "conspiracy" too, right?
 
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Yeah...I was thinking I should ignore my experience, vehicle and manufacturer's recommendations, and crank up the pressure on my compressor so I can inflate all my tires up to roughly DOUBLE where they are...

Then, I will ignore the vehicle manufacturer's recommendation when I get back into the cockpit, and exceed all the published limits because I know better than the engineers who designed it...

Want to ride in back?
 
Originally Posted By: TacticalDriver

Meaning I am only going to tell you half of the truth.


What do you expect him to do? Go against his company policies and get fired and/or sued for divulging proprietary information? The guy does the best he can given his position. He's been on here much longer than you have, and I have never seen him take sides. He's as objective as they come when it comes to tires and wheels. But that's just my opinion. You certainly have yours. That's fine.
 
Originally Posted By: TacticalDriver

Handling related to the tire pressure
http://www.youtube.com/watch?v=5r6gV2JWI0I

This video shows two pressures, properly inflated at 36PSI and much under-inflated at 15PSI.

I'm interested in a test comparing placard pressure, 2-6 PSI above placard pressure and max pressure on sidewall. My guess, the max performance/handling is with 2-6 PSI above placard pressure.
 
Originally Posted By: HTSS_TR
Originally Posted By: TacticalDriver

Handling related to the tire pressure
http://www.youtube.com/watch?v=5r6gV2JWI0I

This video shows two pressures, properly inflated at 36PSI and much under-inflated at 15PSI.

I'm interested in a test comparing placard pressure, 2-6 PSI above placard pressure and max pressure on sidewall. My guess, the max performance/handling is with 2-6 PSI above placard pressure.


I would be interested in some more data points, including cars with 35-40 series tires, like an BMW M-series, or a Porsche, and then the big boats, like a Crown vic, with 70+ series tires...

I suspect that the cars that came with 35 series have recommendations pretty close to optimum for handling, while the 70 series is optimised for ride. While the 70 series may handle better by going a bit over vehicle placard, I doubt the high-peformance car would....

The problem with the anecdotal evidence provide by Tactical Driver is that it's on one type of vehicle, which is not extensible to all vehicles...there are too many variables...
 
Originally Posted By: Craig in Canada
Originally Posted By: TacticalDriver
Originally Posted By: Astro14

Tactical Driver is advocating extreme pressures for extreme usage...


C'mon you guys.. .. 5-10 PSI over the sidewall Max PSI is not..."EXTREME".



I could imagine someone advocating 5-10 above vehicle placard pressures (which is not to say I'd agree with that) but 5-10 above SIDEWALL MAX pressures? Get real.

My vehicle recommends 29F/33R for normal loads up to 4 persons (which I have adjusted up 3-5 psi depending on the exact tires installed and load conditions) and 33F/41R for max vehicle load (5 persons plus luggage and roof rack).

My sidewall max is 51psi IIRC so you're advocating that I go out and fill to 61F/61R (vs. 29/33) because you're smarter than everyone else, including both BMW and Michelin?

mmmkay...

My excellent fuel economy, good handling and perfectly acceptable tire wear (for tires rated around 200 UTQG) are probably all part of the "conspiracy" too, right?



My friend, I am talking from own perspective and own experience. I am using this technique for 8 years, more than 200,000 km driven, on my training vehicles as well as my personal ones, I know a number of LEA (law enforcement agencies)using it.

Two of the people advocating 5-10 PSI is Sgt. Dave Storton, 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.

The other one is 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 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.
 
Originally Posted By: Astro14

The problem with the anecdotal evidence provide by Tactical Driver is that it's on one type of vehicle, which is not extensible to all vehicles...there are too many variables...


My friend, vehicle and tire dynamics are governed by the same set of physics laws of motion, regardless we are talking a Mini Cooper, a Crown Vic, an armored truck, a 18 wheelers, a train, a motorcycle or a horse carriage.

95% of the drivers are either oblivious, ignoring or omitting the vehicle dynamics, due to the fact that math and physics are required. For most of the people their only exposure to the laws of physics was in high school, where the subject does not go beyond the class room and often times seems to have no practical value.
 
Originally Posted By: HTSS_TR
Originally Posted By: TacticalDriver

Handling related to the tire pressure
http://www.youtube.com/watch?v=5r6gV2JWI0I

This video shows two pressures, properly inflated at 36PSI and much under-inflated at 15PSI.

I'm interested in a test comparing placard pressure, 2-6 PSI above placard pressure and max pressure on sidewall. My guess, the max performance/handling is with 2-6 PSI above placard pressure.


My point with that video clip is; Why tire manufacturer don't conduct such experiments. where they can rig a wide array of electronic equipment measuring objectively the data take from a vehicle, driving the same course at the same rate of speed but with various PSI settings.

The measuring technology is in place, they have a lot of technicians and engineers, they have space and time.. ... why don't they do it?

Chances are they already did those kind of tests but do not want to share the results with us because then we will spend less and less money on tires and gas.

CapriRacer just said something to the extent of.. .. "what's the point of testing or finding out what is the bursting point of a tire" (or something like that)
 
Originally Posted By: IndyIan

As for your "fill near bursting is best" theory, go do some testing yourself. "


Pardon the interruption.. .. but who said filling the tire near to the bursting point?!?!?

The bursting point is over 200 PSI. I was talking about 25% of that.
 
Originally Posted By: Craig in Canada

My excellent fuel economy, good handling and perfectly acceptable tire wear (for tires rated around 200 UTQG) are probably all part of the "conspiracy" too, right?


Excellent fuel economy compared with what? According to who?

Did you have the curiosity to experiment and document different PSI settings? Did you drive around the track 4-500 miles with each setting and reach the conclusion that the manufactory recommended setting (placard) gives you the best traction, stability, fuel economy and the most optimal tire wear and tear?

According to one of very few tire specialist in this forum, the current tire load tables standards for the passenger vehicles is dating 1970. So...unless you did not change the tires since 1970, it would be fair to assume that your 29F/33R
recommendation is based on a 40 years old methodology.
 
Originally Posted By: TacticalDriver
Originally Posted By: HTSS_TR
Originally Posted By: TacticalDriver

Handling related to the tire pressure
http://www.youtube.com/watch?v=5r6gV2JWI0I

This video shows two pressures, properly inflated at 36PSI and much under-inflated at 15PSI.

I'm interested in a test comparing placard pressure, 2-6 PSI above placard pressure and max pressure on sidewall. My guess, the max performance/handling is with 2-6 PSI above placard pressure.


My point with that video clip is; Why tire manufacturer don't conduct such experiments. where they can rig a wide array of electronic equipment measuring objectively the data take from a vehicle, driving the same course at the same rate of speed but with various PSI settings.

The measuring technology is in place, they have a lot of technicians and engineers, they have space and time.. ... why don't they do it?

Chances are they already did those kind of tests but do not want to share the results with us because then we will spend less and less money on tires and gas.

I believe they test various pressures and the recommended pressure is a compromise of ride, performance and fuel economy. Someone like myself like a firmer ride and better/quicker steering respond so that I inflate the pressure up between 4-6 PSI.
 
Originally Posted By: Quattro Pete
Originally Posted By: TacticalDriver
but according to CapriRacer this is a truck tire with a 90 PSI tire wall max pressure
http://www.youtube.com/watch?v=HiLeji8bLOk

You seriously can't make out it's a truck tire just by looking at it? When was the last time you've seen a tire and rim of this shape on a passenger car?



Seriously I can not make out the type, size and tire wall max PSI. I am not a tire specialist remember?
 
Surely someone with such keen observation and insight has seen that type of assembly somewhere on the road.

I've not seen many non-commercial vehicle applications with 8 studs holding the wheel on.

tyre.jpg
 
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Originally Posted By: TacticalDriver
Originally Posted By: CapriRacer

Burst data? You won’t find that published anywhere. Why would anyone want to know what the burst pressure is if they are using pressures well away from the burst pressure? – and if they aren’t, then they will have to accept the results of that decision.


Ha, ha, ha!!!!! That's so mean! We need to know the exact burst point and from there work our way up with the calculations and find a happy median between safety/traction/consumption (fuel economy)/usage depreciation

This i a very common practice called Ultimate Tensile Strength
where the engineers can figure out what is the maximum stress point a material can withstand while being stretched or pulled before.

The testing involves taking a sample of material and in a controlled environment increase applied force until the sample changes shape or breaks.


And you know what ?

NOBODY designs or tests ANYTHING based on the UTS of the material that they intend to use either to hold stuff up, hold pressure in, or stop spinning things from flying apart.

As you would be well aware, the fatigue limit for a material is many times lower than the UTS, and many materials don't even have a fatigue limit, requiring an even higher factor of safety.

UTS tells you nothing about how a pressure vessel will respond to temperature and pressure fluctuations (thermal and mechanical), manufacturing processes, material degradation and manufacturing flaws.

Pressure vessels (and a tyre is one) are manufactured to a design pressure, tested to a (static) test pressure, and never in my experience been purposely tested to destruction , as it's of absolutely no relevance to operating pressure equipment.

The receiver on your shop compressor has a "Safe Working Pressure", that is lower than the design and test pressures....therefore it has a "Factor of Safety",and in pressure equipment design, it's usually pretty substantial (I know because I've designed stuff for 1000F and 2600psi).

Are you safe operating beyond the Safe Working Pressure ?

Undoubtedly...but you,not being the designer never know HOW the vessel was designed,and where in the range you are operating.

But if something happens,and you have been outside the envelope, you'll need a really good lawyer.
 
Originally Posted By: Astro14
To claim that increased inflation pressure (which reduces the footprint/contact patch - that's basic physics) results in increased traction is simply not true. You may get better steering response or cornering(in some specific cases) because of a more stable contact patch, but you have reduced the contact patch, and it is the interaction of the tire compound with the road surface that yields grip. That's why racing slicks have more traction (dry) than all-season/rain tires. I suspect that increasing pressure works well on a Crown Vic or Suburban that wasn't intended for tracking, but there are better methods for a Porsche or other sports car that was intended for that use.


From "How to Make Your Car Handle", the premise is that there's an "optimum" pressure for grip, and they tyre behaves more negatively to underinflation than overinflation...i.e. as you increase pressure to optimum, you see marked difference,but once optimum is reached, overinflation displays less of an effect...but overinflation is still sub-optimal.
 
To All,
In my opinion an expert who cannot reveal his expertise to others, for whatever reason, is an expert to his own benefit only.
Hence, I will weigh, observe, and put into practice those things which work for me.
This subject is not for the masses. They cannot comprehend the possible benefits.
Jim
PS Tactical Driver is following a path which has been long established and proven. The experts could they agree, would.
I have followed that path for a time, and will not turn back to the way of the blind masses.
Have a good day all.
 
CapriRacer speaking of the http://www.barrystiretech.com/ website, I hope you realize that these so called 50 psi tires could have been labeled 35 psi tires.
See "notes on page 1-34".

That Tire and Rim Association paper is listing the MINIMUM pressures for each load. MINIMUM. Then in a note on the very next page it states this:



"Cold inflation pressures may be increased above those applicable to the tire loads up to the maximum marked on the tire with no increase in load."
In other words up to max sidewall is perfectly safe.

Black and White from the Tire and Rim Association.
 
But you are advocating operating ABOVE that safe Max aren't you ?

i.e. in the uncharted area of the safety factor.
 
Originally Posted By: Shannow
But you are advocating operating ABOVE that safe Max aren't you ?

i.e. in the uncharted area of the safety factor.


What is the Safety Factor?

Jim
 
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