"Inflation pressure does not affect grip": Autospeed article.

[orange4boy]

Shouldn't tire wear be a factor as well?

For instance the 4 tires on my jeep are about 1000 dollars a set.

I know that on other all terrain tires over inflation
will grind the center away...

You don't know that, you think that. It's not true. Bias ply tires could do this but steel belted radials do not. Steel belts and carcass design help to keep the tread patch flat. Many ecomodders have shown their tires after years of service at high pressure without the centre wearing out first. Higher pressure increases tread life.

[CapriRacer]

Here’s the problem I have with Sgt. Storton’s article:

1) “…..The reason the owner’s manual lists 35 psi is because we get the same manual as the civilian version of the Crown Victoria. The police version, however, is fully loaded with communications equipment, a cage, and your gear. You are not looking for a soft and cushy ride, you want performance…..”

Sorry, but the civilian version does indeed have a different inflation pressure than the police version – and the police version has more . Obviously, the folks at Ford did compensate for the additional weight that is going to be carried by a cruiser.

2) “…..The proper tire pressure for the Police Crown Victoria is 44 psi. If you look on the sidewall of the tire, you will see that it lists 44 psi max pressure….”

Yes, it lists the MAXIMUM pressure as 44 psi, but it does not list a RECOMMENDED pressure. Sgt Storton doesn’t explain HOW he arrived at the 44 psi value.

But later versions of the tire supplied to the Police Pursuit versions of the Crown Victoria have tires where the sidewall lists 51 psi as the maximum, so what about that?

3) “… The tires will not balloon out creating a peak in the center portion of the tread when tire pressure is above 35 psi. There is a steel belt that prevents this from happening….”

Sorry, but the steel belts are neither radial nor circumferential. They are at about a 15° angle. And while the belt slows the “arching” affect down, it does not prevent it from happening.

I am not even going to go into the issue of the “Stunts” involving Ranger pickups.

I think the reason this article has been pulled is that it is full of misconceptions and does not back up the things that are put forth as “facts”.

[rmay635703]

Originally Posted by CapriRacer

Aren't there a number of different questions on the table?

1) Does the size of a tire's footprint affect grip?

Rather pointless to argue over whats known, the footprint affects grip when the surface is not solid like blacktop or cement, AKA sand, snow etc. It can increase grip if it "cuts" through snow/water to a hard surface. It can decrease grip if it doesn't "grab" enough free material like snow or mud.

Originally Posted by CapriRacer

2) Does inflation pressure affect a tire's grip?

These may appear to be the same question, but asked in a different way, but I think you'll find they have some interestingly different aspects that bear exploration.

It can affect the geometry of how the tire distorts, again whether this is good or bad depends on application.

Originally Posted by CapriRacer

Lastly,

3) Friction theory: Do tires behave according to classical fiction theory, where F = µN, nad where µ has a lower value for sliding friction than for static friction.

So which question are we trying to answer?

It isn't so much the tire as the surface you are driving on as alluded to in #1

My take is that if you know the behavior of your tires at a certain pressure (mine are at 60psi) and drive responsibly (and have the experience to do so) This conversation is likely irrelevant.

In the 1,000,000+ miles I've driven I have never had a blowout (or an accident above 5mph), I have had a tire punctured twice (both in gravel lots by glass or nails) and I have had the valve stem regulator removed as a prank by some arse wipe. Except for those on the suburban most tires have exceeded their rated lifespan and usually fail because they become unbalanced or undulated in the sidewall or the tread quite late in the game mind you.

As for handling terrain on road, I have never "lost control" on any public road at speeds above 5mph. I believe knowing your vehicle is much more important than the tires you are using or the pressure they are at, and obviously you can adjust your tire pressure if conditions are bad, not like it takes all day to do.

Only had trouble stopping once and that was because my rear brakes became inop on wet leaves which resulted in a 2mph collision and no damage.

The main issues with excessive pressure is excessive wear to your suspension, there are definately places you DO NOT WANT too much pressure and you do have to avoid certain obstacles you may otherwise ignore. The 2ft deep potholes around here are murder.

[orange4boy]

I think the reason this article has been pulled is that it is full of misconceptions and does not back up the things that are put forth as “facts”.

The article is obviously an informed opinion and presented as such.

At the beginning of the tread is a list of documents supporting my points. Perhaps you should read them.

Even the NHSTA thinks over inflation is not a safety issue.

Sorry, but the steel belts are neither radial nor circumferential. They are at about a 15° angle. And while the belt slows the “arching” affect down, it does not prevent it from happening.

That's true, I'll point hat out in the article. Nevertheless, tires inflated to max sidewall do not wear out faster in the centre in my and many other's experience.

We have posted the best information we can find including studies but I still have not seen a study giving solid evidence of danger, reduced traction, increased wear or most of the other myths trotted out about max inflation. PERIOD. Find them and post them if you can. I am open to it.

[orange4boy]

Originally Posted by CapriRacer

Sorry, but the steel belts are neither radial nor circumferential. They are at about a 15° angle. And while the belt slows the “arching” affect down, it does not prevent it from happening.

I suppose this diagram is just wrong then?

[CapriRacer]

Originally Posted by orange4boy

I suppose this diagram is just wrong then?

Orange4boy,

I hope you understand that I am not singling you out for ridicule, but you've just demonstrated a point well worth repeating - and that is being careful to really understanding what it is you are looking at:

Notice the "steel belts" - they are sort of white. What direction do the cords in the belt appear to go? The cords look like black lines.

Originally Posted by orange4boy

The article is obviously an informed opinion and presented as such.....

Sgt. Storton's article may have been presented as such, but my interpretation is that the answer came first and Sgt. Storton added "facts" to support his position.

One such "fact" was, as I pointed out, that the civilian and the police pursuit versions of the Crown Victoria have different inflation pressures - contrary to what Sgt. Storton wrote. That is not the only error in the article, but it is telling that all he needed to do to confirm it (or deny it) was to go down to the Ford dealer - and he obviously didn't.

But these errors go to the fundamentals. Once you remove them, his arguments have no technically sound basis. It's just a guy spouting his opinion - which is fine so long as everyone understands that.

Unfortunately, many folks will read this article and form an opinion, not realizing how truly unsupported his claims are.

And that, my friends, is one of the problems with the internet. You can find a web page to support almost any position you take:

Flat earth? Yup.

Melting ice cap. Ice cap is not melting. Yup, got both of those!

It is important that we recognize what information is real and what is not. And more importantly, no information means no information. It doesn't mean lack of contradiction.

[natefish]

Originally Posted by CapriRacer

Here’s the problem I have with Sgt. Storton’s article:

1) “…..The reason the owner’s manual lists 35 psi is because we get the same manual as the civilian version of the Crown Victoria. The police version, however, is fully loaded with communications equipment, a cage, and your gear. You are not looking for a soft and cushy ride, you want performance…..”

Sorry, but the civilian version does indeed have a different inflation pressure than the police version – and the police version has more . Obviously, the folks at Ford did compensate for the additional weight that is going to be carried by a cruiser.

Perhaps the article was accurate in 2005 when it was published. Mr. Storton seems to have a pretty good list of qualifications after his name, I doubt he just made stuff up for fun.

Can you provide the source the makes you think he is wrong?

Originally Posted by CapriRacer

2) “…..The proper tire pressure for the Police Crown Victoria is 44 psi. If you look on the sidewall of the tire, you will see that it lists 44 psi max pressure….”

Yes, it lists the MAXIMUM pressure as 44 psi, but it does not list a RECOMMENDED pressure. Sgt Storton doesn’t explain HOW he arrived at the 44 psi value.

But later versions of the tire supplied to the Police Pursuit versions of the Crown Victoria have tires where the sidewall lists 51 psi as the maximum, so what about that?

I read this as his way of saying, for extreme driving, you should ignore the door placard and go with the maximum sidewall pressure. So in the case of a tire with a max sidewall pressure of 51 psi, the correct tire pressure would be...51 psi. I could be wrong in my interpretation though...

Originally Posted by CapriRacer

3) “… The tires will not balloon out creating a peak in the center portion of the tread when tire pressure is above 35 psi. There is a steel belt that prevents this from happening….”

Sorry, but the steel belts are neither radial nor circumferential. They are at about a 15° angle. And while the belt slows the “arching” affect down, it does not prevent it from happening.

I agree, but wouldn't you mostly run into this outside of the tire's specs (ie over recommended max psi)? Just in thinking about it that seems to make sense to me, but leaving me to my own thoughts can be dangerous

Originally Posted by CapriRacer

I am not even going to go into the issue of the “Stunts” involving Ranger pickups.

I think the reason this article has been pulled is that it is full of misconceptions and does not back up the things that are put forth as “facts”.

I think perhaps the article was pulled because it was old and/or practices changed. Based on the "last updated" date, it looks like it wasn't removed until two and a half years after it was published. All in all, I thought it was a decent article that provided some good insights and information from someone with extensive first hand experience in their industry.

[orange4boy]

First you wrote this:

Originally Posted by CapriRacer

Sorry, but the steel belts are neither radial nor circumferential. They are at about a 15° angle. And while the belt slows the “arching” affect down, it does not prevent it from happening.

Then I posted the diagram. Then you posted this:

Originally Posted by CapriRacer

I hope you understand that I am not singling you out for ridicule, but you've just demonstrated a point well worth repeating - and that is being careful to really understanding what it is you are looking at:

Notice the "steel belts" - they are sort of white. What direction do the cords in the belt appear to go? The cords look like black lines.

Oh, I know what I'm looking at. Those are woven steel wire belts that run around the circumference of the tire. The individual wires are angled, yes, but as a whole they run around the circumference of the tire.

And that, my friends, is one of the problems with the internet. You can find a web page to support almost any position you take:

I agree there is a difference between some guy's opinion and solid, good information. That's why I found scientific and government studies as well as textbook references that support my positions.

You have yet to do so. For now I will have to treat your opinion the same as I do "some guy" although since I have found information that supports Sgt. Stockton's opinion, I am inclined to mostly believe his opinions on driving at max sidewall.

[autoteach]

Well, I have to weigh in, although it seems that my opinion, like others, will be dismissed because "we don't know". Belts in automotive tires, unless specified, are at ~15 degrees. Try to even wrap a piece of tape around your tire repeatedly at this angle. How many revolutions did you get around the circumference? Some tires are 0 degree belted, but are mostly found in motorcycle tires where deformation at lean angle becomes important. Because of this...
Tires do bulge at the center, pressure does affect traction, and stopping distance, and not in the way that you are describing. I have, and I suppose that it will be argued, more experience than most(albeit the few who have worked in racing/automotive repair) with tire inflation. I have seen car, truck, and heavy duty truck tires that have experienced life at various tire inflations. All of the over inflated tires have worn faster in the middle, all the under inflated had worn on the outsides. This starts to happen in less than 5000 miles to a measurable(meaning able to be determined with measurement) degree. Both over inflated and under inflated tires drastically affect handling of the vehicles, in accel, brake, and lateral, and for the vehicles that travel down the road, there isn't a good blanket policy that you can apply to them.

I won't come back to argue, as I know my data. My toyota pickup (1989) called for 35psi, this would make the rear of the vehicle harsh, and unpredictable. Minor amounts of throttle could break them loose, wet or dry. 4wd would not engage in any favorable way. The center began to wear considerably within one oil change. Braking with these pressures would cause the rear tires to lock almost instantly. After this, I adjusted the tire pressure to accommodate sidewall height, which is relative to rolling diameter (not actual diameter). It improved all these aspects, which in my mind is far better than mpg. This has held true for almost every truck and car that I have seen in the last 15 years, and I doubt that it will change until tire construction changes.

[Christ]

No one is doubting your "knowledge". Don't take it that way. Just provide data to back up what you're saying. Data = something we can see, read, form an educated opinion based on... etc.

Not your unprovable experience.

Sorry if this makes you feel like nobody's listening to your opinion, but we don't take opinion worth much when Data is what we're looking for.

Provide something material that we can see, and your thoughts will be noted.