Interesting tire failures...

[CapriRacer]

Originally Posted By: used_0il
The most obvious tire failures are the tread separations from large trucks using re-capped tires......



I just want to be clear, that it isn't the recap that is failing. It's the casing that is failing - and mostly this is due to the number of times a tire gets recapped. It's a durability failure.


Originally Posted By: used_0il
....You can see these "alligators" along side of the highway, or you might drive over one.

Under inflation or running flat would be the most likely cause of this type of tire failure........


Run Flat failures are distinctively different than casing failures. Run Flats are basically sidewall failures - in that when a tire is deflated, the tread is trying to rotate at one speed, but the wheel is running at another speed, and that difference results in rubbing in the inside and the outside of the tire. It sort of tears the sidewall apart.


Originally Posted By: used_0il
...... Tire re-cap plants say those tread separations are not a result of failure of the bonding agent, but "case failure".

OK, what is case failure?.......


I think they mean casing failure - and that is a fatigue failure - that is, the number of rotations (cycles) the tire has been subjected to, vs the load on the tire.

Look up "Fatigue (Material)" in Wikipedia.

Wikipedia - Fatigue (material)
Pay particular attention to the SN Curve. It is the key to understanding how things can fail from extended usage.


Originally Posted By: used_0il
......
Does the separation of tread from tire occur as "belt leaving belt" or sidewall problems?....


The typical tread separation is a belt leaving belt separation. It is caused by a fatigue failure under the edge of top belt - which is the most highly stressed area in a tire.

There are lots of things that can be done in the design to improve the fatigue life in this area, but the most visible to the average consumer is the use of cap plies - the more the better.

Originally Posted By: used_0il
...... (I think I just gave away what I've been reading today.)....


Yes, you did!!

 

[userfriendly]

I understand that cap plies prevent a tire from growing due to
centrifugal force at high speeds.
Therefore a high speed rated tire (Y) would likely have more and stronger
cap plies than a lower speed T tire would have.

A quick trip outside to look at the construction information on the sidewalls
of my pick-up states;
tread 2 plies polyester 3 plies steel, sidewall 2 plies polyester, 126R

The spare of the same brand and type, but 265/70/18 instead of 275/65/20 states;
tread 2 plies polyester 2 plies steel 2 plies nylon, sidewall 2 plies polyester 124S

Both are Michelin AT2s, not a great winter tire, but they have a mileage and road hazard
warranty from Costco.

Another look at some steel cased 19.5s at work indicate a 1 steel sidewall 3 steel belt
construction.

Nitto has a "Dura-Belt", 3 steel on a few of their Grappler sizes that are likely 2+3
construction.

Since cap plies add the the integrity of a tire at speed, nylon is cheap and light weight
and the price of these tires high, why on earth after all the legal problems Firestone
had (twice) would a tire company send the public a tire with no cap plies?

A tire failure is not only a danger to the vehicle on which it occurs, it is also poses a danger to other motorists.

Where I work it is called redundant layers of safety, so if one component fails,
the system does not fail.

 

[CapriRacer]

Originally Posted By: used_0il
I understand that cap plies prevent a tire from growing due to
centrifugal force at high speeds.
Therefore a high speed rated tire (Y) would likely have more and stronger
cap plies than a lower speed T tire would have.

A quick trip outside to look at the construction information on the sidewalls
of my pick-up states;
tread 2 plies polyester 3 plies steel, sidewall 2 plies polyester, 126R ......


3 plies steel? But no cap ply? Interesting!

Originally Posted By: used_0il
..... The spare of the same brand and type, but 265/70/18 instead of 275/65/20 states;
tread 2 plies polyester 2 plies steel 2 plies nylon, sidewall 2 plies polyester 124S

Both are Michelin AT2s, not a great winter tire, but they have a mileage and road hazard warranty from Costco.......


OK, it is important that we include the letters in front of (or behind) the numbers in the tire size, because they change things.

In this case, the 265/70R18 is a P type tire and the 265/65R20 is an LT type tire - speed ratings T and R respectively.

That makes a significant difference in how those tires SHOULD be constructed.

Originally Posted By: used_0il
....... Another look at some steel cased 19.5s at work indicate a 1 steel sidewall 3 steel belt construction.

Nitto has a "Dura-Belt", 3 steel on a few of their Grappler sizes that are likely 2+3 construction.

Since cap plies add to the integrity of a tire at speed, nylon is cheap and light weight and the price of these tires high, why on earth after all the legal problems Firestone had (twice) would a tire company send the public a tire with no cap plies?......


That is an interesting question, but I think it assumes that cap plies are the only way to improve the integrity of a tire - and that is not the case.

It also assumes that the different types of tires react the same way - and that is not the case, either.

Originally Posted By: used_0il
....... A tire failure is not only a danger to the vehicle on which it occurs, it is also poses a danger to other motorists.

Where I work it is called redundant layers of safety, so if one component fails,
the system does not fail.


Unfortunately, the components in a tire don't act independently. Plus there are a lot of ways to improve the durability of a tire - and some of them don't involve cap plies.

I wonder if the 3rd steel belt ACTS like a cap ply - and without tearing the tire apart, we just won't know.

Needless to say, this is a complex arena and it helps to sort the ducks from the geese.

 

[userfriendly]

Or the green rubber from the green ham and eggs.

I've come to some conclusions upon reading through your material that one of the
performance criteria of OEM tires is rolling resistance.

This would be an important area of concern as auto manufactures must meet
fleet fuel economy targets.

You mentioned in your text that a worn tire will have a lower rolling resistance
than the same tire when new.

Also if I read the following correct, is that a reduction in aspect ratio along with
the necessary increase in rim diameter to keep the tire diameter the same, also results
in a reduction of rolling resistance.

From the above, I came to the conclusion that auto manufactures will pick a tire and rim
combination that is low profile, half worn out when new and of a light weight construction.

No one in the tire industry would want to change that fact of mine, because it would
hurt the bottom line.

The benefit curve that a tire contributes to the fuel economy of the country, in your case
USA, has to be plotted against all the related down stream costs that each tire goes
through from raw material acquisition, manufacture, shipping, installation, replacement,
disposal and legacy (pensions).

If longer lasting tires were installed on new vehicles in the first place, all those
extra workers could be doing something else instead.

 

[CapriRacer]

Originally Posted By: used_0il
Or the green rubber from the green ham and eggs.

I've come to some conclusions upon reading through your material that one of the
performance criteria of OEM tires is rolling resistance. This would be an important area of concern as auto manufactures must meet fleet fuel economy targets.......


And I would add that it is a MAJOR consideration - much more so than wear or traction.

Originally Posted By: used_0il
..... You mentioned in your text that a worn tire will have a lower rolling resistance than the same tire when new.

Also if I read the following correct, is that a reduction in aspect ratio along with
the necessary increase in rim diameter to keep the tire diameter the same, also results in a reduction of rolling resistance.......


Actually, I think it is the opposite.

What car manufacturers do is use the same load carrying capacity, not the tire diameter (both of which are pretty closely related.) - and if you do that, an increase in wheel diameter results in a lower aspect ratio AND a wider width.

That increase in width results in worse RR - BUT - the effect is really small. We're talking single digit percentages. Not enough to worry about.

Originally Posted By: used_0il
...... From the above, I came to the conclusion that auto manufactures will pick a tire and rim combination that is low profile, half worn out when new and of a light weight construction........


Actually what they do is change the tread rubber compound - which has a HUGE effect on RR. But that also has an effect on wear rate and traction - hence the reason why OE tires are generally looked on as "cheap". They aren't less expensive - they just wear quicker (and/or take more distance to stop).

Originally Posted By: used_0il
....... No one in the tire industry would want to change that fact of mine, because it would hurt the bottom line.....


Actually, the car manufacturers set the specs and the tire manufacturers have to comply. The tire manufacturers would rather the car manufacturers NOT specify RR as good RR is not a thing that the average consumer values, but good wear and good traction are.

Originally Posted By: used_0il
.....The benefit curve that a tire contributes to the fuel economy of the country, in your case USA, has to be plotted against all the related down stream costs that each tire goes through from raw material acquisition, manufacture, shipping, installation, replacement, disposal and legacy (pensions).

If longer lasting tires were installed on new vehicles in the first place, all those
extra workers could be doing something else instead.


There are a lot of myths surrounding a tire's RR, but the one that is most counter-productive is that you can get better fuel economy without any sacrifice. Sorry, but the Physics say otherwise.

Whether a tire with a better RR results in an overall better situation, or not, I think depends on how you look at it. If you only consider fuel, then I think the lower amount of fuel consumed by a low RR tire offsets the amount of fuel needed to produce replacement tires.

HOWEVER, if you consider that more tires would need to be disposed of, you probably come up with a different answer.

Some time back, the California Energy Commission was tasked by the state legislature to try improve the fuel economy due to tires - and they failed. They could not come up with a viable way of regulating the RR of tires, nor could they overcome the disposal problem.