Technical Tire deterioration / When should you buy new ?

I am in the process of a cross country move and was going to drive my car cross country. (3500 km) The Coker WW that were on it were installed 9 years ago and who knows how old they were before installing them. (I couldn't find a date code) What really stung was there was only 8000 miles on those tires and all 4 had sidewall cracks. And the cost these days in Canadian dollars for 4 new ones is crazy. So, just before the trip I found a shop that sells wide whites and bit the bullet on 4 new DiamondBacks. Better to be safe than sorry.

 

My internet access is through my slow phone.

What's the supposed misconception?

 

The actual misconception is in post #10 and post #25. Two identical vehicles traveling 25 MPH and colliding head on is not the same as one vehicle hitting an immovable brick wall at 50 MPH. The article below references the Mythbusters test proving your "additive force" scenario is incorrect.

Head-on collision math
Consider two scenarios:

1. Two identical vehicles (same size and mass) travel at the same speed, let's say 50 km/h, in opposite directions, and they collide with each other head-on.
2. One of those vehicles hits a rock wall (which doesn't break nor budge in any significant way) head-on at 50 km/h.

From the point of view of one of the vehicles, which collision is more severe?

Most people would instantly answer that the first collision is more severe because the effective collision speed is 100 km/h, and thus the collision has twice as much force than the second collision, which happens only at 50 km/h.

This answer is wrong, wrong, and utterly wrong. Many people just don't get this one, not even people who should know better. I can't even count how many times I have heard people getting this one wrong.

The most prominent and severe case which I have seen was Jamie Hyneman from the show MythBusters getting this exact problem wrong in their "demolition derby special" episode, where he stated that two trucks travelling at 50 mph each and colliding head-on were subject to a collision force equivalent to hitting a rock wall at 100 mph. Maybe he is not a phycisist, but nevertheless he of all people should know this.

The correct answer is: The two collisions are completely equivalent. From the point of view of one of the vehicles it makes absolutely no difference whether it hits a rock wall at 50 km/h or another identical vehicle which was traveling at the same speed in the opposite direction. The amount of force applied to the vehicle is the same in both situations.

(Ok, in reality there will be some differences because the consistency of a rock wall is very different from a consistency of a vehicle, but this only means that hitting the rock wall will be more severe than hitting the other car, although probably not by a lot.)

I know that no matter how much this is explained, some people just don't get it. They just can't get rid the misconception that the two-vehicle collision must have double the force. There are a few things which might make it easier to accept:

When the vehicle hits the rock wall at 50 km/h, the rock wall causes a force large enough to stop the vehicle right there. In other words, the vehicle hits the rock wall with a momentum equivalent to its speed times its mass. Conversely, by Newton's law, at the moment of the collision the rock wall causes an equal force to the vehicle in the opposite direction, causing it to stop. That is, the rock wall causes a force equivalent to the 50 km/h times the mass of the vehicle.

The misconception in the two-vehicle scenario is basically that this applied force is double that, ie. the equivalent to 100 km/h times the mass of the vehicle.

However, think about where this force is coming from in the two-vehicle scenario: It's coming from the second vehicle. But the second vehicle is also traveling at 50 km/h and has the same mass.

So we have two forces: Vehicle 1 applies the equivalent of 50 km/h times its mass to vehicle 2, and vehicle 2 applies an equal force to vehicle 1. This causes both vehicles to stop right there.

Where would the additional 50 km/h times the mass of the vehicle come from? Vehicle 1 cannot apply that force to itself. It's applying it to vehicle 2. So where is it coming from?

The answer is that it's not coming from anywhere because the force applied to vehicle 1 is not 100 km/h times the mass, but only 50 km/h times the mass. The same as with the rock wall.

Think also about this: If you applied a force equivalent to 100 km/h times the mass in the opposite direction of vehicle 1, that would actually make vehicle 1 change direction and go backwards at 50 km/h after the collision. Conversely it would also make vehicle 2 do the same. That doesn't happen.

Think about it like this: If vehicle 1 couldn't "see" what it hits, how can it tell if it hit a rock wall or vehicle 2? The "point of impact" remains stationary in the two-vehicle case, in the exact same way as in the one-vehicle-and-rock-wall case. From the point of view of vehicle 1, there's no difference.

 

I haven't read your entire reply, yet. But, the math is provided through physics, which I'll have to look up. But it boils down to momentum and conservation of energy. Masses (not weights) and velocities:
m1*v1 = m2*v2

Then you solve for each post-collision velocity:
v1 = (m2/m1)*v2 ;
v2 = (m1/m2)*v1

That's how the total impact energy is shared.

A good reality check comes from making the variables more extreme so it's easier to understand.

A 3,000-pound car going 25 mph collides head-on with an 80,000-pound semi-truck going 75 mph. The energy is added, and the lighter, slower vehicle takes the brunt of the impact.

The wall scenario is similar, but the wall has no initial velocity.

 

The problem with the article is that it tries to compare two cars moving in opposite directions with one car and a fixed wall. The article doesn't do the math, either. The article (mistakenly) doesn't distinguish (confuses, conflates) force and energy. By making their masses and speeds equal, it helps hide this mistake. Each car has momentum, which is energy. Both cars' energy is transformed in the collision. The energy each car receives is determined by the speed and mass of the opposing car relative to its speed and mass.

The question the article needs to resolve is: Where did the energy from the second car go?

The wall has no initial energy because it's not moving initially. If the wall was moving in the opposite direction (like the car), the energy would be added, also.

The force each object experiences is determined by Newton's Second Law of Motion, F = m*a, where a is the deceleration, which is the change in velocity (forward to stopped or reversed direction) over time (which is milliseconds in a collision).

 

Growing up on a farm and working for various neighbors I can say that most farmers are living on borrowed time. Single axle and tandem axle trucks were the norm years ago. Tires got replaced as needed. Being overloaded, driven on gravel, sitting in the sun, being over a decade old, and somehow the tires rolled on.

 

My mom had the spare for her 3/4 ton pickup blow while it was laying in the bed of her truck sitting in the yard in front of her house. That does happen.

Think about how many car/boat trailer tires you see blow/blown on any road trip you go on. Rigs that sit far more than they go and the tires may be a number of years old. The three tires that are left on my sailboat trailer still look like you could run them 25 thousand miles but they are 17 years old and the 4th one blew on the way home from a boat trip three years ago. I'd have to look at the title to see how old my trailer for the Bayliner is but I'd bet that the tires on it came from the factory on it. That boat was only used for Salmon fishing by the previous owner and only moved from it's spot in the yard during fishing season.

 

Tires were made of better materials in the past. On this Dragster, back in '86, all 4 tires were a minimum of 16 years old. I ran over 192 and didn't even give it a thought.

 

That's a bold and broad statement, which may have some truth to it. But I think tire technology has improved, overall.

 

I haven't and won't read the debate concerning whether a single car hitting a wall @ 50mph is or isn't the same as 2 cars, ea. @ 25mph hitting head on. Why??? Because the topic here is tires and when they become hazardous to continue to drive on them, using age as the determining factor.
I'm 83 and been driving about 70 of those years, a helluva lot of them on bias ply tires, and now all radials. Jim Forbes and I have just about the same theory on the why of age being so much more of a determining factor on replacing your tires with radials vs bias.
With bias ply, I have to admit, I sometimes drove them "until you could see the air inside". Have had many blowouts, and always maintained control when they happened. Never wrecked a vehicle from a blowout.
A few years ago I experienced my first and only blowout on a radial tire, on the left rear on a pickup truck. Was really a case of a broken belt which then separated and while it did lose all the air and go down, I was able to hold my lane (on Xway) and pull over to shoulder.,
But that broken belt never completely left the tire carcass and with it having steel belts, if beat the living Hell outta that quarter panel and wheel housing Fortunately the truck was a bit of a "beater", and the damage didn't matter all that much
But I haven't forgotten that incident, and sure wouldn't want that damage to the fenders on my '40 Ford coupe, plus if it happened the same way on my fenderless hiboy roadster, that flapping belt could get all sorts of tangled up in the exposed steering components A blowout on a radial just isn't the same as one with bias ply.
I don't try to run the tires any longer "local" than highway, as to me "local" could be just downtown @ 35-45mph or it could mean 5-10 miles on an X-way @ 65-75, or maybe a bit more if I'm feeling frisky!
It hurts to pull them off, still looking so good, but I think 9-10 years is enough.
But the thing I wonder about is how Inna Hell do all these used tire dealers avoid liability for what they are selling?

 

Most bias ply tires don't have steel belts, so they don't have the tread separation problem of radials.

Sent from my Trimline

 

This brings up a point that's seldom mentioned... how the tires are stored, whether they're on the car or not. Leaving a tire in contact with soil over extended periods without moving allows the organics in the soil to attack the rubber, breaking it down. Anybody who has retrieved a car that spent years sitting in a field has seen an extreme case of this; the part of the tire that was in the dirt is rotten, and a damp climate will accelerate this. Even concrete can cause issues if moisture is present as that can cause leaching of organics out of the cement. The 'old time' practice of putting a car up on blocks during extended storage (back when many garages still had dirt floors) shows to me that this used to be a known issue that somehow became ignored. So a car/truck/trailer that sits for weeks or months at a time is slowly damaging the tire rubber. These rarely accumulate many miles so the tires don't 'wear' but when you do take it out and the tire fails it's blamed on 'old tires' when the cause is probably improper storage.

 

this has been covered before - had a low mileage name brand tire collapse inside with no visual evidence of a problem - driving along at freeway speed and heard a thumping sound - pulled over and looked under truck, at tires, etc - took off and same results - pulled onto off ramp and called for a flatbed tow service - had a difficult time winching onto bed because one front tire had collapsed - looked like one of those single tire display stands - one of best (worst) scenes in movie "World's Fastest Indian" where Burt Munro put shoe polish on his tires sidewalls to fill cracks to make them look good - as mentioned above, trailer tires (and wheel bearings) of all types are usually neglected as to maintenance & safety checks

 

+1 on heat being a main culprit. I was living In Lake Havasu City AZ and working In Kingman AZ. I had 2 year old tires on OT car, when on my way to work one morning, drivers side rear tire exploded at about 75 mph., very nearly rolled over. After that, tires were replaced every year just before summer, regardless of condition.


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Bias ply tires will hang together for years .
Radial tires will not !
Radials are good for anywhere from 4 to 7 years , after that you are gambling
on whether they will stay together or rip your fender off .

 

It is large in part that older tires had real rubber and today's tires are all synthetic rubber. I can believe Marty's statement and bias ply tires.@squirrel was right on as usual with the bonding of the rubber to the steel belt. Running on an under inflated tire is hard on it but so is setting in one place for extended periods of time on a radial. My tire guy, that has never steered me wrong, (maybe pun intended) and I were talking about the seemingly premature tire failures on my equipment trailer. He suggested going to a bias ply tire as he explained that a radial tire that sits, sets the rubber at the point of contact with the surface it is setting on. When it rolls, the rubber breaks away from the steel on a small level and that is the start of a ultimate separation of the tread from the belting. My experience has been that a bias ply tire is better at surviving setting.

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I bought a set of radial TAs in the 90s, 255 70 I bought four, but only put two on the back of my truck The unused tires were wrapped in paper then sealed in plastic bags in a cool dark place. In 2005 I was making a long trip to I mounted and balanced the unused tires. 50 miles down the road the left rear blew. I installed a spare, and got back on the road. Less than a mile later the right rear blew. Fortunately I had two spares, so I was able to have two new tires installed on the rear of the truck, and drove 5,000 miles on the rest of the trip

 

"Every time a bell rings Daddy, you need to buy a new set of tires."

 

... This is why I always run biased plies on my hotrod ...

 

I change radials at seven years. I've seen what southern summer heat can do to an older radial tire more than once. Lucky it was never my car. It's amazing the damage a blown tire can. Beat the crap out of the left rear on a buddy's '47 Chevy convertible.

 

there are places that sell used tires - so, the ones that you have removed because of age end up at these shops and reused again - guy that can not afford new tires is not going to be looking for and figuring out date codes - have bought used tires to use as rollers while working on a project - had a project that had a couple of low mileage brand name tires on it - I liked the look but, not available anywhere to get two more - found a shop that found two "new" tires with stickers, etc - according to date code they were 5 years older than ones I had - guess discontinued style that ended up in a warehouse some place - buyer beware -

 

I guess that pretty much proves that as long as you store them in a reasonable environment they are OK, even if the date code says a decade or more has passed, eh?

 

I’ve read that as a tire flexes, it releases the oils in the rubber and keeps it flexible. Ever notice how dry a tire is on something that has been sitting a long time? I’ve heard it called dry rot, but actually it’s the oils in the rubber that don’t get released and the rubber stiffens up. It doesn’t seem to be as large a problem with bias plys, I have some trailer tires that are probably 30-40 years old that are cracked up and hard as a rock, but they hold air fine. In contrast, I have 10 year old radials on my Lincoln that are cracked and they leak through the sidewalls. They will be replaced before the car goes back on the road.

 

I recall hearing something about tires off-gassing, which means it's losing something to the environment.

And tires being exposed to the oxygen in the air is also affecting them.

https://www.westmarine.com/WestAdvisor/Trailer-Tire-Basics

 

That tells me I want to think very hard before I buy any more BFG tires...

I've owned three sets of BFG radial tires over the years, the last set was probably 20 years ago. I had trouble with every set (and they weren't 'aged') and finally quit buying them. I know these days finding the sizes we want isn't as easy as it once was, but there are other choices.

 

A slightly different slant.
A while back I bought some wheels from a guy.
They were in his garage, looked good, we made the deal.
He then said, "out behind the garage I have some other wheels.
You can have them if you dig them out." I thought I was going
to find a shed or out building with the wheels and tires in it.
Nothing but a mound of dirt.
I started kicking the dirt and sure enough, a wheel and tire appeared!
I dug a little more and found the other 3. A complete set.
He said take them for nothing. He said they had been there
since his father left them many years before.
I brought them home, hosed them off, and aired them up.
Put them on my car and cautiously drove to Friday nite cruise!
You know the drill, No pictures it didn't happen!
Here you are.
The car now belongs to Kevin, from South Jersey.

 

I guess you need to understand the differences between a radial and a bias ply tire to understand the "time frames".

The basic cords on a radial tire run from one tire bead, straight across the tire to the other tire bead. What this does is allows the sidewall to flex more because all the cords run across the tire, in a straight line from one side to the other. Generally there are two sets of cords, one laid on top of the other, both running straight across the tire, side to side. Then the tire manufacturers add belts that are basically strips of different material that lay under the tread, and go around the tire. There may be anywhere from 2 belts to 4 or more belts. These belts are bonded to the across the tire cords. They give the tread stiffness. The tread stiffness coupled with the sidewall flex of the radial cords give the tread a more uniform surface on the road, which is what causes the longer tread life, better traction, and improved fuel mileage.

The cords on a bias ply tire run across the tire from side to side, but they are at an angle. There are always multiples of 2 cords, one cord lays at one angle and the other cord lays at the opposite angle forming a cross pattern. the cross pattern gives the tire a stiffer sidewall, and allows the tread to deform more from the weight of the vehicle. There may, or may not be belts added like the radial tires have under the tread, most cheap bias ply tires don't have the belts, but the more expensive bias ply tires probably do. The belts on the bias ply tires do the same function as the belts on radials, but radials almost always have at least 2 belts.

The cross pattern of the cords in a bias ply tire actually create more heat in the tires as they are used, but because most of that heat is created in the tread, it has more effect on the tire tread then on the tire sidewalls, and since few bias ply tires have belts, when a bias ply tire is destroyed by heat, the tread separates from the cords and usually chunks of the tread come off and fly away. If the bias ply tire is belted, they can exhibit the same effect as a radial tire failure because the tread has to separate from the belt, or the belt has to separate from the cords.

Because most of the heat in radial tires is in the flexing sidewalls, there are more issues with the belts loosing the bond to the cords causing the belts to move then any other issue. Since the tread is bonded to the belts, when the belts move, the tread moves also, this compounds the issue. It is more difficult for the tread to separate from the belts, so the belts with the tread still attached become weapons until the belt can fully separate from the radial cords.

I suspect the time frames given on radial tire replacement is about equal to normal tire wear, most people put a lot of miles on modern vehicles in a year. Usually, the tire should be replaced, time wise, about the same time they should be replace tread wise. Its not the tire manufacturers fault you only drive your hot rod a thousand miles a year.

Bias ply tires often wear out before the age becomes an issue, and most of the time, a heat related issue with a bias ply results in a simple tire replacement because a chunk of the tread came off. Gene

 

I recently read about a space-saver spare exploding and doing considerable damage to the trunk. My car is not going anywhere for some time, so I deflated the spare.

I inherited my dad's Tbird. He had tubeless radials mounted on Kelsey Hays spoke wheels. Having read negative things about using tubes with tubeless tires, and knowing that only the 1962 Tbird offered spoke wheels as a factory option, I sold the wheels and tires to an elderly gentleman, who intended to put them on his 30s Dodge. I bought new wheels and tires, just before beginning the car's restoration. Not wanting the tires to develop flat spots, I removed them, had throw-aways mounted on original wheels, and put new wheels and tires in inside storage. I will probably have to replace the "new" tires before putting the car back on the road, just to be safe. Apparently they can rot from inside because oxygen retains moisture-might be a good reason to inflate tires with nitrogen. After reading these posts, maybe I should deflate the "new" tires, too. 2 are stored in my basement, near the water heater, and 2 are stored in the loft of my garage.

By the way, Kelsey Hays wheels look great, but most of the 55-57 Tbirds I see have them.

 

No offense intended to Joe H, but this really doesn't help the situation. If the old tires were then fittd to a road-using vehicle, the possible danger still exists. What would be a real mind-f##k is if the tires failed and caused the buyer to slam into you or some-one you loved.

This is a much more sensible approach. If they are too old for your car, they are too old for any car.

 

Might find this report of interest, Report to Congress on Tire Aging, this was the result of the Ford Explorer incidents.

https://dig.abclocal.go.com/kgo/PDF/Tire_Aging_NHTSA.pdf .

Personal experience: 5 yr old TAs on 64 Malibu replaced due to cracking in tread area, not real bad but bad enough. 2 yr old Michelin, factory install on truck replaced due to tread cracking that you could inset a dime over 1/8", Tire dealer techs inspected and rated as cosmetic, no fault of the manufacturer.

Michelin/BFG won't be a part of any of our short lists in the future for tires.

With the report to congress hi-lighting the effects of heat and sunlight, my tires should outlast the vehicles, live in the garage when not driving and our temps here are a long way from those experienced in Arizona.

Live safe friends