Tyre construction and an observation.

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Tyre construction and an observation.

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Tyres is a subject which often comes up on the forum. Many will have some idea as to how they are manufactured but I thought this video might be of interest:



Now a days, as you can see in the video, standard road tyres are produced with a minimum of human intervention but back in the Late 60s, when I worked out of the Firestone factory in Brentford, the tyres were all layed up by hand. It was a very dangerous place to work with heavy rolling mills for mixing the rubber and sharp knives for cutting the stock to length as it was applied to the building drum. That's before you started dodging the spiders and snakes which occasionally came in with the bales of natural rubber!

Now to the reason for me posting all this "drivel". If you've watched the video above you'll now understand that the tyre is built up in layers. The last of these layers to be added is the tread rubber. If you look at this picture I took recently of one of the tyres from the Mazda you can clearly see where the tread rubber and sidewall rubber join. Look at the edge of the tread pattern at around 1.00 o'clock to 2.30 o'clock in this picture:

P1100967.JPG


Because of the way the light is falling on this image, you should be able to see quite clearly the delineating line between the tread rubber which is a completely different compound to the sidewall rubber. You can see this on most tyres and once you know this it gives you something else to look for when out shopping with the wife and bored out of your mind! Ha, Ha! But seriously, there is a point to this which is: Tread rubber is very tough and clever stuff, having to be able to provide grip in differing road conditions whilst at the same time providing resistance to wear so the tyre will last. The sidewall uses a very different compound as it has to be both tough - to protect the casing construction and "super flexible" to withstand the 3D flexing as the weight of the vehicle deforms it with every revolution but it doesn't need much abrasion resistance. When the tyre cures in the mould the casing rubber and tread rubber bond chemically and physically together. In fact this is a big quality control area as any imperfection introduced during building between the case and tread might well result in them failing to bond with the serious consequence that the tread may well separate in service and throw bits of tread off. (in racing, back in the day, we called it "chunking"). Even touching this interface was taboo as the sweat on your finger could cause the raw rubber to fail to bond. - Raw rubber, before it's cured is very "sticky" the surface is not unlike when you put the glue on an innertube before you stick the patch on.

So here's the "thought for the day" The tread rubber band is roughly the same thickness as the depth of the tread pattern, wee bit more on some. When the curing takes place a "mingling" layer is produced at the interface between the tread and casing rubber - this is everywhere under the tread rubber - so, if you think about it in cross section, starting off with the casing rubber, you then have a thin layer of intermingled casing and tread rubber and finally on the outside, the tread rubber. Tread rubber is designed to resist wear and abrasion whilst casing rubber is not. What does this mean? Well, when your tyres get well worn they might get into the area where this "mingled" layer is. If that happens the wear rate will become very rapid and can easily catch you out. If you look out for your tyres and check them regularly there's little risk of you experiencing this because you'll be checking pressures and looking at the tread depth right across the full width of the tyre. In my experience it's not unusual to find tyres wearing more on the inner shoulder and this is easy to miss as the tyre often looks fine from the outside. - turn your steering wheel full lock when checking to see both outside and inside shoulders of the tread. If you notice wear like this on your tyres it may just be that it needs checked for suspension wear and get the toe reset but also often it's a pointer to the rubber bushings on the suspension arms getting soft and allowing the front wheels to splay out a bit under braking. As most people know, the legal limit in our country is 1.6mm. Keep a regular check on your tyres, as most manufacturers now mould wear indicators into the tread - illegal when the indicator is flush with the surface of the tread. Many have little TWI letters on their sidewalls to help you find them - but remember if it's flush it's actually illegal right now, so we used to recommend changing at 2mm and I see some manufacturers are now recommending you think about renewing a tyre when it's showing 3mm. I find that particularly interesting as I got involved in doing testing tyre wet weather performance and we found that a tyre with anything under 2mm, on a properly wet road, not talking standing puddles here though, might as well be bald for all the difference it made to braking distances.

I think there are a number of factors in play with older worn tyres. Probably the biggest one affecting wet weather is the tread depth because if the tyre can't displace the water it's going to ride up on it, like a surfer, and then you're aquaplaning so have no grip at all! A big factor which few think about is that rubber oxidizes, becomes hard with age and grips a lot less well - one of the biggest reasons why your car seems to "feel" and handle better on new tyres - It's worth considering though, that if you run your treads really low and end up running on the "mingled" layer of rubber then not only will the wear rate greatly increase but also grip will be substantially compromised.

So, next time you're wandering down the street, add tyre watching to your activities, there's a bewildering number of tread pattern designs and defects to amuse yourself looking out for. If I ever get a "smart 'phone" I think I'll start a picture library of what I see.

Edit: If you're still reading you might like this: https://www.bathwicktyres.co.uk/tyr...egal limit of 1.6,the inner, centre and outer.
 
Regarding the above, the definition given on that website was this: "The legal minimum tread depth for car tyres in the uk is 1.6 millimeters, across the central ¾ which is 75% of the tread around the complete circumference of the tyre." I believe that it should also state that even in any areas outside that central 75% of the tread width, the original pattern must still be visible? I've seen tyres on cars with suspension problems where the majority of the tread might be 4 or 5 mm but round, let's say (because it's common) the inside shoulder of the tyre is completely bald , may even be down to the cords! This would be illegal - and very dangerous of course.

Mind you, good luck with arguing with the boys in blue if their tread depth gauge shows less than 1.6mm anywhere, and actually, I'd be up there supporting them. Defective tyres are killers!
 
Tyres is a subject which often comes up on the forum. Many will have some idea as to how they are manufactured but I thought this video might be of interest:



Now a days, as you can see in the video, standard road tyres are produced with a minimum of human intervention but back in the Late 60s, when I worked out of the Firestone factory in Brentford, the tyres were all layed up by hand. It was a very dangerous place to work with heavy rolling mills for mixing the rubber and sharp knives for cutting the stock to length as it was applied to the building drum. That's before you started dodging the spiders and snakes which occasionally came in with the bales of natural rubber!

Now to the reason for me posting all this "drivel". If you've watched the video above you'll now understand that the tyre is built up in layers. The last of these layers to be added is the tread rubber. If you look at this picture I took recently of one of the tyres from the Mazda you can clearly see where the tread rubber and sidewall rubber join. Look at the edge of the tread pattern at around 1.00 o'clock to 2.30 o'clock in this picture:

View attachment 426825

Because of the way the light is falling on this image, you should be able to see quite clearly the delineating line between the tread rubber which is a completely different compound to the sidewall rubber. You can see this on most tyres and once you know this it gives you something else to look for when out shopping with the wife and bored out of your mind! Ha, Ha! But seriously, there is a point to this which is: Tread rubber is very tough and clever stuff, having to be able to provide grip in differing road conditions whilst at the same time providing resistance to wear so the tyre will last. The sidewall uses a very different compound as it has to be both tough - to protect the casing construction and "super flexible" to withstand the 3D flexing as the weight of the vehicle deforms it with every revolution but it doesn't need much abrasion resistance. When the tyre cures in the mould the casing rubber and tread rubber bond chemically and physically together. In fact this is a big quality control area as any imperfection introduced during building between the case and tread might well result in them failing to bond with the serious consequence that the tread may well separate in service and throw bits of tread off. (in racing, back in the day, we called it "chunking"). Even touching this interface was taboo as the sweat on your finger could cause the raw rubber to fail to bond. - Raw rubber, before it's cured is very "sticky" the surface is not unlike when you put the glue on an innertube before you stick the patch on.

So here's the "thought for the day" The tread rubber band is roughly the same thickness as the depth of the tread pattern, wee bit more on some. When the curing takes place a "mingling" layer is produced at the interface between the tread and casing rubber - this is everywhere under the tread rubber - so, if you think about it in cross section, starting off with the casing rubber, you then have a thin layer of intermingled casing and tread rubber and finally on the outside, the tread rubber. Tread rubber is designed to resist wear and abrasion whilst casing rubber is not. What does this mean? Well, when your tyres get well worn they might get into the area where this "mingled" layer is. If that happens the wear rate will become very rapid and can easily catch you out. If you look out for your tyres and check them regularly there's little risk of you experiencing this because you'll be checking pressures and looking at the tread depth right across the full width of the tyre. In my experience it's not unusual to find tyres wearing more on the inner shoulder and this is easy to miss as the tyre often looks fine from the outside. - turn your steering wheel full lock when checking to see both outside and inside shoulders of the tread. If you notice wear like this on your tyres it may just be that it needs checked for suspension wear and get the toe reset but also often it's a pointer to the rubber bushings on the suspension arms getting soft and allowing the front wheels to splay out a bit under braking. As most people know, the legal limit in our country is 1.6mm. Keep a regular check on your tyres, as most manufacturers now mould wear indicators into the tread - illegal when the indicator is flush with the surface of the tread. Many have little TWI letters on their sidewalls to help you find them - but remember if it's flush it's actually illegal right now, so we used to recommend changing at 2mm and I see some manufacturers are now recommending you think about renewing a tyre when it's showing 3mm. I find that particularly interesting as I got involved in doing testing tyre wet weather performance and we found that a tyre with anything under 2mm, on a properly wet road, not talking standing puddles here though, might as well be bald for all the difference it made to braking distances.

I think there are a number of factors in play with older worn tyres. Probably the biggest one affecting wet weather is the tread depth because if the tyre can't displace the water it's going to ride up on it, like a surfer, and then you're aquaplaning so have no grip at all! A big factor which few think about is that rubber oxidizes, becomes hard with age and grips a lot less well - one of the biggest reasons why your car seems to "feel" and handle better on new tyres - It's worth considering though, that if you run your treads really low and end up running on the "mingled" layer of rubber then not only will the wear rate greatly increase but also grip will be substantially compromised.

So, next time you're wandering down the street, add tyre watching to your activities, there's a bewildering number of tread pattern designs and defects to amuse yourself looking out for. If I ever get a "smart 'phone" I think I'll start a picture library of what I see.

Edit: If you're still reading you might like this: https://www.bathwicktyres.co.uk/tyre-tread#:~:text=The legal limit of 1.6,the inner, centre and outer.

Some years ago we were given a tour around the Bridgestone tyre factory and even my wife found it interesting even though she’s not really a car person. My biggest memory was the smell but I guess it was something you would get used to eventually.

As you say tyre age is very important especially to anyone who runs a low mileage classic or “Sunday” car. I’ve ditched tyres due to age, even though one pair had a reasonable amount of tread left but the difference in performance is very noticeable with the new rubber. After 8 to 10 years tyres are past their best and should be changed. Also it’s always worth checking the dates on new tyres, especially important if they are going on a performance car but even on a run of the mill car you don’t want tyres that have sat on a shelf for a couple of years.
 
So, next time you're wandering down the street, add tyre watching to your activities, there's a bewildering number of tread pattern designs and defects to amuse yourself looking out for.
This is a terrible habit.....which unfortunately I have.

Main one I remember is looking at Ford Ka and thinking "there's something wrong about that but can't place it".

Eventually realised it had Michelin MXs on it...a tyre that both went out of production before the Ford in question had started production and were falling out of use in the 90s.

The car was a 2007....I'd only remembered the tread pattern because my Uno had one as an original equipment spare from 1991.

Oh and it was about 2019....
 
This is a terrible habit.....which unfortunately I have.

Main one I remember is looking at Ford Ka and thinking "there's something wrong about that but can't place it".

Eventually realised it had Michelin MXs on it...a tyre that both went out of production before the Ford in question had started production and were falling out of use in the 90s.

The car was a 2007....I'd only remembered the tread pattern because my Uno had one as an original equipment spare from 1991.

Oh and it was about 2019....
At least it wasn't an X. I believe you can still buy that tread pattern for the 2CV/Dyane by the way.
 
You can still get the MX...just just in 155/60 13..given it was replaced by the MXL...then the MXT....and then probably about 7 other tyres between then and when I saw someone running one. It was fitted to an old Ford Orion steely which probably dates it somewhat.

Wouldn't rate it as a pass time...it's can be quite scary given I could tell you there's a Clio in my street that has 3 cords showing on the drivers side inner shoulder and an Astra that appears to have no rear brake pads.

That and it leads to appraising every car you say like you're about to buy it...saw an iX3 this morning, 2 years old in white. I'd imagine most people after 10 seconds of being in the presence of its first thought wouldn't be..."the owner is tight and can't drive..." None matching numberplates on 2 year old car...and the front one was just 5 letters and post code at the bottom...only places that don't like to advertise on the bottom of numberplates...body shops but legally you must have an identifier and postcode on any plate you make, I'd imagine the last 2 letters being RC stand for repair centre. Perhaps if it didn't have 4 budget tyres...he'd not have crashed who knows?
 
Some years ago we were given a tour around the Bridgestone tyre factory and even my wife found it interesting even though she’s not really a car person. My biggest memory was the smell but I guess it was something you would get used to eventually.

As you say tyre age is very important especially to anyone who runs a low mileage classic or “Sunday” car. I’ve ditched tyres due to age, even though one pair had a reasonable amount of tread left but the difference in performance is very noticeable with the new rubber. After 8 to 10 years tyres are past their best and should be changed. Also it’s always worth checking the dates on new tyres, especially important if they are going on a performance car but even on a run of the mill car you don’t want tyres that have sat on a shelf for a couple of years.
A smell you never forget I can assure you! Possibly a bit bizarre but one of the libraries I visit is within walking distance - 1.5 hours round trip - so I usually walk it if the weather is good. The route goes right past the front of a large Kwik Fit store and that smell, somewhat different to the factory, brings back many memories of people I worked with when I worked in the Tyre and Auto stores. (Firestone's version of Kwik Fit,) Wikipedia has a large section on Firestone which might interest you - type in "Firestone Tyre and Rubber Company" - including quite a big write up on the 500 tyre tread separation problem and then the "notorious" Ford Explorer roll over problem. All makes for quite an interesting read - if, like me, you're into that sort of thing.

Back in the late 60s/early 70s when I worked as a race engineer - European Touring Car Championship - for Firestone, one of the circuits we visited was Brno in Czechoslovakia. It was always an "interesting" trip being as how they were then behind the Iron Curtain. On one occasion the engineers from the tyre companies, ourselves, Goodyear, Dunlop, etc were all invited to hospitality at the Barum tyre plant. It was a most impressive facility, we were treated right royally and a very pleasant time was had by all. In fact their factory was much more modern than much of the old plant we were using at that time in Brentford. Of course we, by then, had a modern automated plant in Wrexham Wales, but that closed in the '70s when Firestone withdrew a lot of stuff, ourselves included, and went back to the US.
 
As you say tyre age is very important especially to anyone who runs a low mileage classic or “Sunday” car. I’ve ditched tyres due to age, even though one pair had a reasonable amount of tread left but the difference in performance is very noticeable with the new rubber. After 8 to 10 years tyres are past their best and should be changed. Also it’s always worth checking the dates on new tyres, especially important if they are going on a performance car but even on a run of the mill car you don’t want tyres that have sat on a shelf for a couple of years.
I've been getting my tyres from a wee mobile tyre fitter for some time now - very convenient because he comes to the house and I can do all my own "spannering" (Jacking the car up and loosening and tightening wheel nuts.) When the Mazda joined the "family fleet" back in the new year it had one nearly new tyre and 3 well worn, but by no means illegal. After she'd - daughter in law - run the car for a few weeks I got the opportunity to check the tyres more closely and decided that these three would be better replaced, they were slightly perished with small cracks in the tread grooves and around the beads. So I rang up Steven and he did me a good deal on the Kormorans. Never heard of them? well neither had I but he said they'd be just fine on her wee runabout - and so they've proved to be. Anyway, if you look closely at the bead area in the picture at the start of this thread, just to the right of the 01AX, you'll see the date stamp 0623. These tyres were fitted to the vehicle on 21st March and rolled out of the factory, as you can see, in week 6 of 2023. They must have more or less rolled straight off the ship, into Steven's van and then been fitted to the Mazda. In fact I keep a close eye on tyre age when I buy and he's always fitted very newly made tyres to all our vehicles - I'm very pleased with his service.

I think that, if appropriately stored, and I think that's a big if, tyres are legally allowed to be sold as "new" up to 5, or maybe 6? years from their date of manufacture. These figures are quoted on a number of big tyre suppliers sites. Personally I want mine "fragrantly fresh" please and wouldn't want one if it was anything like 5 years old.
 
A smell you never forget I can assure you! Possibly a bit bizarre but one of the libraries I visit is within walking distance - 1.5 hours round trip - so I usually walk it if the weather is good. The route goes right past the front of a large Kwik Fit store and that smell, somewhat different to the factory, brings back many memories of people I worked with when I worked in the Tyre and Auto stores. (Firestone's version of Kwik Fit,) Wikipedia has a large section on Firestone which might interest you - type in "Firestone Tyre and Rubber Company" - including quite a big write up on the 500 tyre tread separation problem and then the "notorious" Ford Explorer roll over problem. All makes for quite an interesting read - if, like me, you're into that sort of thing.

Back in the late 60s/early 70s when I worked as a race engineer - European Touring Car Championship - for Firestone, one of the circuits we visited was Brno in Czechoslovakia. It was always an "interesting" trip being as how they were then behind the Iron Curtain. On one occasion the engineers from the tyre companies, ourselves, Goodyear, Dunlop, etc were all invited to hospitality at the Barum tyre plant. It was a most impressive facility, we were treated right royally and a very pleasant time was had by all. In fact their factory was much more modern than much of the old plant we were using at that time in Brentford. Of course we, by then, had a modern automated plant in Wrexham Wales, but that closed in the '70s when Firestone withdrew a lot of stuff, ourselves included, and went back to the US.
Looks like Firestone had quite a history, interesting read, thanks for the heads up.
I didn’t realise they were also into surface to surface systems. I spent some time in my younger days on ship to air systems admittedly a bit later but I’m quite surprised their name didn’t come up at some stage. Obviously we didn’t talk about things across the pond back then.
 
I think that, if appropriately stored, and I think that's a big if, tyres are legally allowed to be sold as "new" up to 5, or maybe 6? years from their date of manufacture. These figures are quoted on a number of big tyre suppliers sites. Personally I want mine "fragrantly fresh" please and wouldn't want one if it was anything like 5 years old.
I got a bit caught out by this when a few years back I bought some tires through one of the online Tire companies, can't remember which one, but went and they fitted them. I did not pay any attention to the Age stamps on the tires at the time and about 4 years later and a global pandemic where the car sat for a few months barely moving the tires had started cracking quite badly alone the edge where the tread meets the tire wall. Thankfully they were just about due replacement again as prior to that I had been doing a lot of miles ~20k a year, so maybe got about 40k out of them, but they were 'young' enough that they should not have been cracking like this, Till I clocked the date stamp on them was for 2015 and we were now in mid 2022 so they had clearly been on some garage's shelf for a very long time before I bought them. I'd probably not given it much thought when they were fitted and assumed they were new.

I now use my little local garage who always order the tires in for me. They are competitive with all the big tire companies like kwikfit without the BS.

I have drummed the "1.6mm across the centre three quarters throughout the entire circumference of the wheel" into my wife's head so she doesn't get ripped off if she ever has to go anywhere for a tire and gets the sharp inhalation of breath and the claim of them all needing replacing because one is worn below 3mm (thats one they've tried on me in the past) or the edges are worn and so they need replacing. Oh great its only the edges and not the center three quarters, Please just replace the tire(s) I am asking you to replace now.
 
I've been getting my tyres from a wee mobile tyre fitter for some time now - very convenient because he comes to the house and I can do all my own "spannering" (Jacking the car up and loosening and tightening wheel nuts.) When the Mazda joined the "family fleet" back in the new year it had one nearly new tyre and 3 well worn, but by no means illegal. After she'd - daughter in law - run the car for a few weeks I got the opportunity to check the tyres more closely and decided that these three would be better replaced, they were slightly perished with small cracks in the tread grooves and around the beads. So I rang up Steven and he did me a good deal on the Kormorans. Never heard of them? well neither had I but he said they'd be just fine on her wee runabout - and so they've proved to be. Anyway, if you look closely at the bead area in the picture at the start of this thread, just to the right of the 01AX, you'll see the date stamp 0623. These tyres were fitted to the vehicle on 21st March and rolled out of the factory, as you can see, in week 6 of 2023. They must have more or less rolled straight off the ship, into Steven's van and then been fitted to the Mazda. In fact I keep a close eye on tyre age when I buy and he's always fitted very newly made tyres to all our vehicles - I'm very pleased with his service.

I think that, if appropriately stored, and I think that's a big if, tyres are legally allowed to be sold as "new" up to 5, or maybe 6? years from their date of manufacture. These figures are quoted on a number of big tyre suppliers sites. Personally I want mine "fragrantly fresh" please and wouldn't want one if it was anything like 5 years old.
I’m with you on the “fragrantly fresh” and 5 years on the shelf no matter how they were stored wouldn‘t fill me with confidence to say the least. I suspect the local tyre fitters that I’ve used for many years would also refuse to fit anything that old anyway.
 
Don't know if I should apologise for resurrecting this thread? but I was fascinated to yesterday see a make of tire I've only seen once before - and that was just last week. Someone in our area must have started stocking them I suspect?

Used to be, in years gone by when I was much younger, that you would commonly see Dunlop, Good year, Firestone, India, Avon etc and some others I forget. Then names I wasn't familiar seemed to appear all of a sudden, Nankang, Barum (a good tyre in my opinion) Churchill, Rovelo, Sailun, Autogreen and many others.

Anyway, the one I saw last week and yesterday was a "Waterfall". Such a strange name I though so I had to look it up and it turns out these are the people who make them: https://www.kocaelilastik.com.tr/ an interesting site I thought and interesting use of the English language/grammer.
 
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