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Hey Steve,

 

You might have touched on this already, if so steer me to where, but can you give a layman's overview of tire construction? Some drawings would be fantastic too.

 

Many terms have been batted around: "tread, void, siping" and it would be cool to know those too.

 

Best,

CF

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Hey Steve,

 

You might have touched on this already, if so steer me to where, but can you give a layman's overview of tire construction? Some drawings would be fantastic too.

 

Many terms have been batted around: "tread, void, siping" and it would be cool to know those too.

 

Best,

CF

 

BASIC TIRE CONSTRUCTION:

 

I'M not going to get to complicated on this one, just the basics. Then when everyone is up to speed we will take it to another level.

 

Below is a basic JLB construction. ( JointLess Band construction) Click on the pic to enlarge it.

 

post-17938-0-72814800-1299210717_thumb.jpg

 

Looking at the image above note the black section on the bottom of the image. This is called the inner liner. It is the rubber on the inside of the tire that holds the air, much like an inner tube would do. When the tire is built, this is the first thing they lay out.

 

The next layer (brown) is the carcass or casing. This tire is a radial, so the fibers are going in 1 direction going radially from left to right. This is what makes a radial tire. A bias ply tire would NOT have the fibers going in this direction (that's another post). These fibers all going in a radial direction, which is the base for the whole tire.

 

The next layer, in darker yellow, is the belt or breaker or band. In this case its a JLB construction. The fibers are going in 1 direction, around the tire (perpendicular to the radial carcass). JLB is wound on the tire much like a string is wound on a spool, from one side to the other. The tire is rotated and a single strand in wound on from one side to the other. That is where the "JointLess" comes from. There is no Joint or overlap, its continuously wound and makes for a very safe tire. It also is what makes the tire zero growth.

 

The next layer, the yellow center section flanked by 2 black sections is the "Tread". This piece of rubber is placed over the belt after all the other parts are in place. It is wrapped around 1 time, then there is a seam where it meets. The seam sticks together during the vulcanizing process in the mold. This tread is meant to wear out when used. It is separate from the construction in that it can wear, or be cut, and as long as the construction is not punctured or cut, the tire will remain intact and hold air. Small road hazards or cuts/punctures are not a problem if they are kept to only this layer. This particular tread is a MultiTread. Which has 3 different sections. The center being a more durable and heat resistant. The sides being higher grip. This section is made at one time in a continuous extrusion. Section are cut at exact length, and later placed on the carcass during the building of the tire.

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Steve,

 

Fantastic stuff, cleared some things up for me.

 

2 questions maybe you could clear this up:

 

What is vulcanizing?

 

The part of tread being cut to fit, and also the extrusion...I didn't quite copy how that all worked, could you explain that a tiny bit more?

 

CF

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What is vulcanizing?

 

CF

 

Correct me me if I'm wrong. It's my understanding that vulcanization is process by which the individual 'bands' of rubber are fused together. The process includes heat (and inside counter-pressure) combined with a curative - most often sulfur. Vulcanization is also responsible for the tire's (or any rubber / polymer item's) tensile strength and pliability.

 

I think the "extrusion" is squeezing 3 lenghts of rubber through a die forming one strip; which is then wrapped around the carcass prior to the molding process.

 

 

The next layer, the yellow center section flanked by 2 black sections is the "Tread". This piece of rubber is placed over the belt after all the other parts are in place. It is wrapped around 1 time, then there is a seam where it meets. The seam sticks together during the vulcanizing process in the mold. This tread is meant to wear out when used. It is separate from the construction in that it can wear, or be cut, and as long as the construction is not punctured or cut, the tire will remain intact and hold air. Small road hazards or cuts/punctures are not a problem if they are kept to only this layer. This particular tread is a MultiTread. Which has 3 different sections. The center being a more durable and heat resistant. The sides being higher grip. This section is made at one time in a continuous extrusion. Section are cut at exact length, and later placed on the carcass during the building of the tire.

 

Ok. Then why does the first part of the tread last longer then that closer to the wear marks?

 

Generic example: (total depth of the sipe - broken into 4 parts)

first quarter = 2k miles

second quarter = 1k miles

thrid quarter = 500 miless

fourth quarter (at the wear mark) = 100 miles.

 

If the entire "Tread" is one strip overlapped onto the construct.... shouldn't it wear evenly throughout the thickness [excluding multiTread "softnesses"]? If the center "harder strip" is the same material as the outer edge, I'm not understanding why the inner tread doesn't wear similarly.... unless the tire has more flex as it looses some of the tread layer, thereby increasing its heat level, and in-turn burning through more tread.

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Steve,

 

Fantastic stuff, cleared some things up for me.

 

2 questions maybe you could clear this up:

 

What is vulcanizing?

 

The part of tread being cut to fit, and also the extrusion...I didn't quite copy how that all worked, could you explain that a tiny bit more?

 

CF

VULCANIZING:

 

Simply put, Vulcanizing is when you get the rubber hot, and it changes into rubber that hold its shape and will bounce back to its original shape after flexing. Imagine "Silly Putty", you can flex it and pull it apart, it feels rubbery but does not hold its shape. Vulcanizing would be if you took that Sully Putty and got it hot for a while and then it turned into an eraser. You could then flex it and it would return to its original shape.

 

That is what is happening when you put the tire in the mold and get it hot for a while. There is a chemical reaction with the heat, rubber and sulfur, which transforms the rubber and makes it into Vulcanized rubber. Without this chemical reaction the rubber would not change form and there would be no tire as we know it.

 

History- Charles Goodyear (1800–1860) invented vulcanization of rubber when he was experimenting, and heated a mixture of rubber and sulfur.

 

Fact - Dunlop and Goodyear are the same company.

 

 

EXTRUSION:

 

It is where the rubber (before vulcanization) is heated up and forced through an extrusion die. Much like you force icing for a cake though a die (held in your hand) and make different shapes. But the shape of the rubber is the width of the tire and about 3-7 mm thick. It comes out of the die in a continuous stream. It is cut to a very exact length (see TREAD below for this concept). It could be 1 compound, or may compounds, depending on how high-tech the extruder is. In the case of the picture in the first post, there are 3 zones, left, right and center, with the left and right zones being one compound (softer) and the center being another compound (harder). Some extruders can handle 7 different zones.

 

 

TREAD:

 

I will do my best to explain without a picture. Imagine a cup, a round drinking cup. If you took a piece of duct tape and wrapped it around the cup, 1 time. If you cut the length of tape to be exactly the right length it would meet exactly where it started. Get this idea? OK, so the cup is the carcass of the tire, the tape is the tread, the splice is where it meets, the thickness of the tape is how thick the tread is. That is my simple way to represent it.

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Ok. Then why does the first part of the tread last longer then that closer to the wear marks?

 

 

That will depend on the compound. Some compounds may be formulated is such a way (not necessarily on purpose) that they wear better when hotter and other compounds wear better when colder.

 

Keeping in mind as the tread gets thinner, it will run cooler (given all other variables stay the same, like lap times, suspension, rider weight, track surface and others). This cooler running tire may have better or worse wear characteristics that it did when new and running hotter.

 

Other variables kick in as well. When the tire runs cooler it may have less grip and thus the lap times may be slower and thus less wear on the tire. Or cooler tire, less grip, more sliding, more wear. it could go either way depending on lots of factors and variables.

 

Not trying to give a no answer, answer, but i have observed it going both ways.

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Great topic and great answers.

Re "as tire gets thinner it will run cooler .... when the tyre gets cooler it may have less grip", is that the reason why a tire has less grip as it gets old? The thread might be gone, but there is still a decent contact amount of rubber making contact with the road - if anything, without the thread there is more rubber making contact (or so it seems to me). Or do other factors come into play?

I recall noticing this when I was a young man, with never enough money for new tyres for my old car. Once the thread was gone, so was the grip - despite the fact that there is actually more rubber in contact with the road.

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Great topic and great answers.

Re "as tire gets thinner it will run cooler .... when the tyre gets cooler it may have less grip", is that the reason why a tire has less grip as it gets old? The thread might be gone, but there is still a decent contact amount of rubber making contact with the road - if anything, without the thread there is more rubber making contact (or so it seems to me). Or do other factors come into play?

I recall noticing this when I was a young man, with never enough money for new tyres for my old car. Once the thread was gone, so was the grip - despite the fact that there is actually more rubber in contact with the road.

 

Thinner tread runs cooler and has less grip.

 

Thicker tread runs hotter and has more grip.

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