Basically everything you might want to know about motorcycle tires but were afraid to ask. A very good writeup, well worth a read.
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http://firebladers.bikenet.gr/articles/ ... ology.html
One of the most important factors of today’s proper bike handling is tires. After all there wouldn’t be such a “rubber” war in the GP scene, if you are from the people who closely watches the GP scene (I think few people reading this article are not watching it) you will have encountered numerous times teams checking on new tires, tire companies trying to retrieve the most out of them…even bike transformations due to them.
Let’s be honest it takes little experience to understand that one of the most important motorcycling aspects is the tire itself. How many times have you complained about the tire not being what you expected, or how many times you have bragged about the cool set of tires you just bought?
Although not a tire expert or even the rider with tons of experience I will try to put down as much valid information I have crossed while searching and discovering.
Tire Construction
Mixing
Tire construction is really complicated opposed to what you see tires may not be mechanical or high tech looking gadgets but are definitely a huge process and years of research.
Although a tire consists of natural rubber (but in really small amounts) there are many more ingredients that finally produce a “synthetic” rubber. The creation of synthetic rubber contrary to natural rubber is necessary to produce the proper characteristics that we demand.
* Carbon black forms a high percentage of the rubber compound. This gives reinforcement and abrasion resistance.
* Sulphur cross-links the rubber molecules in the curing process.
* Accelerators are complex organic compounds which speed up the curing.
* Activators assist the vulcanisation. The main one is zinc oxide.
* Antioxidants prevent sidewall cracking, due to the action of sunlight.
The raw rubber, whether natural or synthetic is called the polymer. The process of combining this with the other ingredients is called mixing. Within the industry, the terms mixture and compound are synonymous. This may seem strange, but the mixing and subsequent curing of the rubber and its ingredients is analogous to baking a cake.
Tire Construction Process
Tire Construction Process
The rubber polymer used to be mixed with the other ingredients on a series of open mills. However, modern tire factories use large internal mixers. The Banbury Internal Mixer manufactured by Farrel is typical of these.
Mill mixing comprised a series of machines with pairs of large steel rollers, rotating with a small gap between them, called a "nip". As the rubber was forced through the nip it provided shearing forces to masticate and work the rubber. Natural rubber required the input of a lot of energy to break it down, so it was first fed into a mill with corrugated grooves cut into it. This is called a "cracker mill". Carbon black for mill mixing was normally obtained as a master batch (pre-mixed with rubber) from an external source, to avoid the handling problems of the fine powder. The curing ingredients are added as late as possible, to avoid the compound curing up.
With Banbury mixing, the process is better controlled. The mixing is done in three or four stages to incorporate the ingredients in a logical order.
The carbon blacks are delivered to the factory in tote bins and are stored in hoppers above the Banbury tower.
The finished rubber compounds are sheeted off and stacked on pallets waiting subsequent processing.
Calendering
The raw carcass materials made of textile or steel are coated with rubber. This is done by passing them through a machine called a calender which has a series of rollers in a stack, normally four. The rollers are called boles. The fabric passes between the middle rollers and rubber is fed from above and below. The thickness of the rubberised fabric is controlled by the gap between the rollers. This gap is called the nip.
The profiled slabs of rubber which go to make up the tread and sidewall of the tire are produced using an extruder. This machine forces the green rubber through a die to give the required shape. After mixing and extruding is finished then the process of actually constructing the tire takes place.
Beads
At each edge of a tire is a wire bead, around which the plies are wrapped, and this bead holds a tire on its rim. In a method similar to calendering, a number of individual, copper-coated wires are wound in a jig, and the resulting matrix-or bead wrap-is rubberized to hold everything together while the tire is being constructed. Even this part of the process can affect a tire's performance, as the shape of the bead wrap determines the fold over of the various plies and how they wrap back into the sidewall.
Assembly
First stage building is assembled on a flat collapsible steel building drum. The tubeless liner is applied, then the body ply which is turned down at the edges of the drum. The steel beads are applied and the liner/ply is turned up. The chafer and sidewall are combined at the extruder. They are applied together as an assembly. The drum collapses and the tire is ready for second stage.
Second stage building has an inflatable bladder mounted on steel rings. The green first stage cover is fitted over the rings and the bladder inflates it, up to a belt guide assembly. The steel belts are applied with their cords crossing at a low angle. Often a nylon zero degree belt is applied above the steel belts, to make the structure work more efficiently.
The tread rubber is then applied. The tread assembly is rolled to consolidate it to the belts and the green cover is detached from the machine.
Curing and Finishing
The green covered are moulded in a curing machine also known as a vulcanizer, or a press.
Cure is often called vulcanization or cross-linking. It is an intermolecular reaction caused by the introduction of chemicals (usually sulphur and zinc oxide or Morfax) which link or tie independent chain molecules together causing the polymer to form molecular networks. These chemical cross-links between polymer chains may be chains of sulphur atoms, single sulphur atoms, carbon to carbon bonds, polyvalent organic radicals, or polyvalent metal ions.
The critical parameters relating to the curing process are:
* The time elapsed before the curing process starts.
* The rate at which the process occurs.
* The extent to which the cross-linking occurs.
There must be sufficient time before the process begins to allow the mixing of all of the ingredients of the rubber compound, the forming of the ultimate product and the molding. Thereafter, the process should be rapid, but controlled. Accelerators (such as zinc oxide) reduce the time required for cure while at the same time resisting premature vulcanization (called scorch). Retarders, on the other hand, inhibit cross-linking or delay cure. It is desirable for a retarder to inhibit cross-linking at processing temperatures, but not at curing temperatures, thus providing more processing time without affecting the cure rate. It is the compounder's task to choose the proper cure system ingredients to accommodate the time required for mixing, forming, molding, and processing the selected polymer into the product or component being manufactured, while at the same time minimizing the time necessary to cure the material to its optimal physical properties. A strong background in chemistry (preferably rubber chemistry) is a highly desirable qualification for a compounder.
The cover is placed over a butyl curing bladder expands the cover to meet the mould surfaces as the press closes. Here the tread pattern is moulded onto the tire. Originally, tire moulds were in two halves. With radial tires, the tread elements are split into segments to avoid distortion to the steel belts as the mould is closing. The sidewall plates are engraved to provide the inscriptions of size etc. on the cured tire.
The tire is cured with high pressure hot water inside the butyl bladder. This has replaced steam as the curing medium, since pure steam at the pressures required would give too high a temperature for an even cure. The mould sidewall assembly is fixed to steel plates which are heated by steam.
Ater curing the tires passes to the finishing department, where they are inspected for defects. After which they are run on balance machines and the heavy spot marked. They then undergo other uniformity controls on a force variation machine. This measures the tires for radial run out, lateral run out and conicity.
Reading the tire codes
190/55ZR17M/CTL 75W
What do this numbers mean?
190 Stands for tire width
55 is the aspect ration (check 180,190,200 Hide and Seek?)
R stand for Radial
17 is the rim diameter in inches
M/C Means for Motorcycle Only
TL stands for Tubeless
75 is the Load Index. The load index (75) is the tire size's assigned numerical value used to compare relative load carrying capabilities. In the case of our example the 75 identifies the tires ability to carry approximately 387 Kilograms.
W is the speed index in our example it means the tire is capable performing at speeds up to 270Km/h.
For more information check the corresponding chart with explanation of its code.
Soft & Hard compounds.
Compounds are often described in terms of their "hardness" or "softness". This does not mean literally how hard the tires are to touch, but describes how the tires behave on the road or the racetrack.
Harder compound tires allow more mileage but offer less grip in relation to soft compound tires which offer less mileage but more grip. What makes a tire soft or hard is specified during the Curing process (check tire construction) and it’s a result of the number of sulphur cross-links between the long rubber molecules.
The hard compound tire has a greater number of cross-links between the long rubber molecules (introduced by Curing). This restricts the length of the rubber molecule that can interact with the road surface. Less interaction between the rubber molecules and the surface means that the tyre has less grip on the road.
Why race tires are not water friendly?
Although many people believe that race tires are not water friendly because of the lack of grooves it is not the only reason.
Lack of grooves does affect tire performance on water (hydroplaning) but another reason of race tire problems in wet conditions is the use of less Silica in the compound. As we described earlier in tire construction there are different ingredients consisting the tire, one of them is Silica. Silica is responsible of traction during wet conditions but is also responsible to provide better heat dispersion, Street tires generally work in a wide range of temperatures compared to race tires, this is achieved with the use of Silica something that race tires do not include in big quantities.
Grip & Traction
Grip = indentation + adhesion
** Article continues...
http://firebladers.bikenet.gr/articles/ ... ology.html
*****************
http://firebladers.bikenet.gr/articles/ ... ology.html
One of the most important factors of today’s proper bike handling is tires. After all there wouldn’t be such a “rubber” war in the GP scene, if you are from the people who closely watches the GP scene (I think few people reading this article are not watching it) you will have encountered numerous times teams checking on new tires, tire companies trying to retrieve the most out of them…even bike transformations due to them.
Let’s be honest it takes little experience to understand that one of the most important motorcycling aspects is the tire itself. How many times have you complained about the tire not being what you expected, or how many times you have bragged about the cool set of tires you just bought?
Although not a tire expert or even the rider with tons of experience I will try to put down as much valid information I have crossed while searching and discovering.
Tire Construction
Mixing
Tire construction is really complicated opposed to what you see tires may not be mechanical or high tech looking gadgets but are definitely a huge process and years of research.
Although a tire consists of natural rubber (but in really small amounts) there are many more ingredients that finally produce a “synthetic” rubber. The creation of synthetic rubber contrary to natural rubber is necessary to produce the proper characteristics that we demand.
* Carbon black forms a high percentage of the rubber compound. This gives reinforcement and abrasion resistance.
* Sulphur cross-links the rubber molecules in the curing process.
* Accelerators are complex organic compounds which speed up the curing.
* Activators assist the vulcanisation. The main one is zinc oxide.
* Antioxidants prevent sidewall cracking, due to the action of sunlight.
The raw rubber, whether natural or synthetic is called the polymer. The process of combining this with the other ingredients is called mixing. Within the industry, the terms mixture and compound are synonymous. This may seem strange, but the mixing and subsequent curing of the rubber and its ingredients is analogous to baking a cake.
Tire Construction Process
Tire Construction Process
The rubber polymer used to be mixed with the other ingredients on a series of open mills. However, modern tire factories use large internal mixers. The Banbury Internal Mixer manufactured by Farrel is typical of these.
Mill mixing comprised a series of machines with pairs of large steel rollers, rotating with a small gap between them, called a "nip". As the rubber was forced through the nip it provided shearing forces to masticate and work the rubber. Natural rubber required the input of a lot of energy to break it down, so it was first fed into a mill with corrugated grooves cut into it. This is called a "cracker mill". Carbon black for mill mixing was normally obtained as a master batch (pre-mixed with rubber) from an external source, to avoid the handling problems of the fine powder. The curing ingredients are added as late as possible, to avoid the compound curing up.
With Banbury mixing, the process is better controlled. The mixing is done in three or four stages to incorporate the ingredients in a logical order.
The carbon blacks are delivered to the factory in tote bins and are stored in hoppers above the Banbury tower.
The finished rubber compounds are sheeted off and stacked on pallets waiting subsequent processing.
Calendering
The raw carcass materials made of textile or steel are coated with rubber. This is done by passing them through a machine called a calender which has a series of rollers in a stack, normally four. The rollers are called boles. The fabric passes between the middle rollers and rubber is fed from above and below. The thickness of the rubberised fabric is controlled by the gap between the rollers. This gap is called the nip.
The profiled slabs of rubber which go to make up the tread and sidewall of the tire are produced using an extruder. This machine forces the green rubber through a die to give the required shape. After mixing and extruding is finished then the process of actually constructing the tire takes place.
Beads
At each edge of a tire is a wire bead, around which the plies are wrapped, and this bead holds a tire on its rim. In a method similar to calendering, a number of individual, copper-coated wires are wound in a jig, and the resulting matrix-or bead wrap-is rubberized to hold everything together while the tire is being constructed. Even this part of the process can affect a tire's performance, as the shape of the bead wrap determines the fold over of the various plies and how they wrap back into the sidewall.
Assembly
First stage building is assembled on a flat collapsible steel building drum. The tubeless liner is applied, then the body ply which is turned down at the edges of the drum. The steel beads are applied and the liner/ply is turned up. The chafer and sidewall are combined at the extruder. They are applied together as an assembly. The drum collapses and the tire is ready for second stage.
Second stage building has an inflatable bladder mounted on steel rings. The green first stage cover is fitted over the rings and the bladder inflates it, up to a belt guide assembly. The steel belts are applied with their cords crossing at a low angle. Often a nylon zero degree belt is applied above the steel belts, to make the structure work more efficiently.
The tread rubber is then applied. The tread assembly is rolled to consolidate it to the belts and the green cover is detached from the machine.
Curing and Finishing
The green covered are moulded in a curing machine also known as a vulcanizer, or a press.
Cure is often called vulcanization or cross-linking. It is an intermolecular reaction caused by the introduction of chemicals (usually sulphur and zinc oxide or Morfax) which link or tie independent chain molecules together causing the polymer to form molecular networks. These chemical cross-links between polymer chains may be chains of sulphur atoms, single sulphur atoms, carbon to carbon bonds, polyvalent organic radicals, or polyvalent metal ions.
The critical parameters relating to the curing process are:
* The time elapsed before the curing process starts.
* The rate at which the process occurs.
* The extent to which the cross-linking occurs.
There must be sufficient time before the process begins to allow the mixing of all of the ingredients of the rubber compound, the forming of the ultimate product and the molding. Thereafter, the process should be rapid, but controlled. Accelerators (such as zinc oxide) reduce the time required for cure while at the same time resisting premature vulcanization (called scorch). Retarders, on the other hand, inhibit cross-linking or delay cure. It is desirable for a retarder to inhibit cross-linking at processing temperatures, but not at curing temperatures, thus providing more processing time without affecting the cure rate. It is the compounder's task to choose the proper cure system ingredients to accommodate the time required for mixing, forming, molding, and processing the selected polymer into the product or component being manufactured, while at the same time minimizing the time necessary to cure the material to its optimal physical properties. A strong background in chemistry (preferably rubber chemistry) is a highly desirable qualification for a compounder.
The cover is placed over a butyl curing bladder expands the cover to meet the mould surfaces as the press closes. Here the tread pattern is moulded onto the tire. Originally, tire moulds were in two halves. With radial tires, the tread elements are split into segments to avoid distortion to the steel belts as the mould is closing. The sidewall plates are engraved to provide the inscriptions of size etc. on the cured tire.
The tire is cured with high pressure hot water inside the butyl bladder. This has replaced steam as the curing medium, since pure steam at the pressures required would give too high a temperature for an even cure. The mould sidewall assembly is fixed to steel plates which are heated by steam.
Ater curing the tires passes to the finishing department, where they are inspected for defects. After which they are run on balance machines and the heavy spot marked. They then undergo other uniformity controls on a force variation machine. This measures the tires for radial run out, lateral run out and conicity.
Reading the tire codes
190/55ZR17M/CTL 75W
What do this numbers mean?
190 Stands for tire width
55 is the aspect ration (check 180,190,200 Hide and Seek?)
R stand for Radial
17 is the rim diameter in inches
M/C Means for Motorcycle Only
TL stands for Tubeless
75 is the Load Index. The load index (75) is the tire size's assigned numerical value used to compare relative load carrying capabilities. In the case of our example the 75 identifies the tires ability to carry approximately 387 Kilograms.
W is the speed index in our example it means the tire is capable performing at speeds up to 270Km/h.
For more information check the corresponding chart with explanation of its code.
Soft & Hard compounds.
Compounds are often described in terms of their "hardness" or "softness". This does not mean literally how hard the tires are to touch, but describes how the tires behave on the road or the racetrack.
Harder compound tires allow more mileage but offer less grip in relation to soft compound tires which offer less mileage but more grip. What makes a tire soft or hard is specified during the Curing process (check tire construction) and it’s a result of the number of sulphur cross-links between the long rubber molecules.
The hard compound tire has a greater number of cross-links between the long rubber molecules (introduced by Curing). This restricts the length of the rubber molecule that can interact with the road surface. Less interaction between the rubber molecules and the surface means that the tyre has less grip on the road.
Why race tires are not water friendly?
Although many people believe that race tires are not water friendly because of the lack of grooves it is not the only reason.
Lack of grooves does affect tire performance on water (hydroplaning) but another reason of race tire problems in wet conditions is the use of less Silica in the compound. As we described earlier in tire construction there are different ingredients consisting the tire, one of them is Silica. Silica is responsible of traction during wet conditions but is also responsible to provide better heat dispersion, Street tires generally work in a wide range of temperatures compared to race tires, this is achieved with the use of Silica something that race tires do not include in big quantities.
Grip & Traction
Grip = indentation + adhesion
** Article continues...
http://firebladers.bikenet.gr/articles/ ... ology.html
