Section 1- Tire Basics/Anatomy Flashcards
Tire anatomy
As the only direct connection point between a vehicle and the road surface, tires perform crucial functions:
- support the vehicles weight
- enhance safety by transmitting acceleration, breaking and cornering forces
- absorb road shocks
Obviously we know a tire rolls a vehicle down the road, but it also performs other important functions. A tire has to support the vehicles considerable weight in a safe fashion. It has to transmit the ABC’s: acceleration, breaking and cornering forces. It must also absorb road shocks so the vehicle and passengers can travel safely and comfortably for any period of time over various conditions. Keeping these key functions in mind, let’s take a look at tire anatomy.
Section 1 - Tire Basics
In order to capitalize on all this potential, dealership staff must understand the basics in order to differentiate the many tire types and make appropriate recommendations. For some this may be review, but our experience shows that everybody picks up something new, so let’s begin.
Tire Anatomy Tires consist of 3 major components - tread area - casing or carcass - belt system
Tires consist of three major components- the casing or carcass, the belt system and the tread. Let’s review each one.
Tire Anatomy Casing or carcass Functions: foundation/ strength Two components: - liner - bead
The casing forms the main body of the tire. It’s the foundation in the building of a tire. Like any good foundation, its primary function is to provide support and strength. Some of the strength comes from casing piles that run radially from here to here. Parts of the casing include the liner and the bead.
Tire Anatomy The Liner - covers the inside surface - holds air inside the tire The Bead Area - supports the lower sidewall - forces the edge of the tire against the wheel rim when inflated
The liner is a butyl rubber covering of the inside surface of the tire. It is the only airtight part if the tire. It is the modern equivalent of the tire inner tube that we still see on bicycles and tractor tires. We’ll see later how the liner plays an important part in tire inspection and troubleshooting.
The Bead Area supports the lower sidewall and allows the edge of the tire to seat tightly against the metal rim and keep an airtight seal.
Tire Anatomy Belt system Functions: - strengths/ stabilizes the tread - promotes good handling - maximizes tread life Two Types: - steel belts - nylon belt guard
Next let’s look inside the tire at the belt system. Belts cover the entire face of the tire. They add strength and stability to the tread, allowing good handling and maximum tread life.
They are made of steel or Kevlar. Does anyone know what else Kevlar is used in? Bullet proof vests. So do you think these belts are very strong? Yes you’re right, these belts are very strong, they do not break. You might have heard the term, “broken belt” used to refer a damaged or defective tire. This is high,y unlikely. Belts do separate from the casing though, and we’ll cover that a little later.
Some tires have an dictionary “belt” called a nylon belt guard, which covers the steel belts. A lot of people ask: why are certain tires more expensive? For instance, all Michelin tires have a nylon belt guard. This nylon belt guard shrinks when heated. So when this tire gets rotating, 750 times per mile, and side walls get flexing very fast and create a lot of heat, the nylon then shrinks and adds more stability and control to the tread area.
*for programs who support tire repairs- link to repair standards.
Tire Anatomy The Tread Area Functions: -removes water, mud and snow - traction and handling - heat dissipation Components - Tread blocks - Grooves - Sipes
Moving to the outside of the tire we have the tread area which performs multiple functions.
Read bullets
The tread is made up of three components: the tread blocks, grooves and sipes.
Tire Anatomy
Tread Blocks: Contact the roads, transmit the drivers input to the tires
Grooves: Channel water
Sipes: Squeeze to grip road (traction)
The tread blocks contact the road. Tread blocks are always of different sizes and computer designed on each tire to eliminate harmonics and reduce road noise.
There are two types of grooves: Longitudinal- which channel the water away from the tire and help keep the blocks in contact with the road. And Transverse grooves- which grip mud, snow, and ice and work to channel away these elements.
Sipes are knifelike slits in the tread blocks. Sipes are for traction. They open slightly then close on any bit of ice, rock or snow. Modern winter tires utilize this design over the large tractor-like tread faces once used for improved traction. They look like a standard all-season tire but with hundreds of sipes cut into the tread block.
Tire Anatomy
Three Major Tread Patterns
Symmetric: mirror-image (flexible design, wet weather)
Asymmetric: Differing pattern left to right (cornering, side out indicator on sidewall)
Directional: revolves forward (performance, directional arrow on sidewall
It is helpful to understand that there are three major tread patterns:
Symmetric tires have a mirror image from left to right. The identical design allows for the best flexibility. These can be mounted either side out on the left or right of the car. They can also be rotated to any position as part of regular maintenance.
Asymmetric tires have a different pattern from left to right. Usually this type of tire has one side designed for better cornering. Obviously, this prevents the tire from being mounted either side out.
Directional tires are typically found in the Hugh performance market, but are starting to show up in replacement non-performs r tires as well. These must be mounted to revolve forward. That direction is indicated by an arrow on the sidewall. This design is less flexible in that the tires can only rotate from front to back while remaining on the same side of the vehicle unless dismounted from the rim.
If everyday was warm and sunny, and we always drive on dry smooth pavement: what would be the best tread design for our vehicles?
- All-season
- Performance
- Racing slick (no tread design)
- It wouldn’t matter
Even if you haven’t had much experience with tires, we’ve all seen the different tread designs on TV, print ads, or while shopping around tire displays. Let me ask the group, if everyday was warm sunny, with dry smooth pavement, what would be the best tread design?
Racing slick
This question was in effort to illustrate how all tires are a compromise. Racing slicks are great for dry traction because you have the most rubber making contact with the road. However we must drive in all types of weather. To accommodate for this grooves and sipes are cut into the rubber for the benefit of wet/snow traction but the trade off becomes dry traction.
