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unit 3 wheels and tyre.pptx
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- 2. Introduction Functions • Supports theload on vehicles • Act as the primary suspension, cushioning the vehicle from effects of rough surface. • Allows the wheels to steer • Helps to get best acceleration • Provide frictional contact with the road surface which allows the driving wheels to move the vehicle • Tyres allow braking to slow or stop the vehicle
- 3. Properties of tyres •Non-skidding: – The tyre should have good grip so that it can overcome skidding. • Noise resistant: – There should be minimum noise from tyre during driving. • Optimum Load carrying capacity: – The tyre size and material should be selected in such a way that it can carry vehicle load and withstand with fluctuating stress during revolution. • Minimum power consumption: – Tyre transmits power from engine to road so there should be minimum power loss in tyre to get better efficiency. • Uniform wear: – The wear around the tyre should be uniform so that there is no issue of unbalancing. • Should be well balanced: – The weight and dimensions of all tyre are such that, that it is dynamically balanced. • Satisfactory cushioning: – The tyre should have good shock absorbing property so that it can absorb vibrations by road to provide cushioning effect.
- 4. Terminology • Steel Wheels– Most popular design. Very strong and cheap to produce. • Alloy Wheels – Attractive and light weight, but expensive and difficult to clean. • Spoked Wheels – Used on older vehicles. Cannot be fitted with tubeless tyres. • Divided rims – Rims are made in two halves which are bolted together, (rims must never be separated while the tyre is inflated) • Split rims –Tyre is held in place by a large circlip • Plies – Layers of strong fabric which are built up to give the tyre its strength and shape • Bead – loops of steel which are the anchor point for the plies • Cross Ply Tyre – Main plies of the tyre run at an angle (45 degrees) from one bead to the other • Radial Ply Tyre – Main plies of the tyre run at 90 degrees from one bead to the other • Tread – Rubber pattern. Provides grip with the road surface and assists in clearing water away • Side Wall – Connects the beads to the tread of the tyre
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- 6. 1. Belts: Theseare rubber-coated layers of rayon, Steel fiberglass and other materials which are located in mid of the tread and plies, across at angles, which hold the plies in place. It provides resistance to punctures and help treads to in contact with the road. 2. Sipes: These are special kind treads within the tread which improves tractive effort on different road surfaces. 3. Tread: It is the portion of the tire that comes in directly contact with the road. It should have higher strength and good heat dissipation property for good life of tyre. 4. Grooves: It is the spaces provided on the outer layer of tyre which comes in contact with road. It provides space for water to flow and friction. 5. Shoulder: It is the outer edge of the tread which wraps into the sidewall area. 6. Sidewall: It is the portion of tyre which is exposed to environment and not come in contact with road . It protects cord plies. it is also used to feature tyre markings and information such as tyre size and type. 7. Inner Liner: It is the innermost layer of a tubeless tyre. It prevents the flow of air from inside to outside and vice versa. Parts
- 7. Carbon black addsstrength and abrasion resistance, while protecting rubber against UV light. During curing, sulphur links rubber molecules together, adding strength, and giving the rubber resistance to both heat and cold. Zinc stearate Small amounts of zinc stearate and waxes help control curing rate, prevent oxidation and make rubber easier to process. Accelerators are used to control the cure rate, so different types of rubber can cure fully – in same amount of time. Antioxidants and antiozonants are added to rubber to fight degradation by oxygen and ozone, which can shorten the life of tyres. C O M P O U N D S
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- 10. Bias Ply TyreConstruction • One of the oldest design • Several textile plies are laid across each other, running from bead to bead in alternate directions • Number of plies depends on the size of the tyre and the load it has to carry • Same number of plies is used on the crown and the sidewalls • Plies run at an angle from bead to bead • Does not use belts • Allows body of the tyre to flex easily • Improved cushioning, hence smooth ride on rough roads • Weakness: Reduced traction at high speeds and increase rolling resistance
- 11. Belted Bias TyreConstruction • Bias ply tyres with belts added to increase tread stiffness. • Belts do not run around the sidewalls, they lay under the tread area only • Belts and plies run at different angles • Offers some reduction in rolling resistance over a bias ply tire • Provides smooth ride and good traction
- 12. Radial Ply TyreConstruction • Plies run straight across from bead to bead. • Has a very flexible sidewall and a stiff tread, giving it a very stable footprint • Consist of a carcass ply formed by textile arcs running from one bead to the other. • Each ply is laid at an angle of 90 degrees to the direction the tyre rolling • At the top of the tyre crown (under the tread), a belt made up of several plies reinforced with metal wire is laid. • These crown plies, laid one on top of the other, overlap at an angle determined by the type of the tyre.
- 13. Advantages of RadialPly Tyres • Side walls can bend easily, its shock absorbing capacity is 25% more than bias ply or cross ply. • Lower rolling resistance and hysteresis loss leads to less fuel consumption • Longer tread life because of less heat build in tyre. • Breaking efficiency on wet roads is better because of greater sidewall flexibility and tread stiffness. • Better steering characteristics. • While taking turns it has less tendency to distort and lift off the road from one side. • Larger resistance to punctures ,cuts and impacts in the tread area.
- 14. Bias contact patchRadial contact patch
- 15. Non-Directional Tyres Uniform grooves Canrun in any direction Unidirectional Tyres Grooves are in one direction Direction of rotation is clearly marked
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- 17. Advantages of tubelesstyres • Lesser unsprung weight. • Better cooling • Lesser rolling resistance • Comfortable ride • Slower leakage of air • Simpler assembly • Improved safety
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- 21. Load Rating Load Index Load (Kilograms) Load Index Load (Kilograms) 71 34591 615 72 355 92 630 73 365 93 650 74 375 94 670 75 387 95 690 76 400 96 710 77 412 97 730 78 425 98 750 79 437 99 775 80 450 100 800 81 462 101 825 82 475 102 850 83 487 103 875
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- 23. Feathering • Improper alignment(TOE). •Worn or damaged steering/ suspension parts. • Hard cornering Cupping •Worn or damaged steering or suspension parts. •Improper balancing. One Edge •Improper alignment (CAMBER). •Worn or damaged steering or suspension parts Tyre problems
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- 27. Tread Wear Markings Treadwear indicator Wear Measuring tool Coin method
- 28. Nitrogen in Tyres •Makes up around 80 percent of the air • Dry inert gas. It is less reactive than oxygen. • Leaks out of the sidewall three times slower then oxygen. • Oxygen oxidizes the rubber in the sidewall. • Pumped into tyres in a pure form, hence it does not contain moisture found in compressed ambient air which causes rusting of steel rims. • The result is that all materials that come into contact with the compressed gas inside the tyre are less subject to oxidation corrosion
- 29. WHEELS • Wheels alongwith the tyre has to take the vehicle load, provide a cushioning effect and cope with the steering control. • Various requirement of an automobile requirement are: 1. Strong enough to perform the above functions. 2. Balanced both statically and dynamically. 3. Possible to remove or stand the vehicle wheel easily. 4. As lightest as possible so that the un-sprung weight is least. 5. Easy to clean, easy to wash and be of good quality. 6. Should not deteriorate with age and weathering. If material is vulnerable to corrosion, must be given suitable protective treatment. 7. must be of maximum strength to take the weight road shocks, driving torque and must be able to compensate all sorts of load varying in magnitude and direction. 8. must be strong enough to resist local deformation or when it hits a road kerb or any other obstacle.
- 30. Wheel - Basics Pilotbore fits to the hub. • Most standard wheels are made of steel. • Some vehicles are fitted with alloy wheels that are made of magnesium or aluminum • The rim holds the tyre. • Well of the wheel allows the tyre to be removed and refitted • Centre section is welded to the rim Centre mounting section Rim
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- 32. Valve Stems andCores Functions – Retains air, allows inflation and deflation. Rubber stem of the valve is pulled into the wheel. Valve core contains a spring loaded air valve insert. The valve core also has a sealing washer and a seat washer. Valve cap keeps out dust and helps keep air in. Valve caps Sealing washer Seat washer Valve stem Valve core Tyre pressures must only be checked and adjusted when the tyre is cold
- 33. Taper on thewheel nuts secures and centers the wheel. Wheel studs usually have a right-hand thread. If it is a left-hand thread, it can be marked with “L”. Metric threads are marked with “M” or METRIC. Wheel studs press through the hub or axle flange. Wheel Fixings Wheel studs and nuts attach the wheel to the hub. Taper Wheel mounting Hub flange
- 34. Torque wrench Wheel Nut Torque Correcttorque of wheel fixing is vital for all vehicles, and nearly all require the use of a torque wrench. Excessive torque can lead to wheel or hub distortion, causing runout and vibration. Low torque may allow wheel nuts to work loose and wheels to come off. Nuts should always be tightened in a diagonal pattern.
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- 36. • Direction orspeed change relies on friction between the tyres and the road surface. • Grooves of a rubber tyre are designed to disperse water from under the tyre, providing high friction even in wet conditions. • Aquaplaning occurs when a tyre encounters more water than it can dissipate • Steering appears light as if we are driving with wheels in air • Water pressure in front of the wheel makes a wedge of water under the leading edge of the tyre, causing it to lift from the road. • This loss of traction causes the wheels to slip and prevents the vehicle from responding to steering, braking or accelerating. As a result, the vehicle can go out of control, start to skid or spin. • Risk of aquaplaning increases with the depth of standing water • If multiple tyres aquaplane, the vehicle loses directional control and slide until it either collides with an obstacle, or slows down so that friction is regained. Aquaplaning (Hydroplaning)
- 37. • Tyre treadwear: Worn tyres will aquaplane more easily due to lack of tread depth. • Tyre inflation pressure: Under inflation enhances aquaplaning • Tyre tread aspect ratio: Longer and thinner the contact patch, less likely a tyre is of aquaplaning. (Small diameter and wide tyres are more prone to aquaplaning) • Vehicle weight: More weight on a properly inflated tyre increases the contact patch. Weight can have the opposite effect if the tyre is underinflated. • Vehicle type: Combination vehicles like semi-trailers are more likely to experience uneven aquaplaning caused by uneven weight distribution SOLUTION: If aquaplaning is encountered (steering feels disconnected), DO NOT brake, accelerate, or steer the vehicle. Allow the speed to reduce on its own Aquaplaning (Hydroplaning)
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