LV31 wheels and tyres (2)

LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2) LV31 wheels and tyres (2)

kap all phase & 6/11/03 11:37 am Page 37 Student Workbook LV31 Wheels and Tyres (2) LV31/SWB Student Workbook for Technical Certificates in Light Vehicle Maintenance and Repair MODULE LV31 WHEELS AND TYRES (2) Contents Page Tyre Maintenance: Tyre pressure checks Tread depth and condition Progress check 3 Common Tyre Faults: Exercise Progress check 5 11 Principles of Wheel Balancing: Progress check 12 15 Types of Wheel Bearing: Exercise Exercise Single row deep groove ball bearings Exercise Progress check 16 17 21 24 24 25 Page Types of Driven Rear Hubs: Maintenance of wheel bearings Progress check Wheel bearing faults Progress check 26 27 30 31 33 -1Copyright © Automotive Skills Limited 2003 All Rights Reserved LV31: Wheels and Tyres (2) Issue -2Copyright © Automotive Skills Limited 2003 All Rights Reserved LV31: Wheels and Tyres (2) Issue Tyre Maintenance Tyre maintenance involves three main areas: pressure checks, examination of tread depth and condition and examination of wheel and tyre for damage Tyre pressure checks This picture shows a tyre pressure gauge in use When inflating tyres the vehicle manufacturers’ settings should be adhered to The following should be checked; the pressure must be appropriate for the number of passengers and load carried, there should be no pressure difference between the right hand tyre and the left hand tyre and the pressure difference between the front and rear wheels must always be maintained Failure to ensure this could affect the vehicle’s handling by producing excessive understeer or oversteer Tread depth and condition A simple tyre tread depth gauge in use The law states that there must be a minimum of 1.6mm over the full circumference of the tyre and across a minimum of 75% of the tyre’s width There must be evidence of tread on remaining 25% of the tyre width To assist in assessing tread wear most tyre manufacturers incorporate tread wear indicator bars into the tread of the tyre -3Copyright © Automotive Skills Limited 2003 All Rights Reserved LV31: Wheels and Tyres (2) Issue Progress check Answer the following questions: What are the legal requirements for tyre tread? Give two other tyre maintenance checks that should be carried out: -4Copyright © Automotive Skills Limited 2003 All Rights Reserved LV31: Wheels and Tyres (2) Issue Common Tyre Faults A tyre tread in serviceable condition Exercise Identify any faults with the following tyres by using a highlighter pen: -5Copyright © Automotive Skills Limited 2003 All Rights Reserved LV31: Wheels and Tyres (2) Issue -6Copyright © Automotive Skills Limited 2003 All Rights Reserved LV31: Wheels and Tyres (2) Issue An example of severe “kerbing” which has caused damage to both wheel and tyre, both of which are rendered unserviceable It is not practical to repair the wheel since it is almost impossible to get the rim profile back to its original shape and the use of heat could alter the mechanical properties of the wheel, both of which would have serious implications The above diagrams show examples of abnormal tread wear patterns The wear has been caused by under or over inflation, incorrect wheel alignment, braking faults, wheel imbalance and excessive cornering speeds When faced with the abnormal tread wear patterns shown, the technician should identify the cause of the problem before the tyre is replaced -7Copyright © Automotive Skills Limited 2003 All Rights Reserved LV31: Wheels and Tyres (2) Issue A classic example of regular wear on the shoulders of the tread caused by prolonged running with the tyre under-inflated Right hand diagram shows a classic example of regular wear on the centre of the tread caused by prolonged running with the tyre over-inflated The effects on the tyre tread of excessive camber angle are shown in the next diagram The wear pattern seen in here could also be caused by excessive cornering speed Some vehicles, which have large camber angle settings, may normally show this wear pattern -8Copyright © Automotive Skills Limited 2003 All Rights Reserved LV31: Wheels and Tyres (2) Issue The effect of excessive toe-in of the wheels It produces feathering of the tyre tread Compare this wear pattern with the next illustration, where the wheel alignment has been set with too much toe-out Notice how the feathering faces in the opposite direction As mentioned previously, the cause of the abnormal wear should be rectified before the tyres are changed In the last two cases wheel alignment should be adjusted to the manufacturers’ specification -9Copyright © Automotive Skills Limited 2003 All Rights Reserved LV31: Wheels and Tyres (2) Issue There is no spacer between the bearings so extreme care must be exercised when tightening the nut and locknut The manufacturers’ instructions must be strictly adhered to An example of a driven front axle using taper roller bearings -19Copyright © Automotive Skills Limited 2003 All Rights Reserved LV31: Wheels and Tyres (2) Issue An IRS rear hub using a collapsible spacer between the bearings This ensures the correct bearing pre-load when the nut torque is set to the manufacturers’ figure -20Copyright © Automotive Skills Limited 2003 All Rights Reserved LV31: Wheels and Tyres (2) Issue Exercise Angular contact bearings The following diagrams show the construction and applications of angular contact bearings, both single row and double row This is single row angular contact bearing Draw in the arrows as shown on the slide to show that the bearing can only resist thrust in one direction To overcome this problem single row angular contact bearings are always used in pairs facing in opposite directions Where space is limited in a hub then double row angular contact bearings are used with the inner bearing track split in two to assist with assembly It also enables the bearing to be pre-loaded Angular contact bearings are able to resist large axial loads -21Copyright © Automotive Skills Limited 2003 All Rights Reserved LV31: Wheels and Tyres (2) Issue An example of a driven front hub using a double row angular contact bearing Notice how compact the bearing assembly is Another example of a driven hub using a double row angular contact bearing is shown here -22Copyright © Automotive Skills Limited 2003 All Rights Reserved LV31: Wheels and Tyres (2) Issue The exploded views shown, in the two diagrams above illustrate the details of a typical driven front hub employing this type of bearing The design is simple and compact It is also easily serviced if and when the bearing needs replacing and involves the minimum of dismantling -23Copyright © Automotive Skills Limited 2003 All Rights Reserved LV31: Wheels and Tyres (2) Issue Single row deep groove ball bearings The following diagrams show construction and applications of this type of ball bearing This type of bearing is used where space is at a premium Because of the deep grooves it is able to resist thrust in both directions Exercise Draw in the arrows in this diagram as shown on the slide to show that the bearing can only resist thrust in one direction The most common use of the single row deep groove ball bearing is shown above This is a live axle as used on rear wheel drive pick-ups and light vans -24Copyright © Automotive Skills Limited 2003 All Rights Reserved LV31: Wheels and Tyres (2) Issue Progress check Answer the following questions: Name the three types of wheel bearing: Which one can be used alone? -25Copyright © Automotive Skills Limited 2003 All Rights Reserved LV31: Wheels and Tyres (2) Issue Types of Driven Rear Hubs These come under three headings, semi-floating, three quarter floating and fully floating All axle shafts, or half shafts, are subjected to torsional loads as the drive is transmitted to the wheels but in addition they are subjected to other loads depending on the type of rear hub used • semi-floating - the axle shaft is subjected to shear and bending loads • three-quarter floating - the axle shaft is subjected to bending loads • fully-floating - the axle shaft is only subjected to normal torsional loads A semi-floating hub is shown here This is a simplified diagram to illustrate the position of the single row deep groove ball bearing Notice how the axle shaft has to withstand a shear load next to the hub, and a bending load; this is due to the downward force produced by the weight of the vehicle Compare the last diagram with this one which shows a three quarter floating hub This diagram shows how the single row deep groove ball bearing is fitted on the outside of the axle casing, thus eliminating the shear load on the axle shaft It is still subjected to some bending load in the same way as the semi-floating hub -26Copyright © Automotive Skills Limited 2003 All Rights Reserved LV31: Wheels and Tyres (2) Issue A simple diagram of a fully floating hub The use of two bearings situated on the outside of the axle casing means that bending loads on the axle shaft or half shaft have also been eliminated This type of hub is mandatory on large goods vehicles because of safety reasons If the axle shaft should break then the load carrying ability of the hub is not reduced Maintenance of wheel bearings Little maintenance is required apart from the following checks: • ensure that there is sufficient grease in the cap • check for noise and roughness • check condition of oil seals -27Copyright © Automotive Skills Limited 2003 All Rights Reserved LV31: Wheels and Tyres (2) Issue A cross section through a typical hub oil seal Other maintenance checks on wheel bearings • check end float or axial movement in bearing • carry out other adjustments depending on manufacturers’ instructions Important Some bearings are preloaded using collapsible spacers These spacers should only be used once Other bearings don’t use spacers and are very lightly pre-loaded On no account must the pre-load setting be exceeded The use of a DTI checking wheel bearing end float is shown here Notice how the disc brake caliper has been removed in this case to ensure that an accurate reading is obtained This allows the hub to move without being constricted by the brake pads -28Copyright © Automotive Skills Limited 2003 All Rights Reserved LV31: Wheels and Tyres (2) Issue The end float on a rear hub being checked In this case the brake drum has been removed to ensure that the reading is accurate A torque wrench is being used to set the bearing pre-load -29Copyright © Automotive Skills Limited 2003 All Rights Reserved LV31: Wheels and Tyres (2) Issue Progress check Answer the following: Name the three basic wheel bearing maintenance checks: -30Copyright © Automotive Skills Limited 2003 All Rights Reserved LV31: Wheels and Tyres (2) Issue Wheel bearing faults If lubricant is kept in and water etc kept out the bearings will run for many thousands of kilometres before the surface of balls, or rollers and the bearing tracks begin to suffer wear This wear will show itself in the form of pitting, cracking or scoring of the contact surfaces The effects of wear will be noise, excessive free play, roughness and/or tight spots The photographs on the next pages show examples of worn bearings The above illustrates bearing wear due to the ingress of water and leakage of lubricant from a worn oil seal -31Copyright © Automotive Skills Limited 2003 All Rights Reserved LV31: Wheels and Tyres (2) Issue The photograph above shows surface cracks, score marks and pitting to a taper roller bearing outer track This shows the effects of water and lack of lubricant on the bearing rollers and cage -32Copyright © Automotive Skills Limited 2003 All Rights Reserved LV31: Wheels and Tyres (2) Issue Progress check Answer the following: Name three common wheel bearing faults: -33Copyright © Automotive Skills Limited 2003 All Rights Reserved LV31: Wheels and Tyres (2) Issue ... Skills Limited 2003 All Rights Reserved LV31: Wheels and Tyres (2) Issue -2Copyright © Automotive Skills Limited 2003 All Rights Reserved LV31: Wheels and Tyres (2) Issue Tyre Maintenance Tyre maintenance... Skills Limited 2003 All Rights Reserved LV31: Wheels and Tyres (2) Issue -6Copyright © Automotive Skills Limited 2003 All Rights Reserved LV31: Wheels and Tyres (2) Issue An example of severe “kerbing”... of passengers and load carried, there should be no pressure difference between the right hand tyre and the left hand tyre and the pressure difference between the front and rear wheels must always