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A d v a n c e d A u t o M a i n t e n a n c e |
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Wheels and Tyres Dos and Don’ts... Here are the dos and don’ts of wheels and tyres to help you to manage this vital aspect of your vehicle and that can make all the difference in getting better road handling from your vehicle: When removing a wheel, loosen the wheel nuts before jacking up the vehicle... If a wheel needs to be removed, its wheel nuts should always be loosened before jacking up the vehicle while the wheel is still in contact with the ground. Conversely, when the wheel is put back onto the vehicle, the wheel nuts should only be tightened very firmly hand-tight while the vehicle is still raised off the ground. It is only when the vehicle has been lowered to the ground and the wheel is in contact with the ground that the wheel nuts should be tightened to the torque specified in the owner’s manual, in a crisscross pattern in stages. It’s very difficult to obtain any leverage on the wheel nut while the wheel is raised off the ground because there’s little to hold the wheel in a fixed position. There may be the parking brake to hold it or the automatic transmission being in the ‘Park’ position to hold it (if the vehicle has an automatic transmission), but it’s not good to rely on either of these for holding the wheel. In the case of the automatic transmission being in ‘Park’, it might put a strain on the transmission to attempt to loosen the wheel nuts while the driven wheel (e.g. a front wheel in the case of a front wheel drive vehicle) is raised off the ground. The best way to hold a wheel in a fixed position while loosening its wheel nuts is for the vehicle to be in full contact with the ground so that the weight of the vehicle is bearing down on the wheel in question. With the parking brake on and the automatic transmission in ‘Park’ (if the vehicle has an automatic transmission) to hold the vehicle in place, the weight of the vehicle stops the wheel from moving when its wheel nuts are loosened. When loosening or tightening wheel nuts, loosen them or tighten them in a crisscross pattern in stages... Because wheel nuts are fastened tightly, don’t loosen or tighten one of them fully before loosening or tightening the next one. Simply loosen or tighten each one a bit at a time in a crisscross pattern. This takes longer but it guarantees that no components in the wheel hub assembly or in the disc brake rotor will warp or be put under undue strain. Tighten the wheel nuts to the correct torque with a torque wrench... The owner’s manual for your vehicle will generally specify the appropriate tightening torque for the wheel nuts on your vehicle in foot pounds or Newton metres. If you’re able, it’s a good idea to obtain a torque wrench from your local automotive parts shop or tool outlet so that you can observe this tightening torque when tightening the wheel nuts. A torque wrench is a socket wrench that allows you to select the torque you want to apply when you tighten a fastener such as a bolt or nut. Torque is mostly measured in foot pounds or Newton metres. The higher the torque, the tighter the fastener will be tightened. You select the torque you want to apply on the torque wrench and then proceed to tighten the fastener, such as a wheel nut. When you hear the torque wrench produce an audible ‘click’, you know that the fastener has been tightened to the torque you specified. Kincrome is one company that manufactures high-quality torque wrenches. For tightening wheel nuts, you will need a 1/2 inch drive torque wrench which has a range of about 10 to 150 foot pounds or 14 to 204 Newton metres and costs about $90. A torque wrench is a precision instrument. To ensure that the torque wrench operates accurately and lasts a long time, all of the instructions and precautions included with the torque wrench should be strictly followed. Over-tightening the wheel nuts can damage the disc brake rotors or the wheels themselves... It’s very important not to over-tighten the wheel nuts, hence the desirability of using a torque wrench to ensure that the correct torque is applied. Over-tightening the wheel nuts can lead to the disc brake rotors behind the wheels warping which in turn results in the brake pedal pulsating. It can also damage alloy wheels, which are generally softer and lighter than steel wheels. If you take your vehicle to a mechanic to be serviced, bear the possibility in mind that he or she may over-tighten the wheel nuts on your vehicle when putting the wheels back on the vehicle after he or she finishes repairing it. Professional mechanics are known to often dislike using torque wrenches. They often pride themselves on being able to ‘feel’ the correct torque that needs to be applied to a fastener. While some definitely can apply the correct torque just by ‘feel’ based on their experience and expertise, others only think they can and you need to be aware of the possibility of the mechanic over-tightening the wheel nuts on your vehicle. In addition, mechanics often tighten wheel nuts with air-powered tools which tends to result in over-tightened wheel nuts because these air-powered tools are so powerful. Because it’s important that wheel nuts are tightened in a crisscross manner progressively in stages, after I pick up my vehicle from a mechanic who has worked on it, I generally loosen the wheel nuts of the wheels that were removed by the mechanic to perform the work and then tighten them again progressively in a crisscross manner to the correct torque using a torque wrench. Because of the considerable investment of time and money I’ve made in my vehicle to ensure that it’s set up properly to perform at its peak, I always feel more comfortable doing this rather than just assuming that the mechanic has tightened the wheel nuts correctly. This is especially relevant to my vehicle because it has relatively soft aluminium wheels that can be easily damaged by over-tightening the wheel nuts. Get a wheel alignment every six months... Get a front wheel alignment (and a rear wheel alignment also if the alignment of the rear wheels on your vehicle is adjustable) every six months to avoid uneven wear on the tyres across the width of the tread. Tyres that wear unevenly have a much shorter service life than tyres that wear evenly across the width of the tread, resulting in the need to purchase replacement tyres prematurely. Over the course of six months it’s inevitable that the wheel alignment will go out of adjustment due to the many bumps encountered on the road. You can feel when the front wheels are out of alignment while driving and holding the steering wheel because the vehicle moves less nimbly and more ponderously. In addition, when steering around corners, the vehicle can feel as though it’s fighting you and you have to concentrate harder and apply more effort to steer the vehicle exactly where you want it to go. Probably the easiest way to determine if the wheels are out of alignment is by taking your hands off the steering wheel momentarily when the vehicle is travelling in a straight line on a level road. (You should obviously keep your hands hovering over the steering wheel, ready to take back control after a second or two, to avoid having an accident.) If the vehicle continues travelling in a straight line then the wheel alignment is good. However, if the vehicle veers off to the left or to the right, then the wheels are out of alignment. Replace tyres on the vehicle in left and right pairs... Replace tyres on the vehicle in left and right pairs so that if you fit a new tyre to the front, left wheel of the vehicle, you also fit a new tyre (of the same brand and model) to the front, right wheel of the vehicle. (The same applies to the rear, left and rear, right tyres.) It’s not advisable to have a new tyre fitted on one side of the two front tyres and an old tyre fitted on the other side. The new tyre and the old tyre will have different coefficients of friction with the road surface. That is to say that the new tyre will stick to the road more tenaciously than the old tyre which will not stick so tenaciously and will tend to slip. This difference in attributes of the new and old tyres on the front of the vehicle will lead to poor and even dangerous road handling. As applies to both the front pair of tyres and the rear pair of tyres, the best approach is to have tyres on the left and right sides which are of the same brand and model and which have the same depth of tread on them. Because the left and right tyres on the front of the vehicle will generally wear at the same rate and because the left and right tyres on the rear of the vehicle will generally wear at the same rate, it makes sense to replace the tyres in left and right pairs. In this way, if you find that a tyre has worn down past the tread-wear indicators on, say, the front, left wheel, it is inevitable that the tyre on the front, right wheel will also have worn down past its tread-wear indicators. Both tyres should be replaced with the same brand and model of tyre. Use tyres of the same brand and model on all wheels of the vehicle if possible… Ideally all tyres on the four wheels of the vehicle should be of the same brand and model. This facilitates the use of the spare tyre when needed which should also be of the same brand and model, because it can then be used to replace either a front wheel or a rear wheel if the tyre on either of those wheels gets a puncture or becomes damaged in some way and needs to be taken out of service. If the punctured or damaged tyre can be repaired and returned to its former position, the spare tyre that temporarily replaced it should be taken off the vehicle and returned to its position in the boot as the spare tyre. In the unlikely scenario that the punctured or damaged tyre can’t be repaired so that it must be replaced with a new tyre, the spare tyre should be left on the vehicle and the punctured or damaged tyre should be replaced with a new tyre of the same brand and model as the spare tyre left on the vehicle. For this reason, it’s best if the spare tyre is kept as a new tyre as much as possible, so that it’s always ready to be paired with another new tyre of the same brand and model if such a new tyre is needed to replace a damaged tyre. The good tyre on the opposite side to the spare tyre (which is now in use in place of the damaged tyre) should be moved to the boot as the new spare and replaced with the new tyre. Use tyres of the same brand and model on the left and right pairs of wheels at a minimum… If it’s not possible for the tyres on all four wheels to be of the same brand and model, then, at a minimum, both of the tyres on the front wheels should be of the same brand and model and both of the tyres on the rear wheels should be of the same brand and model. Failure to adhere to this results in poor and even dangerous road handling since tyres of different brands and models have different road handling characteristics. Motor vehicles are symmetrical along their length which means that left and right tyres on the front and rear should be of the same brand and model. Motor vehicles are not symmetrical along their width which means that it’s permissible, although not ideal, for the front and rear tyres to be of different brands and models. The front tyres wear at a different rate to the rear tyres… The front tyres and the rear tyres of a vehicle which is front-wheel drive or rear-wheel drive will not necessarily wear at the same rate because the tyres on the wheels which are driven by the engine and transmission will tend to wear more quickly than the tyres on the wheels that are not driven. On the other hand, on vehicles with front-mounted engines (which is the majority of vehicles), the tyres on the front wheels will tend to wear more quickly than the tyres on the rear wheels because the front wheels tend to carry more weight in the form of the heavy engine and transmission. How this works out for the difference in wear rates between front and rear tyres on a rear-wheel drive vehicle with a front-mounted engine, I’m not sure. I do know that for my vehicle, which has a front-mounted engine and is also front-wheel drive, the front tyres wear out faster than the rear tyres. Always fit new tyres to the front of the vehicle… When the rear tyres on my front wheel drive vehicle wear out, I replace them with a pair of new tyres of the same brand and model but I always put these tyres on the front of the vehicle and move the existing front wheels to the rear of the vehicle. The upshot of this is that whenever I get a pair of new tyres fitted, I move them to the front of the vehicle. This is a good approach for either a front-wheel drive or rear-wheel drive vehicle, because it ensures that the front tyres, which are responsible for steering and the bulk of the braking due to the weight of the front-mounted engine and transmission that they carry, have the most tread on them at all times. The steering and braking, for which the front tyres are responsible, are safety-critical issues, so it makes sense to always put a pair of new tyres on the front and move the existing pair of front tyres to the rear if they haven’t yet worn down past the tread-wear indicators on the tyres. (Naturally it may not be possible to do this if you have set your vehicle up with tyres of a substantially different brand and type with very different handling characteristics on the front and rear of the vehicle.) When fitting new tyres to the wheels, fit new rubber valves also… When getting new tyres fitted to the wheels on your vehicle to replace tyres that have worn down past the tread-wear indicators on the tyres, be sure to ask the mechanic fitting the tyres to remove the existing rubber valve assemblies protruding from the wheels and to replace them with new ones. (The rubber valve assembly protruding from a wheel is what an air hose or foot pump connects to in order to inflate the tyre and increase its air pressure.) By getting new rubber valves fitted, you’ll be greatly reducing the chance that they could fail and leak air during the active service life of the tyres being fitted. If you don’t get new rubber valves fitted, it’s inevitable that they’ll eventually fail and leak air. They’ll fail during the active service life of the tyres on the wheels and cause a lot of inconvenience because it will be necessary to take the vehicle to a tyre workshop and have the rubber valves replaced with new ones. Since these rubber valves are very inexpensive, it makes much more sense to replace them with new ones when new tyres are fitted to the wheels and the vehicle is already at the tyre workshop than to wait for them to eventually fail which will require an extra, inconvenient trip to the tyre workshop to replace them. Logically, it saves a lot of time and inconvenience to replace them with the tyres. It’s worth pondering this point because it represents a principle which also applies to other components of the vehicle. Parts should be replaced before they wear out, not after they wear out. The replacement of parts before they wear out can be scheduled whereas the replacement of parts after they wear out is generally unscheduled and results in inconvenience and an irritating loss of time. |
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Copyright 2016 Andrew Mackinnon. All rights reserved. |
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