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Straight Talking
Classic American issue 180
When we left you last time, we did so with talk of alignment and terms such as ‘toe in’ and ‘toe out’ whizzing through your head. We also mentioned that your steering alignment could not be correctly set-up if there were any damaged or worn parts within the system. This time we want to look a little deeper in to the problems of worn steering components and also delve further in to the subject of steering geometry, this time looking at ‘caster’ and ‘camber’. Before you ask, NO, these are not star constellations and we do not need to seek the help of Patrick Moore to understand them. These are, however, critical and often little understood measurements within our steering geometry set-up. If your caster and camber angles are not set correctly, all manner of problems can occur. These include the vehicle pulling to one side, excessive tyre wear and wheel alignment problems. So if you have a problem with you car wandering, and we don’t mean it trying to chat up the car next door, or if you find the steering just doesn’t feel right then read on we may have the cure.

So to start let’s ask the following question: What items that are likely to wear out in our steering system? The simplest answer to this is anything that moves. However, this may seem a little vague. To clarify things it may be better to say any component that has a moving part. So, ball joints for example, or any steering component that has a ball type joint as part of its construction could be classed as wearable. However, components such as drag links that simply have holes in them to take the ball joints of other component parts are normally classed as a non-wear items. On older vehicles that have kingpin set-ups, the kingpins themselves are also a wearable item and should be checked regularly. Modern innovations such as grease points, see fig 1, on steering joints and ball joints have allowed us, to a certain degree, to extend the longevity your steering components. Of course you actually have to make the effort to make greasing these joints part of your regular vehicle servicing, A in fig 2. You do of course need to use a good quality, high temperature grease. So the joints you should make part of a regular check are upper and lower ball joints and inner and outer track rod ends. On top of these also check any joints you may have in the pitman arm, idler arm and centre or drag link. As we always try to point out, spending a little time performing these regular checks now can save you a lot of time and money later.

Fig 1.

Fig 2.
If we look at the idler arms from older vehicles, some of these may have a bushing where the two halves of the idler arm join, see fig 3. This bushing can also wear causing steering alignment problems. Therefore this bush should be made part of your regular check. You should be aware that a lot of steering component manufacturers are no longer making the replacement bushes for this type of idler arm. The good news, however, is that most of these companies are now making upgraded replacement idler arms for certain applications. This is something you may want to check, with your parts supplier, if you feel your idler bush needs attention. Replacing your current idler arm with a new assembly, which is serviceable, will again save you time and money later.

With all this talk of worn joints and bushes it is easy to forget that sometimes it is the smallest and simplest of things that cause the largest problems. You may of noticed, whilst checking your steering components, small rubber dust covers, or boots, on most of the ball type joints, see fig 4. BIG DEAL we hear most of you saying, however, most people underestimate the importance of our little rubber friends. If these are split or damaged in any way they will allow moisture in to the joint. This could be from rain, off the road or simply condensation it doesn’t really matter, once water has entered the joint the problems have already begun.

Fig 3.

Fig 4.
Obviously corrosion is the biggest issue, especially if the vehicle is not used on a regular basis. Once the corrosion has set in then the joint can be considered unrepairable and should be replaced. Whilst there are some parts people out there supplying replacement boots, we feel that once you have discovered a damaged boot, damage to he joint itself may have already occurred. The boots shown in fig 5 have been neglected for some time, allowing dirt and moisture to do its job and ruin the joints. So to save false economy we recommend replacing the joint as a whole. Whilst this may be a little more expensive initially it will potentially save on problems later on.

As a parallel to this dust boot problem, those of you with a rack system should regularly check the condition of the rubber gaiters that protect the ends of the steering rack. Again if these are damaged in anyway they can allow moisture to enter the end of the rack, causing all manner of problems. If you find you have any splits or tears in the gaiter you should have the rack checked for damage. Any problems usually result from moisture entering and corroding the rack tube or dirt and grit entering the tube and causing damage to the rack seals. If everything is given a clean bill of health then just replace the gaiters, see fig 6. Worse case scenario is that you may have to replace the entire rack, however, damage is usually confined to the inner track rods.

Fig 5.

Fig 6.
Moving away from ball joints, gaiters and boots we are going to take a look at one of the most important and yet one of the most neglected components in the steering system, the steering coupling. This is, on most vehicles, either a reinforced rubber block, shown as A in fig 7, or a reinforced rubber disc that fits between the end of the steering column and the top of the steering box or rack, see fig 8. A lot of vehicle manufacturers have replaced the rubber component on more modern applications with a universal joint set-up. Because of the amount of stress this item is under, it should be checked regularly, especially if you have the rubber type coupling.

Fig 7

Fig 8
Because this coupling plays such an important role in the steering system, if you see any signs of damage such as the disc becoming oil soaked and soft or split the coupling should be replaced immediately, see fig 9. Unfortunately one size does not fit all, and when you call your parts supplier for a replacement you may find that they require some measurements from the old coupling, especially if it is the disc type. Firstly, they will probably ask for an overall diameter of the disc, measurement 'C' in fig 10. Secondly they will need the measurements between the bolt hole centres. These are shown as measurements 'A' red to red and 'B' blue to blue in fig 10. Armed with this information your supplier should have no trouble providing the correct disc.

Fig 9

Fig 10
As we move through our steering system it is time to become familiar with some new terms. We did mention these at the beginning of this article, the caster and the camber, and no these are not cooking ingredients or rivers. To begin with let’s see if we can get a basic understanding of each term and the problems we can expect to see if we are having trouble with either the caster or camber angles. Let us start with the caster. As mentioned last time, when you steer your vehicle the front wheels turn on pivot points attached to the vehicle's suspension. On modern vehicles this is usually a ball joint set-up, and on earlier vehicles kingpins. The caster angle is measured in degrees and is the amount that the upper pivot points lean towards the front or rear of the vehicle when viewed from the side, see fig 11. The caster if often referred to as being positive when the top of the pivot is leaning toward the rear of the vehicle, toward A in fig 11 or towards the red in fig 12. It is said to be negative when the top of the pivot is leaning toward the front of the vehicle, B in fig 11 or towards the blue in fig 12.

Fig 11

Fig 12
If your caster is out of adjustment then you are likely to suffer problems when you try to have the vehicles wheel alignment or tracking done. For example if the caster angle is different on each side of the vehicle it will tend to pull to the side with the less positive caster angle. If you find that your vehicle has extremely light steering, wants to wander and is difficult to keep in a straight line, then it is possible that the caster, whilst equal on both sides of the vehicle, maybe too negative. Almost the opposite can be said if the caster angle is too positive. The steering will be very heavy and may be likely to kick at the slightest bump.

Fig 13
IProbably the easiest way to understand the caster angle is to look at the wheels on a shopping trolley, see fig 13. Whilst the pivot point of the trolley wheel is not at an angle its line does intersect the ground ahead of the contact area of the wheel. Whilst the wheel is behind the pivot where its line contacts the ground it is said to have positive caster. Now try to imagine pushing this trolley and keep the wheel ahead of the pivot point. The wheel will constantly try to rotate to being behind the pivot point. This is also what happens on a car or truck when the caster angle is set too far negative. It is this that can cause problems with wheel alignment. It should be noted that on many front wheel drive vehicles the caster angle cannot be adjusted. So if there is a problem with caster here, it is more likely that something is worn or damaged and will either require repair or replacement. It should also be noted that any problems with the caster angle have very little affect on tyre wear.

Now let us turn our attention to the subject of the camber angle. This angle is also measured in degrees. It is the amount the wheels lean in or out from the vehicle when viewed from the front or rear. For example if the top of the wheel is leaning away from the centre line of the vehicle, towards B in fig 14 and towards the red in fig 15, this is said to be a positive camber angle. However, if the top of the wheel is leaning towards the centre line of the vehicle, towards the A in fig 14 and towards the blue in fig 15, we have what is known as a negative camber angle.

Fig 14

Fig 15
Unlike the caster angle, if the camber angle is out of adjustment then this will have a detrimental affect on tyre wear, see fig 16, causing a tyre to wear prematurely on one side of the tread. So if the vehicles camber angle is set too negative this will cause excessive tyre wear on the inside edge of the tyre.
Obviously, if the camber is set too positive the wear will be excessive on the outside edge of the tread. The vehicle will tend to pull to one side if the camber angles a set differently on each side of the vehicle. The pull will be to the side that has the more positive camber. Again many front wheel drive vehicles have set-ups where the camber angle cannot be adjusted. If this is the case with your vehicle and you have a problem with the camber angle, once again check for worn or damaged parts. On most vehicles both the caster and camber angles are adjusted using small metal shims, see fig 17. These are of various thicknesses allowing varying degrees of adjustment. For example, the camber angle is usually adjusted by adding or removing these small shims behind the upper control arm, thus allowing the top of the wheel to move closer or further away from the centre line of the vehicle.

Fig 16

Fig 17
The positioning of the shims can bee seen in fig 18 at point B, also shown in this picture is the position of the steering coupling disc, shown at point A.
.....................................Fig 18

There is one final term, which we have left till last, which is the Steering Axis Inclination (SAI). This is a measurement in degrees that forms part of the calculated, but not measurable, camber angle. This is not adjustable but instead is actually part of the fixed design of the vehicle. It should be noted that SAI is usually referred to as kingpin inclination on older cars and trucks that use kingpins instead of ball joints. It is the SAI that causes the front of the vehicle to lift slightly when you turn the wheels away from the ahead position. Because of this the weight of the vehicle causes the wheels to centre themselves, if you release the steering wheel after you make a turn. Again if the SAI is different from side to side on the vehicle it can cause the vehicle to pull to one side at slow speeds. Because the SAI is not adjustable the only way it can be incorrect is due to damaged or worn parts. These would obviously have to be repaired or replaced to correct the problem. Some wheel alignment machines are able to diagnose if a vehicles problem lies with the SAI or the camber angle. If you suspect a problem with the SAI, then finding a wheel alignment company with this type of machine has obvious benefits.

So what have we learnt here? Nothing we hear you say! Well if nothing else we hope you know that it is worth checking out our steering components on a regular basis, and where appropriate treating them to a good greasing. As we have tried to point out on many occasions, prevention is always better than cure. It’s usually cheaper too. If you are experiencing problems with your steering, such as a pull to one side, vibrations or knocking. Try getting the steering alignment checked out, if this makes very little or no difference then at least you now know where to start looking to help solve the problem. Have the caster and camber angles checked, if they are not adjustable on your vehicle then have the steering components checked for signs of wear or damage. Hopefully this will have you up and running in no time or at leased in a straight line! Please remember that if you do require any of the parts, mentioned within these articles, as always they can be obtained from Ultimate Spares of America or any of the other excellent suppliers found within the pages of this fine publication.