In the Panda '03 to '12 section I have been following and contributing to a very interesting thread "weird steering" in which I threatened to wheel out my home made tracking gauge. So, for your delectation and edification, here we go!

First thing to say is that we are talking only of front wheel "Toe" measurement/adjustment here. You may have heard it referred to as wheel alignment? Wheel alignment commonly includes the Toe setting, Camber angle and King Pin Inclination (a carry over from when vehicles had "King Pins") A proper wheel alignment procedure is complicated and only the brave, or incurably optimistic, would attempt to do it themselves! Find a specialist with a full laser aligning setup for this if I were you. But Toe settings can be quite accurately checked with a number of commercially available tools - try You Tube for some very interesting attempts. This is my attempt!

Prior to this there were two working prototypes which finally refined down to this one and, although it looks ridiculously simple and has no "bells or whistles" it has served me well for over 30 years. I use it on all the "family fleet vehicles" with great success.



Here it is disassembled. The two main horizontal tubes were pieces of steel pipe off cut left over from the steam heating system at my work when it was overhauled. (taken with my boss's permission) the larger diameter is about 1" od. The smaller about 3/4" od. These are very substantial pipes with a sidewall thickness of about 1/8". The smaller tube is a very close sliding fit inside the larger. I chose them for their rigidity, close sliding fit, and 'cos they were free! At each end there is tubing (steel electrical conduit) bent up at a little over 90 degrees with stops brazed to their ends such that the face of the stop is at 90 degrees to the main sliding tubes. The larger diameter tube, on the right in the picture, has a two legged foot which fits over it incorporating a locking turn screw allowing for adjustment (explanation to come) and the smaller tube, on the left, has a "pointer" on a sliding collar with locking turn screw allowing for adjustment (explanation to come)



Put it all together and you've got what you see in the first picture. The tool is readied for action by applying a length of masking tape to the left end of the large diameter sliding tube. By the way the sliding tubes are lightly greased to facilitate smooth use.

I'm primarily describing how my tool works in this description, so this is not attempting to describe how to adjust toe settings as such, but it is important to say that for this exercise to be meaningful a very thorough check of all the steering joints, suspension bushes and components, wheel bearings etc must be undertaken before starting as wear, excess movement or damage (ie a bent suspension arm) will make a nonsense of it. One thing many people miss though, and I've seen this many times where untrained or unspecialised staff are involved, is to check whether the wheel rims are "true" by which I mean are the rims undamaged. Damaged rims are common due to "Kerbing" and if a rim does not run "true" then you've no hope of doing this job accurately. Some say that readings can be taken from the tyre wall and they can but I don't think it's so accurate due to the curvature of the sidewall, compliance of the rubber and relatively uneven nature of the sidewall. To check this jack the car up so the wheel is just clear of the ground and can be rotated easily (so no gear selected. You did chock a rear wheel didn't you?) you need a fixed point placed very close to the rim so you can observe the gap between the rim and pointer as you rotate the wheel through a full revolution. I used a rule steadied on an axle stand and you'll need the wheel trim off too.



I like to mark the parts of the rim which do not rotate true with a chalk.



Now I know I cant use anywhere with the white chalk as a reference point so I will place it at either the top or bottom when doing my measurements as they need to be taken at 3 and 9 o'clock. Now go round and do the same to the other front wheel. Now let the car back down onto its wheels and run the car back and forwards over a few yards to settle the suspension back fully to it's normal running condition. Finish up by going forward and don't let the car run back as you want any forces acting on the suspension when traveling forward to be prevalent. Check also that none of your white chalk marks are at 3 or 9 o'clock. If you need to adjust the position slightly remember to only go forward! Oh yes, you need a nice surface to be doing this on too!

Now take the tracking tool and, using the adjustable foot, set it up so it's level with the center of the axle nut and lock off the turn screw. This must not now be loosened for the rest of the operation!



We now need a way of setting the stop on the other end to the same working height (this is critical as failing to make measurements at the same height will be meaningless due to the wheel camber.) This is very simple. A piece of wood cut to the same length does the job grand!



Now position the entire tool across the front of the car



with the stop on the end with the locked up foot against the front edge of the rim of the NSF wheel



and the stop on the free arm, now supported at the correct height by our piece of cut wood, against the front edge of the rim of the OSF wheel



Check carefully that that the stops are fully in contact with the wheel rims on both sides and now slide the adjustable pointer over the piece of masking tape you previously stuck to the large diameter slide tube and lock up its turn screw. this also must not now move for the rest of the operation. One last check to make sure the stops are snug against the wheel rims and, taking a sharp pencil, hold it at right angles to the large diameter tube (to avoid parallax errors) scribe a line against the pointer on the masking tape.



Now slide the whole tool under the car behind the front wheels and repeat the setup against the back of the rims. Making sure the height of the free end is correct using the wooden distance piece and that the stops are snug against the rims





Take the tool out from under the car and have a look at the pencil marks





The first mark I made, with the tool positioned in front of the wheels, is the mark on the right. You will see that there is a small distance (it's actually just under 3mm) to the second mark on it's left. Think about this for a minute. Ok this means the front edges of the two wheels are just under 3mm closer together than the back edges. So the front wheels are not rolling down the road parallel to one another but are "snowplowing" that is "Toed In". Mr Haynes tells me the ideal setting is parallel with a very small allowance of error, but not 3mm. So this explains why my front tyres are exhibiting the signs of too much toe in which I observed in the "weird steering" post. Correcting this is, I think, another story for another day as I'm going quite cross eyed after all this.

Here's a wee puzzle though, just to finish up with. When I removed the wheel studs off to get rid of the wheel trims I "lost" two of them for about a couple of minutes. Can you spot them?

oops! Fifth picture down should be

If you are struggling with distorted rims, and I certainly have with some of the old bangers I've run around in over the years, there are a few "dodges" you can try.
1. You can eliminate the discrepancy by measuring on the same spot on the rim. When you set up to take the first reading, mark the rim or tyre right next to the rim, exactly opposite where the stop ends are in contact on both wheels. Now roll the car FORWARD by exactly half a wheel revolution and take your second set of readings with the stop ends exactly on the marks you first made. Because you are measuring on exactly the same bit of rim any discrepancy in the wheel becomes irrelevant! In practice this method actually works quite well on a billiard table type surface. If, like me, you are in your drive or at the kerbside it's more difficult.
2. If you have another good wheel on the car, often the OSR because it tends to get kerbed less, just swop it over with the poor wheel whilst you take the readings. Of course you still need to check it's OK after you've swopped it!
3. Sometimes, because it's usually the very edge of the rim which gets damaged, you can use the bit where the tyre bead seats. That's the bit with the white chalk on it in my picture. But you still need to check it for trueness (is that a word?). I find this is often a good place to use.

Finally. Anyone had experience of the Gunson Trakrite roll over tool? I really like the look of it. In particular the fact that it works by detecting whether any scrub is taking place regardless of what you might "think" you've got your wheels set up at! It probably costs about what one adjustment might cost at a large tyre retailer and it's been around (in a couple of iterations I think) for quite a few years now so maybe actually works?
So, anyone used one or seen one used? Any good?
Regards
Jock

Pugglt Auld Jock said:

If you are struggling with distorted rims, and I certainly have with some of the old bangers I've run around in over the years, there are a few "dodges" you can try.
1. You can eliminate the discrepancy by measuring on the same spot on the rim. When you set up to take the first reading, mark the rim or tyre right next to the rim, exactly opposite where the stop ends are in contact on both wheels. Now roll the car FORWARD by exactly half a wheel revolution and take your second set of readings with the stop ends exactly on the marks you first made. Because you are measuring on exactly the same bit of rim any discrepancy in the wheel becomes irrelevant! In practice this method actually works quite well on a billiard table type surface. If, like me, you are in your drive or at the kerbside it's more difficult.
2. If you have another good wheel on the car, often the OSR because it tends to get kerbed less, just swop it over with the poor wheel whilst you take the readings. Of course you still need to check it's OK after you've swopped it!
3. Sometimes, because it's usually the very edge of the rim which gets damaged, you can use the bit where the tyre bead seats. That's the bit with the white chalk on it in my picture. But you still need to check it for trueness (is that a word?). I find this is often a good place to use.

Finally. Anyone had experience of the Gunson Trakrite roll over tool? I really like the look of it. In particular the fact that it works by detecting whether any scrub is taking place regardless of what you might "think" you've got your wheels set up at! It probably costs about what one adjustment might cost at a large tyre retailer and it's been around (in a couple of iterations I think) for quite a few years now so maybe actually works?
So, anyone used one or seen one used? Any good?
Regards
Jock

Click to expand...

I was just reflecting that for option 2 above the preferred 1st choice always used to be the spare as it often never saw the light of day and was therefore in pristine condition. Now a days you'll be lucky to find a space saver (grrrrrrr! Detestable devices!) Let alone a full size spare! You may not even have a spare wheel well at all! (More Grrrrrrrring!)

It's a glorious morning and I'm deciding which of my gardening tasks to prioritize as I'm watching the Andrew Marr show and eating my wheatabix. Just had a quick reread of what I've written in this thread and it has occurred to me that those of you from a less technical background may be wondering why, having talked about Camber, King Pin Inclination, etc I chose to only consider Toe settings?

Let's consider what these things are and what their main effects are on how your car behaves. There are four main aspects:- Castor - Camber - K.P.I. (King Pin Inclination) - Toe angles.

Castor is probably the easiest to understand. Think about a pedal cycle. The handlebars are connected to the steering head which is basically a tube, supported in two ball races, going down to the forks which end in the front spindle wheel bearings and wheel. Now stand to the side of the bike and look at this assembly. The head and fork assembly are not vertical are they? The end of the forks where the spindle is mounted is considerably in front of the top of the steering head (where the handlebars connect). Now consider the point of contact of the front tyre with the ground, it too is forward of the top of the steering head. Take a line drawn through the steering head to the point at which the tyre contacts the ground and compare it to an imaginary vertical line, that's your Castor Angle. By the way, that's why you can, if you're clever, ride a bike hands free. To relate this to a simple car set up if you look at a MacPherson strut set up and draw an imaginary vertical line through the bottom arm ball joint, you will find the top mount is slightly behind it. It is this angle which has the greatest effect on self centering.

Camber is simply whether the wheel is vertical to the road surface, leaning in at the top (negative camber) or leaning out (positive camber). You would think having it vertical would be the obvious way to do it but I can't actually think of any vehicle I've ever worked on where the camber angle was zero! The way in which the suspension works and the use to which the vehicle is being put dictates the angle.

King Pin Inclination is maybe a little more difficult to take in as modern vehicles don't have king pins! Let's think about our MacPherson strut again. As far as steering geometry is concerned it has a top mount and a ball joint at the bottom on the suspension arm. As you turn the steering wheel the strut rotates about these two points. If the top mount and ball joint were directly, vertically, in line then the road wheel would have to roll around a small radius as the steering is turned. However if you arrange for the ball joint and top mount to be positioned such that a line drawn from the top mount, through the ball joint, to the ground, were to intersect a point in the middle of the tyre contact patch then the tyre would pivot around this point without having to roll. This reduces the effort needed at the steering wheel. This is called "centre point steering". On the older cars with beam type front axles, king pins and narrow tyres, it was often achieved by giving the wheel quite a lot of positive camber together with a negatively inclined king pin. Try googling for 1920's cars and look carefully at the front wheels. It is really obvious once you know what you're looking at. More modern vehicles, with wider tyres and power steering tend to sacrifice this effect for other advantages in steering "feel" and how the wider tyres grip the road

Toe settings. I hope my original post has given the idea of what that's all about, suffice to say it's about whether the front wheels are splayed out or knock kneed!

Generally speaking any angles measured on one side of the vehicle must be comparable to the ones on the other side if the vehicle is to drive well. The manufacturer will specify the actual values.

So, why did I decide to concentrate on Toe settings? Well, because setting toe is by far the most common of the four to be performed. (And, in my experience, the most likely proceedure to have been previously wrongly performed!) On the majority of vehicles Castor, Camber and K.P.I. are built in to the vehicle when it is assembled, being dictated by the mounting points of the components. So if it is checked and found to be wrong it is likely to be accident (or the like) damage to structure or components and as such is generally likely to be difficult to sort out. Having said that there are a small number of vehicles where some of these angles are adjustable, often by shimming or eccentric mounting bolts, but they are in the minority. Checking and setting toe is quite common requiring to be done after renewing components such as, track rod ends or other ball joints and steering parts, suspension components, to correcting tyre wear, etc. Incorrectly set Toe is far more likely to be the reason for poor tyre wear or "weird" steering effects than the other things discussed above, and a good thing too as it's nearly always the cheaper to sort!

Hope that was useful and hasn't sent too many people to sleep! I'm off out into the garden and sunshine, now where did I put my "gardening" hat?
Regards
Jock