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Motorsport Wheel Alignment: Measuring & Adjusting Toe

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Measuring & Adjusting Toe

07.22

00:00 - Once we've got our string alignment equipment set up, we can now easily make measurements of our toe on the front and rear of the car and then make adjustments to get our toe wherever we've decided that we want it to be.
00:11 In order to measure our toe, this is relatively straightforward, we're simply going to take our steel ruler and we're going to measure between the front edge of the rim and our sting line and then we're also going to measure between the rear edge of the rim and our string line.
00:26 We want to make sure that we're making this measurement or taking these points horizontally through the centreline of the wheel.
00:32 When we're making these measurements, we also want to take care that we don't introduce any parallax error.
00:38 Once we've got these two measurements, we're simply going to subtract one from the other, the difference is going to give us our toe at that particular corner of the car.
00:47 And when we're looking at these numbers, we need to understand that if our measurement on our ruler is larger at the front of the rim compared to the rear, this means that we've got toe in.
00:56 On the other hand, if the measurement at the rear of the wheel is larger than at the front, this means that we have toe out.
01:03 Before we take any toe readings, it's also important to make sure that we've centralised the steering wheel so that it's pointing directly straight ahead.
01:11 If we fail to do this and we take our toe readings at the front end of the car, they'll end up being offset which can be misleading.
01:18 Worse still, if we leave the steering wheel offset while we are making toe adjustments, we're going to end up with our toe correct, but now when the car is tracking in a sraight line, our steering wheel will be offset to one side of central.
01:32 Before we make any changes, it's also important to understand where we need to make our changes and the implications of these changes.
01:40 For example, at the front end of the car, we're going to be making our toe adjustments by adjusting the outer tie rod on our steering rack.
01:47 Now we also need to understand that depending where the steering rack is placed, will affect the type of change we need to make.
01:54 For example, with our Toyota 86 development car, the steering rack is placed rearward of the centreline of the hub.
02:01 This means that if we extend our tie rod outwards, this is going to result in toe in.
02:07 On the other hand, if the steering rack was placed in front of the centreline of the hub, by extending the steering rack outwards or the tie rod outwards, we're actually going to result in toe out.
02:17 So it's important to make sure we understand what direction we need to make our change in order to achieve a specific toe setting.
02:25 At the rear of the car in our Toyota 86, we've got a multi-link suspension system which is relatively common on late model cars.
02:33 Here we're looking for a toe control arm.
02:36 And we can see that this is placed in front of the centreline of the hub.
02:40 Here, because this is placed in front of centreline of the hub, extending the toe control arm will result in toe out, shortening it, on the other hand will result in toe in.
02:50 Depending on the specific suspension setup, we may also find that by adjusting toe we also affect our camber or vice versa.
02:59 So when we are making these changes, we also want to make sure that our camber is stating where we've set it.
03:05 Sometimes this can be an iterative process.
03:09 For our example here, we're going to look at adjusting the toe on the front right corner of our Toyota 86.
03:15 We want to start by taking a measurement so we know what our existing toe is.
03:20 By placing the rule against the front edge of our rim and reading against the string line, we've got a measurement of 38 millimetres.
03:28 If we do the same at the rear of the rim, we can see that our measurement is now 41 millimetres.
03:33 So subtracting 41 from 38, gives us a toe reading of three millimetres at the front right corner of the car.
03:41 Because the reading at the rear edge of the rim is larger than at the front, this means that we have three millimetres of toe out.
03:48 In this case, three millimetres of toe out is a little bit aggressive and what we actually want to target here is one millimetre of toe out per side.
03:56 So what we need to do here is remove two millimetres of toe from this particular corner of the car.
04:01 Now we know that in order to do that, because we have too much toe out, what we're going to need to do is extend our tie rod and that will result in us toeing in the front right hand corner of the car.
04:13 Before we can make our change, we're going to need to loosen off the locking nut for our tie rod end.
04:19 Now this is easiest done on a hoist and we can do this before we start making our alignment setup.
04:26 However if you want to know what your existing toe is, you need to make sure that when you're loosening that locking nut, you don't accidentally or inadvertently adjust the tie rod length.
04:35 Once we've got that locking nut loosened off, we can start making our adjustments, extending the tie rod out until we've got our target of one millimetre of toe out.
04:45 When we are making these adjustments, we also need to be mindful of ensuring that we still have enough thread engaged in our tie rod end and the rule of thumb we're using here is that we want at least 1.5 times the diameter of our screw thread engaged in our tie rod end.
05:00 Making our adjustments here can be an iterative process and we do need to also be mindful that the steering doesn't move, making sure that our steering wheel is still pointed straight ahead.
05:11 This is a little bit easier to achieve if we've got our car set up on slip plates while we're making our toe adjustments.
05:18 With our toe now adjusted we can see that the measurement on the front edge of rim is 39 millimetres and our measurement at the rear of the rim is 40 millimetres.
05:27 Again, if we subtract 40 from 39, we've got one millimetre of toe out on the front right corner, this is exactly what we're targeting.
05:35 Once we're happy with our toe, we can then go back, double check our camber, we'd also make sure that our steering wheel hasn't moved and provided we're happy with everything at this point, we can tighten up that locking nut again.
05:49 Now of course, this locking nut is absolutely critical to the safety of our car.
05:53 So we want to be very certain that we have adequately tightened it.
05:58 Once we have tightened that locking nut, it's always a good idea to perform one final check, just to make sure that our toe hasn't moved, or we haven't inadvertently adjusted the tie rod end as we've been tightening that locking nut.
06:10 So we've not looked at making the toe adjustment at the front end of the car, the process to go through at the rear end of the car is essentially identical.
06:19 It can be beneficial when we are making our toe adjustments, if we can do this without needing to jack the car off the ground.
06:27 This aids repeatability and consistency with our measurements because we don't need to setting the suspension again when we drop it back off the jack.
06:35 This can be a little bit tricky, particularly on lowered cars but even in the case of our Toyota 86, we can get access to both the front and rear toe adjusters without needing to jack the car off the ground.
06:47 If on the other hand you're dealing with a car where you've got no option but to jack the car off the ground, in order to access the toe adjusters, it's important to make sure that when you lower the car back on the ground that you do allow the suspension to settle properly.
07:01 This can be achieved by rolling the car backwards and forwards a few metres as well as applying some load and bouncing up and down separately on the front and the rear of the car.