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Motorsport Wheel Alignment: Setting Up a String Alignment System

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Setting Up a String Alignment System

09.57

00:00 - When it comes to making adjustments to our front and rear toe, either at the racetrack or in our home workshop, a string wheel alignment system is essential.
00:10 Now like any tool, using a string wheel alignment system does require some basic knowledge of how to correctly set it up, otherwise we can very easily end up getting readings or measurements off the strings that are complete garbage.
00:24 Essentially the key element in setting up our string wheel alignment system is to make sure that the strings down either side of the car are parallel to each other, as well as parallel to the centreline of the car.
00:36 In this module, we'll be looking at two different styles of string alignment system.
00:41 We'll start with a professional string system, in this case we'll be using the Watkins Smart String system.
00:47 But then we'll also look at a much cheaper option that you can make up from easily and cheaply available parts in your home workshop.
00:54 One of the advantages of using a professional string alignment system is that it will come with two frames that you can attach to the front and rear of the car.
01:02 These frames break down so that they're easy to transport to and from the racetrack and they're also very easy to adjust for different styles of car and this allows you to very accurately locate the bars front and rear at the correct height and in the correct position to make your alignment.
01:18 The bars themselves are the important part here and with a professional string alignment system, these bars will come with a number of machined grooves on them.
01:27 Now this allows you to very easily select a pair of grooves front and rear that will match the track width of your car.
01:34 What we're trying to do here is locate the strings so that they're relatively close to the outside edge of the rim.
01:41 The important part here when we're using these string alignment systems is to make sure that our strings are fitted on the same grooves front and rear of the car.
01:50 This ensures that the strings will be parallel from side to side because the grooves on the front and rear bars are machined accurately at exactly the same distances apart.
02:00 We're going to start by attaching our frames to the front and rear of the car.
02:03 It's easiest to do this by popping the bonnet as well as the boot lid and this will give you access to a variety of areas that you can locate the frames on.
02:12 We want to make sure that the frames are positively located so there's no chance that they're going to slip.
02:17 Although there's not a lot of load being placed on these frames once we're actually performing our alignment.
02:22 We also want to adjust our frames roughly at this point so that the supports for the front and rear bars are approximately at the centre height of our rim.
02:30 This doesn't need to be too accurate because we can go through and make fine adjustments to this later on.
02:36 Once our frames are attached to the car, we can go ahead and mount our bars front and rear.
02:42 Now in the case of our Watkins Smart String system, these bars actually screw together, this makes it much easier to transport as we can break them in half.
02:49 It's important to make sure that the bars are completely screwed together because if they aren't, this will affect the overall width between the grooves on the front bar versus the rear and this will affect the accuracy of our alignment.
03:02 With our bars screwed together, we can now install them at the front and rear of the car.
03:08 I like to initially start by just choosing a reference point on the front and the rear of the car, and I'm going to begin by locating the split in the bar where they come apart, approximately on that central point.
03:19 This is just going to mean that we're going to be at least close to the centreline of the car before we start making any measurements.
03:26 Once we've got our bars located front and rear, it's time to fit the strings.
03:30 And what we want to do here is choose the same slot on the front bar as the rear bar to ensure that the strings remain parallel.
03:37 We're going to choose a slot that's going to locate our strings somewhere in the region of 20 to 50 millimetres off the rim.
03:44 This will make it nice and easy for us to make our measurements accurately from the rim out to our string.
03:50 Once we've got our strings attached, we're going to make sure that they have a small amount of tension on them, to make sure that they're going to be nice and tight, aiding the accuracy of our measurements.
04:00 At this point, it's also a good time to go through and make a find adjustment to our height for our bars front and rear.
04:07 What we're trying to do here is make sure that our strings are running through the centre of our rims.
04:13 Now we get into the tricky part where we're going to need to square our strings.
04:17 Now in the perfect world, what we would do here is measure off a reference point on the chassis front and rear on the left and the right hand side of the car and use this to measure out to our strings.
04:29 What we're trying to do here is equalise the measurements at the front, between the left and right and then again at the rear between the left and right.
04:37 Now on a purpose built racecar this might be quite straightforward and there will usually be a chassis reference point that we can measure to.
04:45 However in the majority of production road cars, this is going to be difficult if not impossible.
04:51 So what we're going to do instead is measure between a point on the hub, on the left hand side and the right hand side of the car out to our strings and we're going to use this as our reference point.
05:02 In order to do this, it's going to be important to make sure that you've removed the centre caps of your wheels, we're not going to be measuring from the wheel itself, but rather from a point on the hub of the car.
05:14 This is an iterative process and it can be quite frustrating to get it absolutely right but it is important to take your time and make sure that all of these measurements are accurate.
05:25 Before we actually take any measurements, it's also important to make sure that our steering is central.
05:31 This is going to make sure that our toe on the front left and front right wheels is approximately equal, meaning that we're not building in any error into our measurements.
05:41 We're now going to start by choosing a corner of the car, in this case the front right.
05:45 We're going to choose a reference point on the hub that we can easily reach with our ruler and we're going to measure out to our string.
05:52 Now for our first round of adjustments we don't need to get too critical.
05:56 There's undoubtedly going to be a range of adjustments front and rear that need to be made so we don't need to be pinpoint accurate here.
06:03 Of course when we are making our measurements, we do need to take into account aspects such as parallax error which we've already discussed in another module.
06:11 Once we've got our measurement for our front right, we're then going to measure exactly the same point on the front left hub and compare the two.
06:18 What we're trying to do here is equalise the two measurements, so what we can do is move the bar across the chassis until they're approximately equal.
06:27 For example, if on the front right hand side we'd measured 35 millimetres and on the front left we've measured 30 millimetres, what we know is that to equalise that, we're going to need to move the bar across until the measurement on both sides is 32.5 millimetres.
06:44 This would have us central with the centreline of the car.
06:47 Once we've made our first adjustments at the front of the car, we can move to the rear and complete the same process.
06:53 Once we've made our first round of adjustments, we're simply going to continue working our way around the car until our measurements are absolutely accurate front and rear.
07:02 It is important to understand here that we aren't looking for exactly the same measurement on every corner of the car.
07:08 Most cars will have a different track width front and rear so this means that the measurements we'll see at the front of the car are seldom going to match what we'll see at the rear.
07:18 The important thing is to make sure that for example the measurements on either side of the front axle line match each other and likewise the measurements on the rear axle line match each other.
07:28 Once our measurements are perfectly matched front and rear, our string alignment equipment is correctly set up and we can actually begin with our wheel alignment which we'll cover in a separate module.
07:38 While a professional string alignment system is very convenient and it's undoubtedly going to save you time, it also does come at a cost and we know that this is out of the reach of many enthusiasts.
07:50 Fortunately we can apply exactly the same technology used in the professional string alignment system in a much cheaper way.
07:57 What we're going to do here is simply use four jack stands and we're going to use two pieces of aluminium extrusion.
08:05 This can be bought very cheaply.
08:07 What we want to do is make sure that those extrusions are a little bit wider than the track width of the car.
08:13 What we're going to do with our aluminium extrusion is to cut some slots on each end and we're going to use these slots to locate our strings, essentially identical to how we use the slots on our professional wheel alignment equipment.
08:26 The important part when we are cutting these slots onto our aluminium extrusion is to make sure that the slots are exactly the same width on the front bar to the rear bar.
08:35 We also need to make sure that these slots will locate our string around about 20 to 50 millimetres off the rim so that it's going to be easy for us to take our measurements.
08:46 Physically cutting these slots onto our aluminium extrusion can be achieved either with a hacksaw or an angle grinder.
08:53 We don't really need deep slots here, just a positive place to locate the strings.
08:58 With our aluminium extrusion slotted, we're now going to place four axle stands around the car and we're going to use these axle stands to support our aluminium extrusions.
09:08 Remembering here that what we want to do is locate that aluminium extrusion as close to the centreline of the wheel as we possibly can.
09:15 Once we've got our aluminium extrusions located front and rear, we can run our strings between the slots that we've just cut.
09:22 That string can be as simple as a piece of nylon fishing wire and we just want to apply a small amount of tension so that the strings are tight.
09:29 From this point, the process is exactly the same as what we've already looked at with our professional string alignment system, we're just going to go through the process of squaring the strings from side to side and front to rear.