Motorsport Wheel Alignment: Step 1: Setup Suspension Components
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Step 1: Setup Suspension Components
19.49
| 00:00 | - For step 1, the first thing we would normally do is jig any adjustable components. |
| 00:06 | In particular, this means any adjustable suspension arms we might have fitted or have to fit to the car. |
| 00:12 | This is an important step in some cases as we'll be using the wheel hubs as a reference for setting our toe strings later on. |
| 00:18 | Meaning we want the suspension to be set up as symmetric as possible. |
| 00:23 | In this case, because I want to check the current setup of the car that it has now, before moving onto the new setup, I'm going to leave the arms set how they are now. |
| 00:31 | However I'll be rechecking the toe string alignment as I move through the process. |
| 00:36 | Particularly after any arm length changes. |
| 00:39 | If you have adjustable anti roll bar links, we want to disconnect one of these from the front and rear axle respectively. |
| 00:47 | This prevents any load from being built up inside the bar when we're making ride height adjustments later on. |
| 00:53 | We'd come back and adjust these at the end of the alignment when we refit them. |
| 00:57 | In this case we only have adjustable links in the rear so I'll leave the front connected and the rear disconnected. |
| 01:04 | Next we want to set our tyre pressures. |
| 01:06 | This is an important step because if the tyre pressures vary too much, they can make a significant difference to our ride heights and how flat the car sits. |
| 01:14 | We want to set them to their approximate hot running pressure so they are close to how they'll be when they're running on the road or track. |
| 01:21 | For this car, I'm going to use 25 psi. |
| 01:24 | I also suggest having a representative amount of fuel in the car. |
| 01:27 | A good starting point is the average amount of fuel you'll tend to carry around with you. |
| 01:32 | For this car, as it's used for endurance racing, I've used half a tank of fuel. |
| 01:38 | This is simply to make sure that our rear ride height is set with a sensible amount of weight in the rear of the car. |
| 01:44 | In order to complete the wheel alignment accurately, we need the car to be sitting on a level surface. |
| 01:50 | If you're lucky enough to have a sufficiently flat surface to set your car up on already, then you can skip this step. |
| 01:57 | In the course, we left setting our flat patch until step 2. |
| 02:00 | In this example, I'm setting it up in step 1 as I prefer to have the car sitting on a flat surface before going ahead and setting the coilover lengths and ride heights that we'll get onto soon. |
| 02:10 | We just want a surface that's flat enough that it's not going to influence our wheel alignment and ride height measurements. |
| 02:16 | Things like camber in particular can be quite a long way off if your car isn't sitting flat. |
| 02:21 | There are a few different ways you can get the car sitting level. |
| 02:24 | The easiest is to have a flat section of smooth concrete. |
| 02:28 | Unfortunately these are quite rare as almost all garages and driveways have a certain slope built into them to help water drain away and not pool. |
| 02:37 | A low budget option is to use thin flooring tiles to pack up the low corners of the car so that each tyre contact patch is sitting on a flat surface. |
| 02:46 | There are a few ways you can find out how many tiles you need at each corner. |
| 02:50 | But one is to use a flat section of bar and a builder's level. |
| 02:54 | Mark out how far apart each of the tiles needs to be to get them in the right place to fit under each tyre. |
| 03:00 | An easy way to do this is to mark the position of each tyre with the current position before rolling it away. |
| 03:05 | Then use your level and section of flat bar while adjusting the number of tiles at each corner until you have each of them at the same height. |
| 03:13 | It's a good idea to use something to space the level up from the tile surface. |
| 03:17 | In this case I've just used some sockets that are each the same length as each other. |
| 03:21 | Start on the front axle, measuring side to side. |
| 03:24 | Then move to the rear, also side to side. |
| 03:26 | Then you can measure forward and aft between the front and rear axles. |
| 03:30 | As the wheel base will generally be longer than your level, use a section of flat bar to bridge the gap and place the level on this. |
| 03:37 | One tip here is that once you've found the combination of tiles you need, record how many you need for each corner and if possible leave some permanent markings for their position on the ground to speed up this process for next time. |
| 03:48 | Another option is to use a set of adjustable height platforms like these ones here. |
| 03:52 | These are designed specifically for motorsport use. |
| 03:55 | In this case they're supporting a set of corner weighting scales and while we won't be performing corner weighting as part of this wheel alignment setup in this example they still make for a convenient and flat place for each tyre to sit on. |
| 04:07 | While using platforms like this is a more expensive option, it gives us a much higher accuracy than what we can achieve otherwise. |
| 04:14 | Not only can we quickly and easily set the height of these platforms by rotating the corner feet, we can also set each pad to be level individually to ensure the entire surface is flat. |
| 04:25 | Another advantage is by raising the car up on a platform, it makes it easier to work on. |
| 04:30 | In many cases this means we don't need to jack the car up in order to make some of the adjustments. |
| 04:36 | Before we're ready to set up the patch we first need to mark out the position of all 4 tyres of the car. |
| 04:42 | Then roll the car out of the way. |
| 04:44 | This allows us to set up the scales in the right place for each corner. |
| 04:48 | You could just as easily use a builder's level to set up this flat patch. |
| 04:52 | But in this case we'll make use of another tool to show an alternative method. |
| 04:56 | Here we have a laser base patch setup tool. |
| 04:59 | The idea is that we have a laser plane line projected from a unit placed on one of the scales. |
| 05:04 | This unit is self levelling with its own internal gimble. |
| 05:08 | So we know the plane it projects across the workshop is level in both directions. |
| 05:13 | Then we place these calibrated targets on the other 3 corners to help us set the height of each pad. |
| 05:19 | The first step is to set each individual pad to be level. |
| 05:23 | We can do this using a 2D bubble gauge that is built into each target. |
| 05:27 | Once each pad is set level, we can then turn the laser on and start adjusting the heights. |
| 05:32 | From there we just need to adjust each corner of the platforms in equal steps to keep them level and also bring them to the height of the laser line. |
| 05:40 | Once the patch is set, do a final check that each individual pad is still level. |
| 05:46 | Now we can mark the position of each platform on the floor then pull them out of the way and we can roll the car back into place. |
| 05:52 | With the car back in the right spot, jack it up and place the platforms underneath each tyre. |
| 05:58 | One thing to note here is that you need to use something to allow each tyre to slip on the surface which is something we went through in the main body of the course. |
| 06:06 | Each tyre travels through an arc as it moves through its travel. |
| 06:10 | So if we didn't have something for the tyres to slip on, the suspension would not sit in its natural position and the ride height would be higher until the suspension was allowed to settle. |
| 06:20 | Here we're using these BG Racing turn plates on the front and some homemade slip plates on the rear. |
| 06:26 | Both of which you've already seen inside the course. |
| 06:28 | We place these under each tyre before letting the car down. |
| 06:32 | It's important you have a way of locking the brakes on for the duration of the process. |
| 06:36 | This will stop the car rolling off the scales during the alignment which would be potentially damaging and dangerous. |
| 06:42 | Here I'm using a pedal locking rod to hold the brake pedal on. |
| 06:45 | I also recommend leaving the handbrake on and the car in gear as backups. |
| 06:49 | Ideally you should have a way of locking the steering wheel in the straight ahead position. |
| 06:55 | This will prevent the steering wheel from rotating during the alignment and also ensure that the steering wheel will be straight as the car travels down the road. |
| 07:02 | You can possibly make use of the car's factory steering lock to hold the steering straight but in many cases the wheel won't be perfectly straight. |
| 07:10 | You could also use a tool similar to what's shown here. |
| 07:13 | Alternatively you can leave the steering unlocked throughout the process. |
| 07:16 | But you'll have to check the steering wheel is still sitting straight ahead regularly throughout the process if you do this which isn't ideal. |
| 07:24 | Now we're ready to lower the car onto the patch. |
| 07:26 | Ideally you should have either some representative driver ballast or a friend of similar weight that's happy to sit in the car throughout the process. |
| 07:34 | This is helpful to get the car at a ride height that's as realistic as possible to how it would be driven either on the road or the track. |
| 07:41 | In this case, I'm using 90 kg of ballast weights. |
| 07:44 | 80kg in the seat and 10 kg on the floor in front of the seat to approximate the driver in the car. |
| 07:51 | The ballast weight that you use should be equal to the total driver weight with them wearing all of their safety gear. |
| 07:56 | I prefer to use ballast weights rather than having a helper sit in the car as it helps to increase the repeatability of the alignment process by removing another variable. |
| 08:06 | These coilovers were only recently fitted to this car and had only been fitted to get the car rolling so the first thing we needed to do is go ahead and set the ride height and lower mount position for each of them. |
| 08:17 | You know from the course that the purpose of the lower mount is to set the position of each wheel when the suspension is at full compression as well as getting your bump to rebound ratio correct. |
| 08:28 | If your ride height and bump to rebound ratio have already been set you can skip this step. |
| 08:33 | So the first thing we need to do is go ahead and set these lower mounts in the correct position. |
| 08:39 | We need to carry out this process at one front and one rear corner of the car. |
| 08:44 | I'm going to use the front left and the rear left for this. |
| 08:47 | Starting with the left front corner, we remove the coilover and then strip the spring and bump stop. |
| 08:52 | We then reassemble that corner minus the spring and bump stop and refit the wheel. |
| 08:57 | While you're there, if you haven't already, remove one of the anti roll bar links from both the front and the rear anti roll bars so we can move both sides of the suspension through their travel without restriction. |
| 09:08 | In almost all cases, when you're disconnecting an anti roll bar like this, all you need to do is disconnect one of the links. |
| 09:15 | On this Integra however, due to the way it's packaged it's actually easier to remove the whole front anti roll bar to stop the bar interfering with the lower control arm as we move the suspension through its full range of travel. |
| 09:26 | We now go and jack up this corner of the car to check the interference between the tyre and inner guard at full suspension travel. |
| 09:34 | In this case, when the suspension is at full compression, the limiting factor is actually from the upper control arm hitting the chassis. |
| 09:41 | At the point where the upper control arm is coming into contact with the chassis, we still have a significant amount of damper travel remaining before we'll bottom it out. |
| 09:49 | We want the suspension travel to be limited by the damper body. |
| 09:53 | This ensures that when we have a bump stop fitted, we will have a progressive increase in rate without any shock loading which is both dangerous on track and damaging to the car. |
| 10:03 | Looking at the top damper mounts on the chassis, we can see from the witnesses where the paint has chipped, that previously the top control arms have been contacting the chassis for some time. |
| 10:13 | The first thing to try to fix is by extending the damper length. |
| 10:17 | We need to extend the lower mount which will essentially lower the position of the upright and suspension arms, relative to the amount of damper travel. |
| 10:25 | This will help the damper to bottom out before we get contact with the top arm and the chassis. |
| 10:30 | We crack off the lower mount lock nut and wind the damper body to lower the mount. |
| 10:35 | We then go back and recheck a top arm and tyre clearance. |
| 10:39 | In this case, after a few iterations of extending the lower mount positions and checking the clearance, we reach the point where we will not have enough safe thread engagement between the damper and the lower mount if we continue to extend it. |
| 10:52 | The minimum engagement will depend on the materials involved and the suspension type. |
| 10:56 | You should check with your coilover manufacturer if you aren't sure how much is safe for your application. |
| 11:03 | I'm not willing to have less than 20 mm of thread engagement so I've set it to 20 mm and locked up the lower nut. |
| 11:10 | With the suspension fully compresssed, we have around 15 mm of damper travel remaining when the top arm contacts the chassis. |
| 11:18 | We're in a better position than when we started but we can't reduce this gap any more with the lower mount adjuster. |
| 11:24 | At this point, as long as we're stuck with the components that we have, we have no option but to limit the damper travel to prevent the top arm from contacting the chassis at full compression. |
| 11:35 | This means a spacer will need to be machined to reduce the available damper travel. |
| 11:39 | This is not an ideal solution to reduce our available travel but it's the lesser of two evils. |
| 11:44 | The spacer we'll have made will be 20 mm thick to give some safety margin and will be machined from delrin. |
| 11:51 | Delrin is simply an engineered plastic that's suitable for an application like this. |
| 11:55 | The spacer will be 40 mm in diameter with a 15 mm hole. |
| 12:00 | This will allow it to interface properly with the bump stop at full compression. |
| 12:05 | With the spacer in place and now having the lower mount set in a position so we won't have any contact between the top arm and the chassis, we can move onto setting our base ride height. |
| 12:15 | We're going to use the same principles to set our ride height as we did in the course but with a slight variation in the process. |
| 12:21 | In particular, this process will be useful if you aren't given any parameters by the coilover manufacturer and they don't come pre set from the factory at the correct position. |
| 12:30 | We're going to set our ride height based on the 1/3 to 2/3 travel rule where we reserve 1/3 of our suspension travel in droop and the other 2/3 for compression. |
| 12:39 | There are a few different ways we can figure this out but I'll go with what I think is the simplest. |
| 12:44 | I put a piece of tape on the outside of the fender and add a small pen mark on the tape above the centre of the wheel. |
| 12:51 | Now I take a tape measure and with the suspension still at full compression, remembering that the travel is being limited by the new spacer, I measure the distance from a point on the wheel to that pen mark. |
| 13:03 | You can use the centre of the wheel or the wheel lip, whatever is more convenient for you. |
| 13:08 | You just need to use a place that's easily repeatable. |
| 13:12 | In this case I'm using the lower wheel lip which is convenient for this particular wheel design. |
| 13:16 | This is our reference measurement for the suspension being fully compressed. |
| 13:21 | Write this down. |
| 13:23 | In this case I measured 500 mm, now when the suspension moved to full droop, where we can take the same measurement. |
| 13:31 | Here I've got 629 mm so now we have a measurement for the wheel position at full compression and full droop. |
| 13:39 | Subtracting the full compression value from the full droop value gives us 129 mm which is our total travel at this point on the wheel. |
| 13:47 | Dividing our travel by 3 gives us 43 mm. |
| 13:51 | This gives us our value for 1/3 of the available travel. |
| 13:54 | Taking our full droop value, we subtract 1/3 of our travel which gives us 586 mm. |
| 14:02 | This value is the target wheel position for the static ride height we need to have with this car sitting on its wheels. |
| 14:09 | Because of the procedure we've just gone through, when we set the ride height using the spring perch at this wheel position, we know for sure that we have 1/3 of our available travel available in droop and 2/3 available in compression which is exactly what we want. |
| 14:23 | Because we set the lower mount already, we also know that the tyre cannot come into contact with the inner guard so we can be happy it's safe for that too. |
| 14:31 | Now we need to go and repeat this exact process we carried out in the left front on the left rear too. |
| 14:37 | On the rear, rather than the suspension arm limiting our travel, it's the contact between the tyre and the fender. |
| 14:43 | Which is happening at multiple places around the fender. |
| 14:47 | This is also something we need to avoid to prevent tyre damage. |
| 14:51 | After carrying out the same process on the rear, extending the lower mount as far as I was willing to go, with 20 mm of engagement left, we had the same situation but we still had damper travel remaining with the tyre in contact with the fender. |
| 15:05 | The same solution we used in the front is needed in the back with a custom delrin spacer. |
| 15:11 | Coincidentally the exact same spacer dimensions we needed on the front are what's needed in the back with a 20 mm thickness. |
| 15:18 | With the rear end travel and contact issues sorted, we can now move on in the process. |
| 15:23 | Now record the full compression and droop wheel position measurements for the left rear as well as the target ride height using the 1/3 travel rule. |
| 15:33 | Don't forget we need to replicate the lower mount positions that we set on the left side, on the right side of the car too. |
| 15:39 | Take a convenient reference point on the damper for that lower mount, then transfer those to their respective corners of the car, ensuring that the lower mount is set symmetrically. |
| 15:48 | For the front dampers, this was easiest with both front dampers removed. |
| 15:52 | Using a steel ruler and holding it up against the damper body from underneath the reference position for the front left was recorded and then transferred to the front right damper. |
| 16:01 | Making the lower mount position symmetrical. |
| 16:04 | A similar process was carried out for the rear. |
| 16:06 | But because of the different packaging of the rear, the lower mount position could be measured and transferred in place without having to remove the rear dampers. |
| 16:14 | Now we can go ahead and completely reassemble both the front left and the rear left dampers with our springs and bump stops. |
| 16:22 | Now we can put some tape and pen marks on the right hand side of the car too, then record these full droop values. |
| 16:27 | We'll need these as well to set the ride height of the other side of the car. |
| 16:31 | Using the 1/3 suspension travel value we got from the left side, calculate the target ride height wheel position values for the right hand side of the car. |
| 16:40 | Now we have our target ride heights for all 4 corners. |
| 16:43 | Now we can drop the car down and start setting our ride heights. |
| 16:46 | On the rear, we should leave the rear anti roll bar disconnected and we'll adjust this at the end of the process. |
| 16:52 | However with the front not having an adjustable link length, we'll refit this now. |
| 16:56 | In our case, as we completely unbolted the front anti roll bar, we need to remount this too. |
| 17:01 | With the car sitting on its tyres on the flat patch, bounce on the front and the rear 2-3 times, this is to help make sure that the suspension is fully settled and the ride height will be accurate. |
| 17:11 | Even though we have slip plates under the tyres, there will still be some friction involved that we need to overcome. |
| 17:17 | Each time you raise and then drop the car back onto the ground, this same settling process needs to be carried out. |
| 17:23 | Take the ride height measurements at each corner of the car, comparing these measurements to the target values we have, we can now write out how much we need to change the ride height by in each corner. |
| 17:33 | Here we see the actual wheel positions and our target wheel positions next to each other. |
| 17:37 | Using these, we can easily calculate the amount we need to change each one. |
| 17:43 | Now we hack the car up and make our ride height changes by moving the spring perches. |
| 17:47 | This car doesn't have a 1:1 motion ratio between the dampers and the wheel at either end of the car. |
| 17:54 | So in order to speed up our process, it's worth roughly figuring out how much we'll need to move the perch for a given amount of wheel movement. |
| 18:01 | You can estimate this by measuring roughly how far along the control arm the damper is attached. |
| 18:07 | Divide this value by the total control arm length, repeat this for the front and the rear axles. |
| 18:13 | For this car, these ratios come out at roughly 0.7 for the front and 0.77 for the rear. |
| 18:20 | To find out how much we need to move the spring perch for the front left for example, we multiply the change that we need at the wheel, which is roughly 8 mm, by the approximated motion ratio of 0.7. |
| 18:31 | This gives us approximately 5.6 mm we need to lower the spring perch to get to our target ride height. |
| 18:39 | We figure out how much we need to adjust the spring perch at each corner of the car and go ahead and make those adjustments. |
| 18:44 | In this case, all spring perches needed to be wound down, each by the amounts shown here. |
| 18:48 | Note that first you'll need to undo the bolt locking the spring perches. |
| 18:53 | With the wheels back on, we can let the car back down on the patch and settle it again. |
| 18:58 | From here, it's just repeating the measurement, adjustment and settling process until you're at your target ride height. |
| 19:05 | If you follow this procedure we've laid out here, you'll get to it pretty quickly. |
| 19:09 | In this case we were at the target ride height straight away, after the first adjustment. |
| 19:13 | It's worth noting that many coilovers will come with their lower mount position preset from the factory. |
| 19:20 | In most cases, this is going to be correct but to some extent it will depend on the combination of wheel and tyre size you have. |
| 19:27 | In this case, as there's non standard suspension arms fitted causing clearance issues, it was also important to go through this process. |
| 19:34 | So I always recommend checking it at least. |
| 19:37 | Once you're happy with the ride height, retighten the locking bolts on the spring perches. |
| 19:41 | Our ride height is now set and we're ready to move onto step 2. |
