Motorsport Wheel Alignment: Step 1: Setup Suspension Components
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Step 1: Setup Suspension Components
15.39
| 00:00 | - For step 1, the first thing we need to do is jig any adjustable components. |
| 00:04 | In particular, this means any adjustable suspension arms we might have fitted or have to fit to the car. |
| 00:11 | This is an important step in some cases as we'll be using the wheel hubs as the reference for setting our toe strings later on. |
| 00:18 | Meaning we want the suspension to be symmetric as is practical. |
| 00:22 | The car has all factory suspension arms so we don't need to worry about this step. |
| 00:27 | If we have adjustable anti roll bar links, we want to disconnect one side of these from the front and rear axle respectively. |
| 00:35 | This prevents any load from being built up inside the bar when we're making ride height adjustments later on. |
| 00:41 | We'd come back and adjust these at the end of the alignment when we refit them. |
| 00:44 | In this case we don't have adjustable links so we'll just leave these connected. |
| 00:49 | Next we want to set our tyre pressures. |
| 00:51 | 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. |
| 00:59 | 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 the track. |
| 01:07 | For this car, I'm going to use 28 psi. |
| 01:10 | I also suggest having a representative amount of fuel in the car. |
| 01:13 | A good starting point is the average amount of fuel you'll carry around with you. |
| 01:17 | For this car, I've used 1/3 of a full tank. |
| 01:21 | 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. |
| 01:27 | In order to complete the wheel alignment accurately, we need the car to be sitting on a level surface. |
| 01:32 | If you're lucky enough to have a sufficiently flat surface to set your car up on already then you can skip this step. |
| 01:38 | In the course, we left setting the flat patch until step 2. |
| 01:41 | In this example, I'm setting it up in step one as I prefer to have the car sitting on a flat surface before going ahead and setting the coilover lengths and the ride heights that we're going to get onto soon. |
| 01:52 | We just want a surface that's flat enough that it's not going to influence our wheel alignment and ride height mesurements. |
| 01:58 | Things like camber in particular can be quite a long way off if your car isn't sitting flat. |
| 02:02 | There are a few different ways you can get the car sitting level. |
| 02:07 | The easiest is to have a flat section of smooth concrete. |
| 02:11 | 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. |
| 02:19 | 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. |
| 02:28 | There are a few ways you can find out how many tiles you need at each corner but one is to use a flat section of bar and a builder's level. |
| 02:35 | Mark out how far apart each of the tiles needs to be to get them in the right place to fit under each tyre. |
| 02:42 | An easy way to do this is to mark the position of each wheel with the car in position before rolling it away. |
| 02:48 | Then, use your level and a section of flat bar while adjusting the number of tiles at each corner until you have each of them at the same height. |
| 02:56 | It's a good idea to use something to space up the level from the tile surface. |
| 03:00 | In this case I've just used some sockets that are each the same length as each other. |
| 03:04 | Start on the front axle, measuring side to side then move to the rear, also measuring side to side. |
| 03:10 | Then you can measure forward and aft between the front and the rear axles. |
| 03:14 | As the wheel base is generally longer than your level, use a section of flat bar to bridge the gap and place the level on this. |
| 03:21 | 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. |
| 03:33 | Another option is to use a set of adjustable height platforms like these ones here. |
| 03:37 | These are designed specifically for motorsport use. |
| 03:41 | In this case, they're supporting a set of corner weighting scales and while we won't be performing a corner weighting as part of the wheel alignment setup in this example, they still make for a convenient and flat place for each tyre to sit on. |
| 03:54 | While using platforms like this is a more expensive option, it gives us a much higher accuracy than we could otherwise achieve. |
| 04:01 | Not only can we quickly and easily set the height of each 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. |
| 04:12 | Another advantage is that by raising the car up on a platform, it makes it easier to work on. |
| 04:17 | In many cases, this means we don't need to jack the car up in order to make some of the adjustments. |
| 04:24 | Before we're ready to set up the patch, we first need to mark the position of all 4 tyres of the car and then roll the car out of the way. |
| 04:31 | This allows us to set up the scales in the right place for each corner of the car. |
| 04:35 | You could just as easily use the builder's level to set up this flat patch but in this case we'll make use of another tool to show you an alternative method. |
| 04:43 | Here we have a laser based patch setup tool. |
| 04:46 | The idea is that we have a laser plane line projected from a unit placed on one of the scales. |
| 04:51 | This unit is self levelling with its own internal gimble so we know the plane it projects across the workshop is level in both directions. |
| 05:00 | Then we place these calibrated targets on the other three corners to help us set up the height of each pad. |
| 05:07 | The first step is to set each individual pad to be level. |
| 05:10 | We can do this by using the 2D bubble gauge that is built into each target. |
| 05:15 | Once each pad is set level, we can turn on the laser and start adjusting the heights. |
| 05:20 | 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. |
| 05:28 | Once the patch is set, do a final check that each individual pad is still level. |
| 05:34 | Now we can mark the position of each platform on the floor and pull them out of the way so we can roll the car back into place. |
| 05:41 | With the car back in the right spot, jack it up and place the platforms underneath each tyre. |
| 05:47 | 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. |
| 05:54 | Each tyre travels through an arc as it moves through its travel 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. |
| 06:07 | Here we're using these BG Racing turn plates at the front and some homemade slip plates on the rear. |
| 06:13 | Both of these, which you've already seen within the course. |
| 06:17 | We place these under each of the tyres before letting the car down. |
| 06:21 | It's important that you have a way of locking the brakes for the duration of the process. |
| 06:25 | This will stop the car rolling off the scales during the alignment which could be potentially damaging and dangerous. |
| 06:31 | Here I'm using a brake pedal locking rod to hold the brake pedal on. |
| 06:35 | I also recommend leaving the handbrake on and the car in gear as backups. |
| 06:40 | Ideally you should have a way of locking the steering wheel in a straight ahead position. |
| 06:45 | 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. |
| 06:53 | 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 held perfectly straight. |
| 07:02 | You could also use a similar tool to what is shown here. |
| 07:05 | Alternatively you can leave the steering unlocked throughout the process but you'll have to recheck the steering wheel is still sitting straight regularly throughout the process if you do this which isn't ideal. |
| 07:17 | These coilovers were only recently fitted to this car and have not been set up properly. |
| 07:21 | So the first thing we need to do is go ahead and set the ride height and lower mount position for each of them. |
| 07:28 | You know from the course that the purpose of the lower mount is to set the position of each wheel with the suspension at full compression as well as getting the bump to rebound ratio correct. |
| 07:38 | So the first thing we need to do is go ahead and set these lower mounts in the correct position. |
| 07:43 | We need to carry out this process at one front and one rear corner of the car. |
| 07:48 | I'm going to use the front left and the rear left corners for this. |
| 07:51 | Starting with the front left corner, we remove the coilover and strip the spring and bump stop. |
| 07:56 | We then reassemble that corner of the car minus the spring and bump stop and refit the wheel. |
| 08:02 | While you're there, if you haven't already, remove one of the anti roll bar links from both the front and rear anti roll bars so we can move both sides of the suspension through their travel without restriction. |
| 08:13 | 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. |
| 08:20 | On this RX7 however, due to the way it's packaged, it's actually easier to remove the whole front anti roll bar. |
| 08:27 | We now go and jack up this corner of the car to check for interference between the tyre and the inner guard at full suspension travel. |
| 08:34 | In this case, with the suspension at its fully compressed position, the tyre is hitting the inner guard which we could easily tell as this tyre won't easily rotate. |
| 08:45 | To fix this, we need to extend the lower mount so the tyre is not in contact with the inner guard when we're at full compression. |
| 08:52 | We crack off the lock nut and wind the damper body to lower the mount. |
| 08:56 | We then go back and recheck our tyre clearance and keep repeating this process until you have no clearance issues. |
| 09:03 | At this point you can go ahead and relock that lock nut on the lower mount. |
| 09:07 | The next thing we need to do is set our base ride height. |
| 09:09 | We're going to be using the same principles to set our ride height as we did within the course but with a slight variation in the process. |
| 09:17 | In particular this will be useful to you if you aren't given any parameters by the coilover manufacturer and they don't come set at the correct position from factory. |
| 09:26 | 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. |
| 09:37 | There are a few different ways we can figure this out but I'll go with what I think is the simplest. |
| 09:42 | 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. |
| 09:49 | Now I take a tape measure and with the suspension still at its fully compressed position. |
| 09:54 | I measure the distance from a point on the wheel to that pen mark. |
| 09:57 | You can use the centre of the wheel or the wheel lip, whatever is more convenient for you. |
| 10:03 | It just needs to be a place that's easily repeatable. |
| 10:06 | In this case I'm using the lower wheel lip which is convenient for this particular wheel design. |
| 10:11 | This is our reference measurement for the suspension being fully compressed. |
| 10:16 | Write this down. |
| 10:17 | In this case I've measured 502 mm. |
| 10:20 | Now we let the suspension move to full droop. |
| 10:23 | Then we take that same measurement. |
| 10:25 | Here, I've got 654 mm. |
| 10:27 | So now we have a measurement for the wheel position at full compression and full droop. |
| 10:32 | Subtracting the full compression value from the full droop value gives us 152 mm which is our entire total travel at this point on the wheel. |
| 10:42 | Dividing our travel by 3, this gives us 51 mm. |
| 10:46 | This gives us our value for 1/3 of our available travel. |
| 10:50 | Taking our full droop value we subtract 1/3 of our travel which gives us 603 mm. |
| 10:56 | This value is the target wheel position for the static ride height we need to have with the car sitting on its wheels. |
| 11:03 | Because of the procedure we've just gone through, where we set the ride height using the spring perch in 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 what we want. |
| 11:16 | Because we set the lower mount already, we already know that the tyre cannot come into contact with the inner guard so we can be happy it's safe too. |
| 11:25 | Now we need to go and repeat this exact process we carried out on the front left on the left rear too. |
| 11:31 | With this complete, and once we have the reference ride height position for the rear axle, we can go and completely reassemble both of our dampers with our springs and bump stops. |
| 11:42 | Don't forget we need to replicate the lower mount positions that we set on the left side to the right side of the car too. |
| 11:48 | Take a convenient reference point on the damper for that lower mount then transfer those to their respective corners of the car. |
| 11:55 | Ensuring the lower mount is set symmetrically. |
| 11:58 | At this point it's worth mentioning that you do need to be careful with the amount of thread engagement on the lower mount of the coilover. |
| 12:06 | If you extend the damper body too far out of its lower mount it may not be strong enough. |
| 12:10 | The minimum engagement will depend on the materials involved and the suspension type. |
| 12:15 | Check with your coilover manufacturer if you aren't sure how much is safe for your application. |
| 12:22 | While you're at it, put some tape and pen marks on the right hand side of the car too. |
| 12:26 | Then record these direct values. |
| 12:29 | We'll need these as well to set the ride height of the other side of the car. |
| 12:33 | Using the 1/3 suspension travel value we got from the left side, calculate the wheel position values for the right hand side of the car too. |
| 12:41 | Now we have the target ride heights for all 4 corners. |
| 12:45 | Now we can drop the car down and start setting our ride heights. |
| 12:48 | If you don't have adjustable anti roll bar links which is the case on this car, then reattach the disconnected links now. |
| 12:55 | If you do have adjustable links leave them disconnected until the end of the wheel alignment. |
| 13:01 | In our case, as we completely removed the front anti roll bar we need to refit this too. |
| 13:05 | WIth the car sitting on its tyres on the flat patch, bounce on the front and the rear 2 to 3 times. |
| 13:12 | This helps to make sure that the suspension is fully settled and the ride height will be accurate. |
| 13:16 | Even though we have slip plates under the tyres, there is still some friction that needs to be overcome. |
| 13:23 | Each time you raise and drop the car back onto the ground, this same process needs to be carried out. |
| 13:28 | Take the ride height measurements at each corner of the car, comparing these measurements to the target values we have. |
| 13:34 | We can now write out how much we need to change the ride height for each corner. |
| 13:38 | Here we see the actual wheel positions and our target wheel positions next to each other. |
| 13:43 | Using these, we can easily calculate the amount we need to change one. |
| 13:48 | Now we jack the car up and make our ride height changes by moving the springs and perch heights. |
| 13:53 | This car doesn't have a 1:1 motion ratio between the dampers and the wheel at either end of the car. |
| 13:59 | 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. |
| 14:07 | You can estimate this by measuring roughly how far along the lower control arm the damper is attached. |
| 14:14 | Divide this value by the total control arm length. |
| 14:16 | Repeat this for the front and the rear axles. |
| 14:19 | For this car, these ratios come out at roughly 0.67 for the front and 0.77 for the rear. |
| 14:26 | To find out how much we need to move the spring perch for the front left for example, we multiply the change we need at the wheel by the approximated motion ratio. |
| 14:36 | This gives us approximately 2.7 mm that we need to lower the spring perch. |
| 14:40 | We figure out what we need at each corner of the car and go ahead and make the adjustments at the spring perches. |
| 14:48 | Note that first you'll need to slacken off the lock nuts of the spring perches. |
| 14:51 | With the wheels back on we can let the car back down onto the patch and settle it again. |
| 14:56 | From here it's just repeating the measurement, adjusting and settling process until you're at your target ride height. |
| 15:03 | If you follow the procedure we've laid out here, you'll get to this pretty quickly. |
| 15:06 | In this case, we were very close with the first measurement with only one more pass required. |
| 15:12 | It's worth noting that many coilovers will come with the lower mount position preset from the factory. |
| 15:18 | In most cases, this is going to be correct but to some extent it will depend on your combination of wheel and tyre size that you have so I always recommend checking it. |
| 15:28 | Once you're happy with the ride height, retighten the lock nuts in the spring perches. |
| 15:31 | Our ride height is now set and we're ready to move onto step 2. |
