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Practical Corner Weighting: 5. Making Ride Height Adjustments

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5. Making Ride Height Adjustments

05.57

00:00 - At this point, we've done what we can do with ballast as well as physically moving weight around inside the car.
00:05 So it's time to optimise our corner weights as far as possible by adjusting the individual ride height at each corner of the car.
00:13 Remember that what we're aiming for in order to achieve equal handling characteristics in left and right hand corners, is typically a 50% cross weight percentage.
00:23 It's worth however considering what range we'd be happy with as you can waste a lot of time beating yourself up trying to get a perfect 50% which isn't essential and isn't realistic and I'm going to be pretty happy with the cross weight if I'm within plus or minus 0.1% of my target.
00:41 Obviously we need to understand what a specific change in ride height will do for our cross weights so we know where to make our adjustments.
00:48 The basic principle to keep in mind is that raising the ride height at one corner of the car will increase the weight on that particular corner as well as the diagonally opposite corner.
00:59 Correspondingly, we'll see the weight on the other two corners of the car decrease.
01:04 In this way, it's important to understand that we aren't making changes in isolation and every change will affect the other three corner weights to some degree.
01:13 So with this in mind, you'll find that if your cross weight percentage is less than 50%, then we could fix this by raising the front right or the left rear corner or alternatively we could lower the left front and right rear corners.
01:27 Conversely if the cross weight is greater than 50%, we would do the opposite, lowering the front right or left rear or raising the left front and right rear corners.
01:37 In this way, we can fix a low cross weight by making adjustments up or down to any corner of the car which begs the question, where do we get started? The reality is that as we adjust our corner weights, we'll make one adjustment at a time and work iteratively towards our target.
01:53 Since we can make the desired changes by raising or lowering different corners of the car, we also need to consider how the changes will affect the performance of the suspension overall.
02:04 What I mean here is that while it might be possible to fix all of your imbalance by adjusting a single corner of the car, this is going to require a more dramatic change in ride height at that corner compared to changing the diagonally opposite corner at the same time or even all four corners simultaneously.
02:22 Assuming we already have our ride height set at a suitable or optimal ride height for our suspension to maintain good control of the car, as well as providing sufficient bump and rebound travel, I suggest starting by making your changes around the car.
02:36 This will mean that each corner may only need an adjustment of one to two millimetres which will have little effect on the suspension operation while still getting your cross weight where you want it.
02:47 In order to make your changes you'll need to jack the car and remove the wheel to gain access to the suspension.
02:52 During the corner weighting process it's a good idea to start by loosening all of the locking collars for the spring perches so that you can make your adjustments quickly and easily, remembering that this will be an iterative process requiring potentially two to three attempts to get your cross weight correct.
03:10 We've already discussed the various ways of measuring ride height and for the purposes of corner weighting, I prefer to measure the height of the spring platforms relative to a reference point on the strut body so that I can be very accurate with my changes.
03:23 Keep in mind though that a motion ratio will mean that a two millimetre change of the spring perch, doesn't necessarily result in a two millimetre change to the ride height.
03:34 The magnitude of change that you'll need to make will be totally dependent on the specific suspension design, the car and how far out your cross weight is.
03:43 I'd recommend starting with a small adjustment of about two millimetres so that you can assess how much this affects your cross weight.
03:50 You can then use this as a guide with further adjustments.
03:54 Once you've made an adjustment you'll need to drop the car back onto the ground and settle the suspension so that you're getting consistent results and the measured corner weights aren't being affected by binding of the tyres and the suspension components.
04:07 As we've discussed within the course, this can be achieved by rolling the car forwards and backwards a few metres as well as bouncing up and down on the strut towers to allow the suspension to overcome any stiction.
04:19 A good sanity check to make sure the car has settled correctly is to track the ride height at each corner of the car after each adjustment.
04:27 As mentioned in the body of the course, the method I'd suggest for this purpose is to measure between the hub centreline and the guard or fender lip at each corner if possible.
04:37 The specific number we're measuring isn't that important but rather we just want a repeatable place to make our measurements.
04:43 If we lower the car back onto the ground and check our measurements, you're likely to find that the ride height may measure as much as 10 millimetres higher than what you previously measured due to the suspension binding.
04:54 After properly settling the car we should find that he ride height at the corners we haven't adjusted is identical to our original measurements.
05:02 This process is iterative and requires a little patience to get it right but once you've become familiar with the specific car, you'll start to get a feel for what magnitude change you'll need in order to make a correction to a specific amount of imbalance.
05:17 It's critical that once we've got our corner weights optimised, that we do remember to lock up all of the spring perches to ensure that the ride height stays where we've set it.
05:25 This is also the time to reconnect our anti roll bars, adjusting the end links to ensure that there's no pre load being applied at the new ride height.
05:33 With everything tightened for a final time it's always advisable to perform one last check of your corner weights just to make sure that nothing has moved around.
05:42 We also want to check our alignment settings as changes to ride height can have a minor effect on camber and toe settings.