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Practical Corner Weighting: 5. Making Ride Height Changes

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5. Making Ride Height Changes

05.04

00:00 - We're now at a point where we're going to be making some ride height adjustments to our car in order to target our desired cross weight percentage.
00:08 Before we do this, it's important to understand what we're trying to achieve and also the implications of some of the changes we're going to be making.
00:17 When we are dealing with a production based road car, where the driver is offset to one side of the car, in this case a right hand drive car, we need to understand that it's going to be all but impossible to get a perfect 50% cross weight as well as getting an even spread of weight across both our front and our rear axle lines.
00:37 In this case, looking at our starting point we can see we've got a significant discrepancy across the rear axle line in the region of about 50 kg left to right.
00:47 We've also got a slightly lower variation across our front axle line.
00:51 So we need to consider this because as we learned in the body of the course, this can affect our braking performance.
00:58 Here, we're going to start by targeting our 50% cross weight percentage and in our next module, we'll be able to test at the track and see if this is in fact going to give us our desired results.
01:12 Now when we are making our ride height changes as well, we need to consider the implications of those.
01:18 We could for example make one dramatic ride height change at one corner of the car and potentially get us onto our target.
01:25 However this may cause other implications that are undesirable.
01:30 For example it could adversely affect our bump and rebound travel on that particular corner of the car.
01:37 When we are making dramatic ride height changes as well we need to understand that there are some potential effects on our alignment specifications so my personal preference here is to make smaller changes to multiple corners of the car rather than trying to fix this all in one single adjustment.
01:55 Before we make our ride height changes, we'll look again at our existing corner weights and we can see here that in order to get our cross weight percentage to our target of 50%, we've got two options available to us.
02:08 We can either reduce the weight on the left front and right rear or alternatively increase the weight on the right front and left rear.
02:16 For my first change here I'm going to reduce the ride height on the right rear which will have the effect of reducing the weight on the left front and right rear together and this will of course increase our cross weight percentage.
02:31 We'll get our car off the scales and get it up in the air and the wheel off and we'll make a ride height change here of 1.5 turns to this right rear corner.
02:41 Once we've got our change made, we can get the car back on the ground, we can settle the suspension and get the car back onto the scales to see the effect of that one change.
02:51 With the car back on the scales, this time we can see that our cross weight's increased further to 674 kg, our cross weight percentage now 49.6% so we're creeping closer to our target of 50%.
03:04 Still got a little bit of work left to do here.
03:07 We can see that that change in our cross weight percentage has come from an additional 3 kg added into the left rear, smaller change to our right front and of course the respective corners of the car, the weight has been reduced.
03:20 What we're going to do now is roll the car back off and we're going to make a further change of one turn at the left rear of the car.
03:27 So what I'm doing here is splitting the difference in where I'm making our adjustments.
03:33 You'll remember at this stage we've only made a change of 1.5 turns on the right rear, this will be a total of two turns on the left rear.
03:39 So the sort of changes we're making there, the actual ride height change will have little impact on our alignment settings and it's also going to have limited effect on the suspension operation.
03:51 Let's get the car off the scales, we'll make that further change to our left rear, we'll settle the suspension again, load it back up and we can have a look at our results.
04:01 It's worth mentioning here that while we've now hit our target of 50% cross weight, we can see that in particular on the front axle line, we've got a 30kg imbalance between the right front, which is heavy and the left front which is light.
04:15 And as we've already discussed, this could have an impact on our braking performance.
04:20 At the end of the day, this process is always going to be something of a compromise on a road car like this.
04:27 And it's our job, in the next step to test our results on the track and make sure that the 50% cross weight that we've targeted actually does give us an improvement in our handling balance, our performance on track and ultimately our lap times.
04:41 Now that we've got our corner weighting complete, the final task is to lock off our spring perches to make sure they don't move.