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Suspension Tuning & Optimization: Initial Setup and RH Procedures

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Initial Setup and RH Procedures

13.01

00:00 - Properly setting up your coilovers is an important first step in your suspension setup.
00:04 It's one of the first things you should do when you receive your new coilovers and certainly before you start doing any wheel alignment or other setup procedures.
00:13 In this module, we'll look at a practical example for choosing and setting a sensible, practical initial ride height.
00:21 The type of car you're setting up will determine how you make your decisions on your target ride heights.
00:26 As we've touched on a few times within this course, a car with significant aerodynamics with a powerful under floor will become very ride height sensitive.
00:35 For a car like this, we'd be making a lot of our ride height decisions based on a target ride heights for our underfloor.
00:41 In this case, you're likely going to end up biasing a lot of your setup towards aerodynamic forces which will generally compromise your mechanical grip.
00:50 In a car that makes most of its grip mechanically, we'd instead make our ride height decisions based more on the mechanical components we have, the space and room we have for each of them and our available damper travel.
01:02 In this example, we're going to concentrate on our suggested initial ride height set up procedure for a mechanically biased car which is what we believe will be most relevant to people taking this course.
01:14 With this method, the maximum available wheel travel without the tyre coming into contact with anything at full compression is one of the governing factors.
01:22 The other is that when the car is sitting at static ride height, we want each of the dampers to be approximately 1/3 of their maximum available travel.
01:31 This is consistent with what we discussed earlier in the course where we want to reserve approximately 1/3 of our suspension travel in droop and 2/3 in bump.
01:40 This ensures we have sufficient suspension travel for each corner of the car.
01:44 These factors will be the basis of how we set our initial ride height.
01:48 We're going to carry out this process on a Toyota GT86 but it's important to realise that these concepts and methods are generally applicable to any car so let's get started.
01:57 In this module we're going to be talking all about how to adjust your ride height correctly when you get a new set of coilovers.
02:05 Now the reason this is so important is because most modern coilovers have a couple of different adjustments on them and it's really important to understand which one's which and what the purpose is.
02:14 Now I've got an example of a typical aftermarket or motorsport style coilover here, we've got the lower mount which in this case is for a MacPherson strut.
02:23 We've got a fully threaded damper body here, we've got a couple of different lock nuts, there's this nut here locks the damper body to the lower mount itself and this nut here adjusts the position of the spring perch.
02:39 The first thing to understand is the purpose of each of these adjusters.
02:43 So if I just crack off that lock nut there on the bottom mount, you'll see as I move the damper body, the entire assembly moves and what's happening there is this damper body is moving in and out of that lower mount.
02:53 The purpose of this adjustment is to set your wheel position when your suspension is fully compressed and also gives you some adjustment over where your suspension is operating within its travel when you're at its static ride height.
03:06 Now that'll become a little bit clearer as we move through the rest of the example.
03:10 The purpose of the spring perch here is to adjust your ride height.
03:14 We generally are not doing ride height adjustments here at the bottom perch, sorry we're generally not doing ride height adjustments here at the lower mount, we will generally always be doing our ride height adjustments here at the spring perch.
03:26 Now one of the misconceptions out there on this is that if you add preload to the spring which you do by pushing the spring collar up and compressing the spring, people think that you are increasing the suspension stiffness because you're adding preload to the spring.
03:41 That's not true, adding preload to a linear spring like we have here will not change its stiffness, that's a really important point to understand and something we did go over within the course body itself.
03:51 So the way we're going to approach setting this up, the first thing we want to do is make sure when the suspension is fully compressed, there's no way that the tyre or wheel can contact anywhere on the inner guard or the chassis or anywhere else where the tyre might be able to be damaged.
04:04 So when the suspension's fully compressed, if you've got a situation where the tyre can come into contact with the chassis or the inner guard, that can cause some really serious damage to the tyre and it's something we absolutely want to avoid, there's no way you want that tyre to be coming into contact anywhere with your chassis or inner guard, it can be really really destructive.
04:23 So the way we're going to do that is we're going to remove everything from the damper for a start.
04:31 Also going to remove our bump stop, now the reason we're doing that is we want to make this an absolute worst case scenario, we want to remove the bump stop so that gives us the worst possible case of how mechanically compressed the suspension can get.
04:42 So now we're going to refit that top plate there.
04:47 So now we've got our coilover ready to go, we're going to fit it to the car, we're going to put the wheel back on, we're going to fully compress the suspension, we want to make sure we've got no contact between the inner guard and the tyre.
04:56 Now if we do have contact between the tyre and the inner guard with the suspension fully compressed, the way we're going to adjust it is with the lower mount.
05:04 So we're going to crack off this lock nut here and we're going to wind the damper body like this.
05:09 That's going to make the damper body wind out of the lower mount and because this section is essentially rigid to the car at this point because it's fully compressed, what we're actually doing is pushing the wheel away from the inner guard.
05:22 So we're giving ourselves more clearance between the tyre and the inner guard.
05:27 Because the suspension's fully compressed, we know this is the worst possible case that we've got.
05:32 So once we've got to a position where we're happy with the position of the wheels, there's no way we can damage that tyre at full compression, we can then go ahead and lock up our lock nut again and we're happy with that position.
05:42 Then we're going to go ahead and take a reference measurement for how compressed the suspension is, so you can do this in lots of different ways.
05:49 You can have the wheel on there, you can be measuring from some fixed position on the chassis or the guard to your wheel position.
05:56 In this particular situation I'm going to find it a little bit easier to measure it from the hub to the ground, I think that's going to, in this particular case it's going to give me something a little bit more accurate.
06:06 But the important thing to understand, doesn't actually matter where you're measuring from, it's just that it does need to be a repeatable position that you can use.
06:12 We're going to take a measurement of the position of the wheel or hub with the suspension fully compressed.
06:18 Then we're going to do the same thing but with the suspension fully extended.
06:21 So we've still got everything stripped off the damper here but we're going to let it fully extend so we're in the full droop position.
06:27 So we're going to have a measurement, full compression, full extension, now we can go ahead and define our target ride height which as we talked about in the course, we usually want to be about 1/3 of the available travel so what do I mean by that? If we look here at the available travel on the shaft, let's pretend in this situation where the top of this damper here is equal with the top of the damper body.
06:47 That represents our full travel position, that means if this is the 1/3 position, that means at ride height we want this position of the damper to be sitting about down here equal with this point of the body.
06:58 That's going to reserve us approximately 1/3 of our travel available in droop and 2/3 available in compression.
07:04 Which as we talked about in the course is the approximate position we want to set up our car mechanically to have sufficient travel in both compression and rebound.
07:12 Now that we've got that target ride height point we want, we can go ahead and reassemble the damper so we can go ahead and adjust the spring platform so we get the suspension sitting where we need it to at our target ride height.
07:25 So we'll refit our bump stop, refit our spring.
07:30 Our helper spring in this case and our top mount and we can go ahead and make our ride height adjustments all on the lower collar as we talked about at the start.
07:39 So I'm going to go ahead now and carry out that process on this car here on the left rear corner.
07:45 So I've actually already got the spring and bump stop already removed from this corner of the car so we can go ahead straight away and check out tyre clearance at full compression.
07:54 Now I've got the wheel on the car, I'm going to go ahead and jack this corner of the suspension up and check for any interference between the surface of the tyre and the chassis and bodywork up here.
08:07 Now I've got the suspension fully compressed, I know that because if I jack up any more it's actually starting to lift the chassis with it.
08:13 So I know at this point the suspension and/or the tyre is totally bottomed out.
08:18 I've got the car in neutral and the brakes aren't on and I can feel really easily here that there's no way I can turn this tyre.
08:24 That means that we've got contact somewhere between the tyre and inner guard.
08:27 So from here the first thing I need to do is take that lower mount and lower it down so the tyre's no longer in contact with the car.
08:36 I've gone ahead and made that first adjustment and I can see straight away that it's much better, I do have some minor contact just with the guard back here and it's in a place where we aren't able to make an easy modification to the guard so I'm just going to go another step.
08:49 I just want to avoid any chance of that tyre coming into contact with that guard so it can damage it in use.
08:56 So I'm going to take the damper again and unwind the body from that lower mount just to get the wheel coming down a little bit further.
09:02 I've gone ahead and made that second adjustment and now I can really easily turn that wheel, I haven't got any contact in there, the only noise you might be able to hear there is just the noise of the diff plates moving inside the diff so everything in here is looking good.
09:15 Now we're happy with the fully compressed position of the wheel, what I've done is I've gone and put a piece of tape on here with a little mark.
09:22 That's going to be my reference I'm going to use for the wheel position at full compression.
09:26 So I'm just going to go ahead and measure from the bottom of the rim.
09:31 You can choose any point on the rim that's convenient for you, I'm just going to use the bottom here 'cause that's going to be the easiest for this particular type of rim and I've got a measurement of 555 mm exactly.
09:45 Now I can go ahead and drop this wheel back down to its fully extended or full rebound position.
09:50 I want to go ahead here and take the exact same measurement but this time with the suspension at full droop.
09:55 That measurement is 703 mm.
10:01 Now that I've got the measurement for fully compressed and fully extended, I can go ahead and calculate the wheel travel I've got at this corner of the car.
10:09 And then from that I'm going to calculate how much 1/3 of that travel is.
10:13 So the calculation I want to do here is I want to take the fully extended measurement and I want to subtract 1/3.
10:24 Approximately 1/3 of the travel available.
10:28 So this here is going to be the target measurement I've got when I've got the car sitting at its static ride height.
10:36 Now I've got the target wheel position I need when the car is sitting at its ride height.
10:41 So the procedure from here is we're going to put the spring and the bump stop back on the car and we're going to adjust this ride height with that spring perch.
10:49 Obviously we need to have the car sitting back down on the ground to do that.
10:53 So I'm going to go ahead and do that now.
10:55 Now I've got the car on the ground, I've got the spring and the bump stop back installed on the damper and everything in this corner back together.
11:00 You'll also see here I've got a couple of tile slip plates.
11:03 The idea behind that is as the car drops, because that wheel is moving through a slight arc and not vertically perfectly up and down, it allows the suspension to settle properly and not be held up in any way.
11:15 So now I'm ready to take my measurement. I'm going to see where we're at relative to our target ride height measurement.
11:21 So we are at about 645 mm and we're actually looking for 654.
11:31 So we're about 9 mm away from our target so what I'm going to go and do is jack it back up again and rotate that spring platform to raise the ride height.
11:40 At the moment we're a little bit low so that means we are a little bit too far into our bump travel so as far as that range on our damper shaft, if we want to be here, currently we're somewhere about there.
11:50 So we want to raise the car a little bit to get back in that 1/3 of the travel window.
11:54 I've gone and made that change, now I'm going to check my measurement again.
12:03 So we are bang on there at our target, 654 mm.
12:08 So remember the purpose of that ride height measurement, it's getting us back in that 1/3 to 2/3 travel range.
12:15 So we know now because we've measured the fully compressed position and the fully extended position of the wheel, because I've got that reference for 654 mm, in this case for this car, I know that if I set my ride height to that, I know that my damper is using roughly 1/3 of its travel when we're sitting at ride height.
12:32 So that's the procedure for going ahead and setting your coilovers properly, we've done this for the rear of the car, now we also need to go ahead and do it for the front of the car as well.