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Motorsport Wheel Alignment: Adjusting Anti-Roll Bars

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Adjusting Anti-Roll Bars

03.58

00:00 - One of the most common and potentially one of the cheapest modifications we can make to the suspension on a competition car, is to fit adjustable anti-roll bars.
00:08 These give us the ability to adjust the roll stiffness at the front and the rear of the car independently which can have a large impact on the handling characteristics of the car.
00:19 In particular this gives us a pretty easy way of adjusting the balance of the car to suit a particular track or to adjust the balance of the car to suit a wet or a dry track.
00:29 In general, an adjustable anti-roll bar isn't a particularly sophisticated device and these will usually have multiple attachment points at each end of the anti-roll bar where the linkage attaches between the anti roll bar and component in the suspension system.
00:45 The idea with the anti roll bar is that to stiffen the roll bar, we adjust the linkage so that it's closer to the centreline of rotation of the anti roll bar.
00:54 Conversely to soften the anti-roll bar, we move the linkage further away from the centre of rotation of the anti roll bar.
01:02 This is simply and adjustable lever arm.
01:05 One subtle aspect to keep in mind is that if we've got an adjustable anti-roll bar such as the one fitted to the rear of our Toyota 86, that has three location points on each end of the arm, we don't need to use the same adjustment location on both sides of the anti-roll bar, and this actually gives us finer control or adjustment over the stiffness of the anti-roll bar.
01:27 Now all of this should be relatively straightforward and easy to understand, one area we do need to be mindful of when we are making adjustments to our anti-roll bar stiffness is to ensure that the anti-roll bar doesn't preload the suspension when the car's sitting at normal ride height.
01:45 It's very easy for this to occur, particularly if we aren't using the same location for our linkage in each end of the anti-roll bar.
01:53 This has the effect of preloading the suspension which can make the car handle differently in left hand to right hand corners.
02:00 Preventing this will require a pair of adjustable anti-roll bar linkages which go from our anti-roll bar to our suspension system and what we need to do is adjust our anti-roll bar linkages so that when they are slipped through the anti-roll bar at the car's normal ride height, there is no preload.
02:19 In other words, they slip through effortlessly and we don't need to bend the anti-roll bar either up or down in order to fit the linkage through and then tighten it up.
02:29 Most people, when they are adjusting the anti-roll bar, will adjust these linkages with the car jacked up, which means that the suspension is at full droop.
02:38 And while it might seem that this is a sensible approach, we may find, depending on the weight distribution in the car and the way the suspension or coil over has been adjusted, that this may actually end up with the anti-roll bar preloading the suspension at ride height.
02:53 For this reason it is important to make our adjustments or check the anti-roll bar adjustment at the car's natural ride height.
03:01 And this can be a little bit more difficult than it sounds.
03:04 Particularly because it can be difficult to get under the car and access our anti-roll bar linkages with the car at normal ride height.
03:12 Now this really will come down to the design of your car and how easy it is to access those linkages.
03:18 If you've got a car where getting access to those anti-roll bar linkages at normal ride height with the car sitting on the ground is impossible, then the way around this is to lift the car up on a hoist and then lower it so that that wheels are being supported on a set of stands.
03:36 Obviously it should go without saying here that whatever you use to support the car, should be rated to the weight of that car.