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Practical Corner Weighting: Slip Plates

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Slip Plates

02.33

00:00 - As we've already discussed, one of the problems with corner weighting your car is that every time we jack the car up, in order to make a ride height adjustment, the suspension will need to be settled after the car is lowered back onto the ground, otherwise we'll end up with inaccurate results.
00:15 One of the reasons this occurs is that the suspension naturally moves in an arc so when the car is lifted into the air and the suspension ends up at full droop, the wheel track is essentially narrower than what it would be at normal ride height.
00:29 When we now drop the car back onto the ground, the tyres contact the ground at this reduced track width and since they can't easily slide along the ground it makes it hard for the suspension to move back through its arc to its normal track width.
00:43 If the car is fitted with rubber suspension bushes, this process will also cause the bushes to distort when the car is lowered back onto the ground which can affect the accuracy of any alignment settings too.
00:55 One option for settling the suspension which we've already covered is to push the car back off the scales a meter or so and then push it back on.
01:03 Another option however is to use slip plates.
01:05 Slip plates are essentially two pieces of sheet metal with a low friction film or coating between them that are positioned under the tyres.
01:13 Slip plates allow the tyres to move relative to the ground as the car is lowered, preventing them from binding and allowing the suspension to return easily to its natural position.
01:24 There are plenty of options for commercially available slip plates however you'll be expecting to pay somewhere in the vicinity of $400 - $600 USD.
01:32 At RaceCraft, we use the BG EZ slip plates which also give you the ability to accurately turn the front wheels through 20 degrees of movement which is an important part of the caster measurement process.
01:44 You can however make your own slip plates using two square pieces of thin stainless steel sheet with a film of lubricant applied between them.
01:52 This is something you should be able to have any local sheet metal specialist cut for you quite cheaply and they're also easy to transport.
02:00 When we are corner weighting the car, we can put these slip plates onto the scales and then drop the car onto the plates.
02:07 Providing the slip plates are cut to the same size, then their weight will be equal so they won't actually affect our measured corner weights, however if for some reason your plates aren't the same weight, you can zero the scales before lowering the car onto them.