Chassis development
Chassis development…or why is everybody telling me to get my car ‘Geo’d’?
So you bought yourself a nice, shiny Elise or Exige, and have driven the first couple of thousand miles? That’s the point where lots of owners are hit by the ‘go faster blues’ and either start investing in go faster parts, or walk away not knowing where to start.
In this article, I’d like to give some insights to the updates you can do to get more fun out of your car without the need to install a 200+bhp engine for starters.
One of the regular remarks on the forum is ‘get yourself upgraded’. Of course, driving and racing courses will make you go faster! Everyone who’s even a little active within the Seloc community knows the name Andrew Walsh (aka Walshy). He can sure help you to understand your car and make you go faster. Besides - it’s great fun to do!
Time to go for the first engine mod? Run out of possibilities to go any faster? Not quite! There are more possibilities to make you go faster without the need to improve the power output of your car’s engine. The trickery which makes this possible is Geometry. I can hear people say ‘Lotus is the best chassis developer in the world, so why would I fiddle around with their settings?’ The answer is as easy as it is logical - Lotus has created a car which needs to be everyone’s friend. It needs to be entertaining for the beginner but at the same time Lotus wouldn’t want to make its handling tricky. If you’re a bit further down the line, have built up track experience and have some training courses under your belt, you might opt for a bit more entertainment, so you could start playing with the geometry of your car. Before doing that, I’d advise you to buy your first upgrade: a stiffer and adjustable front anti-roll bar. This simple and relatively cheap upgrade will enable you to play around with the balance between under- and over-steer. (understeer, in which the car starts sliding over its front wheels while entering a corner; over-steer, in which the rear of the car attempts to overtake the front, ultimately resulting in a spin).
Mind you, the balancing act of the anti roll bar (ARB) will not improve grip. A lot of people hate under-steer and prefer over-steer as long as it’s controllable. Control is exactly what you can get by setting up the ARB. Another effect of this device is the reduction of body roll - that does improve grip! How does grip work? When you think of the four patches of rubber which are the contact of the car with the road surface, you can appreciate the basic grip of the tyre. The more sticky the tyre, the more grip you will have. Well not exactly - another thing you wouldn’t want is to lose the weight on one of these patches. If you do, that specific tyre will not be able to provide you with the grip you’re used to. Getting back to the ARB, body roll actually is moving the weight on to the tyres. If you steer into a corner, the mass of your car will want to move on in a straight line. This will cause the body to roll over the car’s roll centre. The less the body is able to roll, the more weight you will keep in the same place, so there you go - it will produce more grip in a corner and will help you to go faster! The next step to improve your feeling with the car could be to start fiddling with the Geometry of the car. To do so, you’ll have to understand the basics of Geometry. If you really want to understand what you’re doing and even want to do it yourself, I would strongly suggest you pick up the parts manual first and buy yourself a pile of shims. You will need them!
First, the basics. There are a couple of things you’ll need to understand first - All settings are measured per axle!
Toe-in / Toe-out
Looking on the axle from above, if the fronts of the wheels are closer to each other then the rears, this is called Toe-in. If the opposite is true, e.g. the rear side of the wheels are closer to each other then the fronts, this is called Toe-out.
Toe-out will produce high-speed straight line stability but will make the car a slow turner. You have to work harder to get into corners.
Toe-in will not help you for straight line stability. The car will be pretty nervous, but it will want to attack each and every corner. There is no such thing as the perfect setting for Toe-in / Toe-out. The ideal setting for a (semi)-professional race car driver might be horrible for you. Keep in mind, the more toe you set, the harder your tyres will wear!
Camber
You will now have to look at the wheel from the front or the rear. The camber can be called negative if the top of the wheels are closer to each other than the bottom.
Positive camber is the setting where the bottom of the wheels are closer to each other than the top.
Where camber is concerned nearly every possible setting, the camber will be negative. The only question is.. how far should you go? The effect of negative camber might be loss of straight-line grip. As you’re setting the surface of the tyre in an angle to the surface of the road, you are losing grip. But as soon as you enter a corner (which is the place where you lose most speed when track- driving), the surface of the tyre will deform and, when your setup would be 0 Camber, you’ll lose grip. Having the car set with negative camber, the road surface contact will actually increase in the corner, thus improving grip. Exactly what you want!