Summary

00:00 - Does caster give any real effect on handling performance of a car? Yeah so there are a few different effects to caster.
00:06 I don't know David if you caught my explanation at the start of the webinar.
00:10 Obviously it affects the amount of steering feedback, the steering weight.
00:13 So what I mean by that is for a given amount of cornering force, let's say we're cornering at 1G for argument's sake, there'll be a certain amount of lateral force in the tyre and the mechanical and the pneumatic trail on the tyre will determine the moment arm over which that, how much steering torque you end up with as a result from that lateral force.
00:33 So that is absolutely affecting the amount of steering torque the driver will be experiencing for a given amount of cornerning force.
00:42 The self centring and that stability is a big part of it as well so that means, a lot of you guys will be familiar with this, you go and put some steering input on your road car and you let go of the steering, you'll notice straight away that the steering wants to self centre, it wants to come back to a straight position and that's what Dave's talking about there with self centring, the more caster you have, the more self centring ability you have as well, the quicker or the more aggressively it'll want to self centre, that's another affect.
01:05 But probably in terms of the car setup and the handling, the most important one is that one I talked about before which is in terms of it changes the amount of dynamic camber gain as well that we get so if you have zero caster, the camber you have when you steer the front wheels is going to be exactly what you set as your static camber.
01:20 The more positive caster you have, the more dynamic camber you're going to have so if we have a whole lot of positive caster, when we add steering input, we're going to gain a huge amount of negative camber as we turn that front axle.
01:31 So the important thing to understand there is you've got lots of different cornering phases so in particular on the front axle because we're turning the front, we're not obviously steering the rear, so that dynamic camber balance between the front and the rear axle, so there's different phases of the corner, the amount of caster you're going to have is going to have a big influence on your mid corner, well balance throughout the whole cornering process really but usually the one we're most focussed on to start with anyway is at the mid corner.
01:55 So definitely Dave, caster is a big big tuning tool.
02:00 It's not usually something we are adjusting all of the time at the track.
02:04 It tends to be something, because it has so many other flow on effects when you adjust it, it tends to be something we set at a starting point and tune around it, it's not something we tend to be changing every session.
02:14 Certainly there's times when you add more or less caster to the car but because when you change it, it has all these flow on effects you have to completely redo the setup because of it, it tends to be things more like camber and toe that we tend to spend more time on and maybe just change things like caster between race weekends.
02:28 Usually not so much during, unless it's maybe one of your test points that you want to check.
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