Kozy

Interesting stuff, I've always been interested in the S2000 but never really fully understood its flaws dynamically. I was lead to believe it was a problem with the rear steer effects so that when the throttle was lifted in a corner the rear wheels toe'd out, so in effect to keep the rear planted in a corner you had to keep the throttle applied, obviously requiring a more committed driving style than a lot of buyers were capable of... resulting in a lot of crashes and complaints that it handled badly. Does this sort of tie in with your explanation on the rebound reaction? Can it be properly fixed?

Uprate front bar = More front roll resistance = More front axle load transfer % = More understeer. Uprate rear bar = More rear roll resistance = More rear axle load transfer % = Less understeer. He claims that shouldn't happen on paper, but it does.

On paper, that works perfectly!

Yep, think you've got me there with the bolts. Was single mindedly considering double wishbone adjustment via top arm.

Scrub radius as I understand it, is the distance between the point described by the SAI's intersection with the ground and the centre of the contact patch in the lateral plane. If you change the SAI by 1° by moving the upper ball joint inwards towards the vehicle, would you not alter the angle of the wheel too, and therefore leave the SR unaffected? For the SAI to affect scrub radius, would it not need to be adjusted independently of the wheel angle, i.e changing the angle between the SAI and the hub plane on the spindle? Maybe I have my definition of SAI wrong which is confusing matters, it is the angle between of the line through the upper and lower ball joints and the centreline of the car is it not?

Yes tyres are certainly a bit of a black art. As far as I have learnt though, it is generally accepted that load transfer results in a loss of grip on an axle due to tyre load sensitivity. More roll resistance at one end, either from springs, dampers, geometry or bars, will result in more load transfer at that end with a resulting reduction in the total lateral force available from that axle. Not arguing experience of course, if you have fitted a front ARB to a Focus and found increased oversteer then fair enough, however I added a large rear bar (from 14mm to 24mm) on my Civic and found it greatly increased oversteer, thus I would expect a front one to increase understeer. Different chassis and suspension designs admittedly, but this is what got me wondering whether this trait was specific to the Focus...

If there is no camber gain built into the suspension and the wheels are at 0° static, when the car rolls 1° the outside tyre camber would be 1° positive. Negative camber migration might be different terminology for the same thing, I'm not sure...

I wrote these a while back on one of the owners forums I frequent, the chap running this blog spotted them and asked if he could publish them to which I happily obliged. Handling basics - Tyres and load transfer Handling basics - Springs and dampers

Sorry for digging up old topics Tony, but could you expand on this comment a bit? Are we talking about the Focus chassis specifically? Based on load transfer alone a front upgrade would generally increase understeer, how do the geometry effects counter this to produce oversteer?

Are they not inextricably linked though? As far as I know, the scrub radius is what gives you the effects you mention but is tricky to measure, RFL is certainly a far more convenient method of checking. But it will tilt the wheel too so RFL should remain unchanged?

Strange, I always thought cars were best off with a positive (nose down) rake angle, certainly for aero at least. But then I am used to FWD shopping cars so that may sway things a tad...