bump steer

[strad]

nice dodge
Don't worry, I've sorted it and can carve canyons better than 90+% of cars I come up against and that includes those from highly regarded marques ...

[strad]

And yes I realize I should have started with coil overs but The Eibach rep convinced me to go with their Sportline kit.
I've got it pretty well worked out, it's just that it's a better street racer than street cruiser.

[marcush.]

So we are deep into it again ...
first of all a car Setup should be trusty - as I assume all of us are not Ayrton Senna so we might be able to drive around Problems but that is certainly not quick by any Stretch...

this is Why stiff cars are quick btw -its not Optimum ,far from it -but usually it is very predictable and you can read what is going on with ease .How can you know that when you get no Feedback from your machine?
So the stiff Thing has a certain Response to your and the tracks Input and so the Limit is becoming something of an approachable border.

Back to the bump steer geometry - well if there is no bump in the Corner you will not even notice there is a quirk in your geometry . The Lotus Elise for example had its steering arms laid out wrong enough to actually kill the steering rod Joint on track days if you used just the tiniest bit of inside curb .it was just not designed for bump on the inside wheel when cornering .I guess that is an extreme example for bump steer as you get a nasty steering Input on top of the knock when touching the kerb .....very very bad .My view on this .Get a linear Response as much as possible or progressive - but linearity will always be a good starting Point as always -Keep it simple ,Idiot- is beating the überclever approaches dayin dayout....

As for a roadgoing racer -invest in a set of real dampers - sure those TTX or whatever they are called todays cost ridiculous Dollars but that´s the way to tame a street racer .with the Elise it was the only way to arrive at a Setup which was quick and felt driveable for normal street use.I agree it´s not in the Budget of 99% of the guys out there but it works.

[strad]

Thanks 'Cept they don't make them for Mustangs.
I have been tinkering with it for 12 years...It works great... The wife doesn't enjoy riding in it..If I hadn't recently pulled the plug I'd probably buy an F Type...

[Greg Locock]

strad, I just read back through. I was talking to the design team for the Cobra IRS as it was being designed simultaneously with our first Falcon IRS. At the time I was working on NVH and driveline so I was not much involved with the ride and handling side, but inevitably i did hear what they were doing. This is what we were designing at he same time as them, hopefully apart from the subframe the similarities are obvious

http://i1257.photobucket.com/albums/ii5 ... Ute135.jpg

In particular FNA are great fans of using wishbones with inboard mounts displaced in both Y and Z from their natural positions. They also did that to the Lincoln LS IRS which they designed just before the cobra. I am not a fan of weird wishbone angles, but then I think double wishbone back ends are not a great move anyway, if you've got serious power.

Since then we designed another one, and it looks nothing like the Cobra,
http://www.goauto.com.au/mellor/mellor. ... 940029A285

The somewhat odd subframe architecture of both of these is because they had to fit in the exact same space as our excellent beam axle.

Surely the reason that a good track car is not a civilised road car is that fundamentally a race car is 70% critically damped, whereas a road car is 30% (says Milliken, from memory).

A change of 10% in the damping force is subjectively significant, so a factor of more than two is going to be a huge step in the wrong direction.

[strad]

The somewhat odd subframe architecture of both of these is because they had to fit in the exact same space as our excellent beam axle.

And there in lies the rub.
The Ford Team tried to build a sub-frame to contain the IRS in the same space and wound up with poor geometry and some pretty weak mounting points. Had to install stiffer bushings and even weld in better mounting kit.
When I look at Art Morrison IRS sub-frame cradles he sells to bolt IRS into hot rods much the same way as a front clip or something I wonder about his geometry.