I wish I could find the paper that explains it better than me.

But basically, the centreline of the king pin axis ought to pass close to the mid-point of the tyre. If you imagine the wheels mounted further out, (reduced offset) it means the wheel has more leverage against the steering. Under braking on bumpy roads or uneven-friction surfaces, it means the wheel will tend to be dragged back more when it his a bump or a sticky bit. Obviously, it also works on suspension compression too, resulting in wheel jounce and increased bearing wear.

Since an S2000 effectively has four kingpins, reducing offset can produce some interesting handling characteristics. It's not really a problem on racetracks, since they are smooth. Which means the Big Brake Boys are less affected then the roadies.

It is possible to design a car with a low wheel offset. Nissan would be a good example. However, to get that axis acceptable, they need to use a lot of Kingpin inclination. Uehara was particularly critical of this, because a sloping kingpin creates a lot of 'jacking' as the wheel articulates (same reason why more caster does too), resulting in uneven steering feel & geometry changes, exacerbating bumpsteer.

So for road use, it's important to keep as close as possible to a factory spec. If you like that wonderful braking stability, consistent handling & a reasonable bearing/damper life.

 

Great information there, very interesting.

 

WHS. This is what I find now that I have much less rear toe. It doesn't feel as stable at the back as it used to, but the looseness is much more controllable.

BTW 2 degrees toe and now 1? I think with 2 degrees your rear tyres would have lasted 5 minutes, whereas the change now is that they'll last at least 10. Presumably Fatbloke has his numbers wrong. I have 10 minutes either side (i.e. 1/6th of a degree).

 

I thought I had a lot of toe at 30mins per side - this stems from my original request to Chris Franklin for a non slidey rear.

 

I had 30 mins rear toe in set up by WIM but went back and had it set to 15 mins due to excessive rear bump steer and tyre wear.

 

Thanks for the info folks. Very interesting.

I haven't had chance to get out in the car since the geo was done on Tuesday, but of course, I'll drive it and make up my mind (good thrashing planned for the weekend), I just wanted to get a handle on the 'physics'. I know what I like - I just don't know exactly what produces it, if you get what I mean?

From what you've all said, it sounds like the new settings will be more to my taste - as I said, I don't mind sacrificing ultimate grip for better feel and controlability.

Cheers,
FB

 

Rear toe is a sticky-plaster for a crap bumpsteer curve.
Static neg to alleviate the positive that creaps in under cornering - naff.

Get some proper adjustable toe arms on there and dial out most of the toe too.

All it does is rape the tyres, and make the car less pointy.
Its a Sports car, not a shopping trolley...

PS- NO WAY that WiM put +120' of toe on the arse of an S2000
I reckon you are confusing CAMBER and TOE ???

 

Only if you're a big puff who lifts the throttle mid-corner.

It's useful to adjust the line once you know it's there, for eliminating understeer entirely.

 

Sort of - not sure what I was getting confused with, but the actual figures were:

WIM: total toe 1 degree
New: total toe 32'

Camber was and still is 2 degrees each side.