Anyone willing to venture what the conventional wisdom is for the KPI on rear IRS uprights. I am taking a stab at say 4 to 5 degrees should give good geometry for fabricated rears using Sierra hubs.
Thx all
Alf

kingpin isnt that important on the rears, is it? its main affect is on camber change when the front wheels are turned. its effect on wishbone geometry is minimal surely.

The only significant effect it will have on the rear is helping determine the top wishbone length relative to the bottom. As long as your camber change is ok it should be fine. I copied the front kpi on my rear uprights.

LIam

Gotcha, thanks

There's no such thing as KPI on the rear upright (unless possibly on one of those Honda 4W steer cars).
If you're talking about camber, then it will probably fall between - .10 degrees to - 1.0 degress.
Incidently, a friend who worked for many years in touring cars here, told me the Nissans ran CVs at the outer ends of the live axles. They would then wedge the outer bearings to gain some neg camber. The half shafs would just flex enough to cope!

Rorty, I stand corrected. I was loosely trying to establish the relative vertical positions in space of the upper and lower upright pick-up points. Will play with the old string computer to optimize I guess.

Does castor not have an impact on the rears on whether the drive/ braking forces act on a push or pull much like a shopping trolley? Never ventured into this thought before but would +ve castor be more stable at accelerating and -ve castor more stable under braking? Any experts out there?

rear caster - the whole back end of the car follows the front like a great big castor.... seriously the castor effect needs a pivot so unless you've designed in some rear steer......
cheers
Bob