Can I calculate toe change before fitting springs?

[Matt Scarbro]

I'm having some Koni shocks and matched H&R springs fitted shortly and would like to reduce the rear toe in at the same time.

I'm aware lowering will add yet more toe in, so I'm hoping to calculate in advance what shims I'll need.

Or is less of an exact science than I thought?

I'm not expecting perfectly matched and exact toe figures but have a ball park I'd like to shoot for.

Current toe in is 0*18' per side.

The H&R springs lower 20mm from the current Cup chassis.

I would like to end up at about 0*05' toe in per side.

Ive done a fair bit of searching and reading but haven't concluded much, any pointers?

 

[tombate911]

When I lowered mine to the height you saw it at (Cup setting) I ended up with 0*30' of toe in per side.
Stardard being 0*15' per side
I fitted 30' shims to both sides. however even though the shim in 30' in effect it doesn't quite give you that amount of adjustment as some of it is translated into camber actually 0*28 toe and -0.08 Camber from the 0*30 toe shim to give you an idea. Those figures work out on a car that is set at the Cup ride height.

 

[Matt Scarbro]

Thanks for the input Tom, trying to piece it together, I have got the matrix saved for camber and toe effect from the different shims.

Do you know how much lower than OEM Cup suspension youR settings are or is that what you meant by Cup?