Suspension thoughts part 2

As mentioned, the suspension wishbones are going to be all new, mainly to preserve the longer wishbones at the back. So, armed with the Haynes manual, the Saturn modifications and some clever Google searching, I came up with this;

First stage, front wishbones. Looks like Saturn use the same mounting points for the wishbones top and bottom. The front upper and front lower jigs have length dimensions, and the width dimensions are dictated by the brackets and the upright fixings. So I'm happy I have everything I need there.

Rear wishbones. Now these are going to be fun! So as far as I can tell, the Saturn plans don't contain length dimensions for the wishbones, so they're no help. The Haynes plans do contain dimensions but for Sierra based uprights. So a bit of creative thinking is needed. The lower wishbones are quoted to be very similar to the Haynes wishbones,which are 381mm (centre to centre). The wishbones brackets on the chassis are 265.5mm from the centre line. That means the lower outer fixing for the upright is 646.5mm from the centre of the car. I think that is a good starting point, which means I need to make the new wishbone the same dimensions as the Haynes wishbone, but with the layout the same as the Saturn wishbone.

Here is a picture of a rear upright from a mark 1 MX5;

Unfortunately it's from a US site so everything is in inches. Converting to the metric system, the top measurement is 149.225 mm and the bottom is 114.3 mm. In basic terms, it means on the upright side, the top wishbone has got to end approximately 35 mm shorter than the bottom wishbone.

So, back to the Haynes manual. The bottom wishbone mounting point is 265.5 mm from the centre line. The upper wishbone mounting point is 301 mm. So on the chassis side, the top wishbone has got to be 35.5 mm shorter than the bottom wishbone.

This means that the top wishbone has to be overall 70.5mm shorter than the bottom wishbone. With the bottom one being 381mm, that means that the top one needs to be 310.5 mm long. That is 50mm longer than the original Haynes wishbone, but probably double the length of the Saturn wishbone.

Of course, there is the added complication of the rear driveshafts. I already know I need to alter the propshaft, I didn't want to have to adjust the rear driveshafts as well. Maybe I ought to wait for my donor...

The suspension brackets have now arrived, so I can at least get them fitted. Although I still have the whole rear suspension area to fit... and the diagonal bracing... and fully weld the chassis... and do the aussie mods... I'm glad I'm treating this as a fun hobby rather than a career!