Suspension - "You can never have enough."
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Stock 1600's are supplied with a McPherson strut front end and a trailing
swing arm rear. The front suspension setup ain't that great for offroading,
as any large obstacles will tend to try and rip the radius arm from its
mount. Short of redesigning the entire system (why don't you just
build another car?) you're limited in what you can do.
The first step is obviously to beef everything up. Whilst doing this you should take into account the idea that you should increase the ground clearance of the car. If you drop longer struts into the front end, you'll have to lengthen the radius rods and lower control arms dimensions to maintain the original camber/castor settings. As the car is going to be raced then the opportunity also exists to increase the camber settings (to hell with excessive tyre wear). To this length the car is now fitted with adjustable struts and lengthened lower control arms (20mm). The radius rods have also been lengthened to improve castor, although this is simply a matter of a few washers. Note the "helper" spring on the strut (the flatter yellow one, between the silver collar and the yellow spring coupler). This sits just above the adjustment collars and is designed to absorb the high frequency oscillations of the wheel assembly. Front shocks are Tokico Gold's, however we have a set of adjustable Koni's that will also fit (however they have a shorter travel - so we'll probably only use them on bitumen). |
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The adjustable strut is quite easy to fabricate. Just take your
stock strut and grind off the spring retainer/locator. Source a set
of matched threaded sleaves/collars and weld the sleaves onto the struts.
Just make sure you position them correctly (based on spring and shock lengths,
and required ride height variation). You'll also have to fork out
some dough if you want some spring couplers, or spin up your own (like
we did).
This is a picture of the adjustable strut top mount. The basis of the adjustment is by rotation of the central aluminium plate (complete with rose-ball). Obviously different positions offer varying degrees of both camber and caster. It's just a matter of finding the best compromise between both. Note that if you don't use these, the dampers will have a rather nasty habit of disassociating themselves from the strut cap. |
The rear swing arm is more akin to the types of suspensions that the front end of buggies come standard with. This semi-trailing (because the pivot's aren't quite parallel to the wheels line of motion) arrangement has its advantages and its disadvantages. It's quite good at getting the power down to the ground and the independent rear always leaves the entire wheel footprint in contact with the road surface (good traction). The disadvantages are the excessive force exerted on the springs and the obvious use of uni's/CV's to get the power out from the differential. It doesn't take long for a new set of springs to collapse under the strain of offroading when used in a suspension setup like this.
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What we have thought of doing (short of drastically modifying
the rear suspension setup again!) is to use some coil-over shocks in place
of the existing shocks. Obviously the pic on the left is just for
show, but I think you get the general idea.
We'll get a simple cup spun up to hold the lower end of the spring just below the seal and then fabricate a second cap to locate the top of the spring just under the tower mounting point. This should improve the spring rate of the swing arm considerably, not to mention the fact that it won't collapse anyway near as easily... |
