The basic job of the suspension spring is to support the car and any associated loads. They also prevent brake dive, body roll, rear end squat on acceleration and generally provide an even ride. When it comes to tuning your suspension the choice is basically between lowering springs that reduce the ride height of your vehicle and performance springs that will optimise the handling of your vehicle. The suspension tuning option is down to you and your needs. Do you want your car to achieve admiring glances from onlookers when out on a cruise, if so then lowering suspension springs maybe just right for you. Alternatively if the odd weekend track event is your thing then mild performance springs will be better suited to the job.
There are three general spring designs available – Normal, Step Linear and Progressive Springs. The Normal Spring has equal spacing between each coil and the response rate is a specific designation when compressed. For example a coil spring with 200mm spacing between each coil in normal state with extra weight applied to the load will compress evenly at say 170mm apart. A further increase in the load would result in increased compression to say 150mm but again this would be even between each coil.
Step Linear Springs have one half of the coils at one spacing and the other half at a smaller spacing. As the springs compress the coils with a smaller spacing close up and become ineffective leaving the coils with the larger spacing to do the work. This set up provides different levels of response and performance. Linear springs are more often used in drag racing, road racing, track and races that require a high spring rate, in which a constant spring rate is more important than a smooth ride.
Finally progressive springs have different spacing between coils. When the spring is being compressed the top 25% of the coils touch and become ineffective, the more compression applied and more coils touch again becoming ineffective and the spring stiffens. Progressive springs are very sensitive to road defects but provide the stiffness required under braking and steering. Progressive springs are most likely to be found in aftermarket performance kits giving a blend of performance for street and strip.
Author Andrew Whitehead – a self confessed petrol head has owned numerous classic cars from fully restored to basket cases! He now has a website to fuel his passion in all things auto for more information on suspension tuning please visit http://www.onlyautos.co.uk/blog