The Evolution of Suspension Systems

There are a lot of differences between race cars and consumer sports cars, and the suspension system is probably the biggest.

Many parts elevate a racing car above a consumer sports car, but not all of those parts reside in the engine compartment.As a matter of fact, the biggest differences between your run-of-the-mill race car and your run-of-the-mill consumer sports car are:

1. Race cars don’t have sound deadening materials anywhere, so they’re loud as hell
2. Race cars don’t have any creature comforts like leather upholstered seats, air conditioning, 8 speaker surround-sound s tereos, etc. Just a hard, uncomfortable seat, a steering wheel, a racing harness, and a couple of pedals. The fire extinguisher is the only “extra.”
3. Race cars have aggressive, tight suspension systems that ride rougher than a milk wagon. Of course, they also allow for unparalleled handling

What follows is a quick little primer on suspension systems – great background info for any auto enthusiast.

The springs, shock absorbers and the assembly that connect the wheels to a vehicle is loosely called “the suspension.” The suspension serves two key purposes:

1. Keep the wheels on the ground
2. Make sure the vehicle is stable at operating speeds

However, in a passenger car, there’s a third purpose – do #1 and #2 as comfortable as possible.

In regards to “keeping the wheels on the ground,” the importance of this task can’t be understated. When your vehicle encounters a nasty pothole and 40+ mph, the wheel(s) that enter that pothole want to jump righ up in the air. Yet because the suspension springs can “push” the wheels back down to the ground immediately following the impact, your car stays under control.

What’s more, all the force of that impact is dissipated almost instantly. This is because the suspension’s shock absorbers control the rebound of the spring and keep it from upsetting the balance of the vehicle…which addresses function #2.

Now as far as function #3 – doing #1 and #2 while riding comfortably – there have been a lot of different setups used over the last 100+ years of automotive history. Here are some of the highlights:

The solid axle. The first type of automotive suspension that was produced in mass was the solid beam axle. With the solid beam axle the front wheels were simply connected to each other by one solid axle. This kind of early axle can still be found today on heavy-duty trucks and some SUVs. This is because that, even with the addition of several newer suspension developments, the solid axle is still very practical in many situations. Because the axle is so simple, it’s easy to maintain and very strong. The downsides to the solid axle are:

• The sheer size of the axle makes it difficult to incorporate into small or medium-sized vehicles
• The axle’s mass increases the unsprung load on the suspension, which in turn means that stiffer springs must be used, which means that the solid axle doesn’t ride very nicely
• The solid axle also increases the amount of bump steer which makes a car harder to handle

If you own a big, heavy-duty truck (think bigger than an F350/3500HD), or if you’ve got ambitions to rock crawl, you’ll want a solid axle. Otherwise, there are better alternatives.

The MacPherson Strut. An advance in suspension systems was the MacPherson system developed in the 1970’s. Although it’s a great suspension for regular old passenger cars (an elegant combination of performance of inexpensive components), it’s not ideal for racing cars. The reason? The MacPherson strut suspension has to change camber and/or move in and out whenever the wheel moves up and down…which really reduces cornering ability.

The Double Wishbone. The double wishbone suspension (a.k.a. double A-arm suspension) is a very capable race suspension. In it’s simplest form, the suspension is comprised of upper and lower A-arms that attach to a knuckle, which then attaches the wheel. By changing the design of the knuckle, the length of the A arms, etc. the suspension can be tuned to suite an infinite number of applications. This is the type of suspension used in almost every advanced race car today.

Tires. Tires aren’t commonly thought of as a “suspension” component, but they should be. In fact, tires are the most important suspension component on a car. Tire sidewalls must absorb impact without flexing during cornering. Tire tread must maintain contact with the road surface despite cornering loads, imperfections in the road, etc. Finally, the tire must stay “sticky” without getting too hot and breaking down.

If you want to pinpoint the most important suspension designs of the last 50 years, most of them came from the tire industry. But that’s another story…

Author Dan Nielson is a contract electrician and blogs for truckspring.com, a site that specializes in suspensions for trucks. They have everything from Bilstein shocks to firestone airbags.