Mike Smith of Dana/Spicer blames the decline of steering and suspension parts on the increased sales of new vehicles, improved durability of OEM parts and market shifts in the vehicle population.

"It’s not unusual to see a lot of import cars go to the scrapyard without ever having any significant chassis parts replaced," said Smith. He suggested a lot of these cars were essentially "disposable." Once they accumulated so many miles, may not have been worth fixing.

On the other hand, the growth of truck and SUV sales in recent years may help generate regrowth in what has been a relatively flat market. Over 50 percent of all new vehicles sales are now trucks and SUVs. Historically, these types of vehicles have been kept on the road for much longer periods of time than passenger cars. Whether this trend will continue or not remains to be seen, but if it does, it should eventually spur a rebound in the sales of traditional

steering components such as idler arms, tie rod ends and center links, plus chassis parts such as ball joints, bushings and springs.

"We’ve looked at the top 30 vehicle platforms to gauge the future demand for chassis parts. Right now, 60 to 70 percent of these vehicles are truck platforms with conventional parallelogram steering gears. At some point, a high percentage of these vehicles will need replacement steering and suspension parts," said Smith.

Smith estimates the current replacement market for steering and suspension parts (excluding shocks, struts and remanufactured steering racks) to be about $400 million a year. But in a recent report published by the Automotive Aftermarket Industry Association (AAIA), the estimated retail sales for all types of aftermarket steering and suspension parts (including racks and ride control products) is reported to be nearly $2 billion a year!

Regardless of whose numbers you use, there’s no question the chassis parts market is still a big one with plenty of sales potential.

Brian Rassin, product director of Moog Chassis Parts for Federal Mogul Corp., says he sees positive signs for future growth based upon the vehicle parc mix. "The growth of trucks and SUVs will stimulate additional replacement part opportunities due to the traditional steering and suspension configuration," says Rassin. "Truck owners, on average, spend more to maintain their vehicles than passenger car counterparts." On the downside, he said, "We’re seeing some new truck applications with rack and pinion steering. In 1998, Ford went to rack and pinion in the Ranger. In 1999, GM switched to a rack in the Sierra. Rack and strut systems are lighter, more compact and have fewer replacement parts, but how well these new racks will hold up in a rugged truck environment remains to be seen."

GM is also offering four-wheel steering (4WS) as standard equipment on the 2002 all-wheel drive Extended Cab Sierra Denali. It reduces the truck’s turning radius by nearly 10 feet, allowing it to turn as sharply as a Saturn passenger car. Quadrasteer also makes parking maneuvers easier and improves vehicle handling and stability at all speeds. But sooner or later, like every other part on today’s vehicles, the steering components will wear out and have to be replaced.

Rassin said the OEMs are also adding more suspension parts in the rear of many truck suspensions. The change to an independent rear suspension in the Ford Explorer and others adds rear ball joints/cross axis and bushings that will eventually have to be replaced.

Because many OEM parts last longer, it has delayed the traditional replacement curve. Rassin said he still sees some parts that need to be replaced after two or three years of service, but more are in the five to seven year replacement category – or longer. Consequently, this affects how long aftermarket parts suppliers need to provide parts for various vehicles. Rassin said Moog typically maintains minimum parts availability for passenger cars up to 15 years old, 20 years for light trucks and 25 years for medium trucks.

MARKET ISSUES
Though some people may see chassis parts as a "commodity" with little differentiation between brands, manufacturers insist there are significant differences in quality, fit and performance. Even so, price competition from offshore suppliers has been eroding market share from traditional domestic suppliers in recent years.

"It’s an ugly market," said Rassin. "So we have to offer leading-edge premium parts that are differentiated from the rest."

One new technology that is available from Moog is M2. "We have had great success with M2, and now an enhanced and patented version of M2 is soon to be launched," said Rassin. It is a combination of unique design and manufacturing processes that allows metal ball joint and tie rod ends to have reduced friction characteristics that are better than those provided by current original-equipment polymer designs. This performance enhancement is layered on a foundation of the Moog "problem solving" heritage of being easier-to-install and fixing original equipment design problems.

GENERATING SALES
The rate at which steering and suspension parts have to be replaced depends directly on miles driven. The more miles a vehicle accumulates, the more wear and tear you’ll find in ball joints, tie rods and the steering gear or rack. And the heavier the vehicle, the more it pounds its suspension.

Most motorists may not realize their vehicle needs steering or suspension parts. Unless the steering feels loose, pulls to one side or is causing abnormal tire wear, they have no way of knowing if parts are worn beyond specifications or not. That’s why professional installers need to pay close attention to the steering and suspension components when servicing their customers’ vehicles. This is especially important with vehicles like SUVs that have a high center of gravity. Worn steering or suspension components undermine safe handling and may increase the risk of a rollover in certain situations.

Technicians need to check things like ball joint play; tie rod play; idler arm play; the condition of the control arm bushings; the condition of the shocks, struts and springs; and ride height in the front and rear. If the vehicle has an independent rear suspension, they need to check all of those components too.

PARTS THAT AFFECT TIRE WEAR
Uneven or rapid tire wear is often the result of worn steering or suspension parts. Toe wear is the most common type of wear seen on front tires. It produces rapid tread wear that typically leaves a sawtooth or feathered pattern across the tread. If you rub your hand across the tire one way it feels smooth, but it feels rough when you rub it in the opposite direction.

Toe wear is caused by toe misalignment, which in turn is usually due to worn tie rod ends in the steering linkage. On vehicles with rack and pinion steering, it can also be caused by worn inner tie rod sockets. Other causes include bent steering arms and bent tie rods.

The outer tie rod ends typically experience a lot of wear because they twist and turn with every steering motion, as well as flex back and forth with every gyration of the suspension. The right tie rod end is often the first to wear out because right hand turns tend to be sharper than left hand turns. Their location near the wheels also subjects them to road splash. Over time, water and dirt can seep past the boot seal and contaminate the grease inside. If the tie rod ends are the greaseable type and have not been lubed at least once a year, contaminants will accelerate joint wear and increase the play even more.

Another type of wear that is often seen on tires is camber wear. This typically produces heavy wear on only one shoulder of a tire (usually the inner shoulder). This is caused by camber misalignment, which in turn can be due to worn or collapsed control arm bushings, worn ball joints, weak sagging springs, a bent steering knuckle or spindle, strut misalignment or damage, or structural damage or misalignment in the engine cradle, subframe or strut tower.

When rapid or unusual tire wear is discovered on a vehicle, the steering linkage and suspension should be carefully inspected to determine if any parts are worn or damaged. If everything checks out okay, realigning the wheels should eliminate the problem – unless the vehicle has structural problems in which case additional repairs would be needed.

Tie rod ends can be replaced individually or in pairs. Many technicians prefer to replace tie rods in matched pairs because they know if one has failed, the other is probably nearing the end of its service life, too. Left and right tie rod ends are usually threaded differently, so make sure your customer gets the correct side if only one is being replaced. You might also recommend new tie rod sleeves if the steering linkage has these because old rusty sleeves can make toe adjustments very difficult.

Another often overlooked cause of front toe wear on vehicles is rear axle or wheel misalignment. If the rear wheels are misaligned, it creates a thrust angle that causes the vehicle to lead to one side. The driver has to counter this tendency by steering a little to the opposite side. Thus, an off-center steering wheel is a good clue the vehicle has a rear steer problem possibly due to worn parts.

Rear wheel misalignment can be caused by worn suspension control arm bushings, weak springs, or damaged or mislocated suspension parts. On vehicles with independent rear suspensions, rear toe adjustments may be provided to correct rear wheel alignment. But if no factory adjustments are provided, your customer will need some type of aftermarket alignment kit to make the corrections. On front-wheel drive cars and minivans, rear axle shims are often needed to make such corrections.

DON’T FORGET THE SPRINGS
Springs may not wear with age, but they do sag and occasionally break. After six or eight years of fighting the forces of gravity, it’s not unusual to find springs that are at, or below, minimum ride height specifications. That’s why technicians should always measure ride height prior to checking wheel alignment and when investigating steering and handling complaints. Ride height affects wheel alignment, vehicle stability and the suspension’s ability to handle normal loads and overloads.

Spring shims are a quick fix for restoring ride height, but they do not restore spring rates or ride quality. The recommended fix for sagging springs is replacement – with new stock springs, heavy-duty springs or variable rate springs. Heavy-duty springs are a good upgrade for vehicles that are used for towing or hauling heavier-than-normal loads. Variable rate springs are a good choice for cars and trucks that may need some extra load carrying capacity on an occasional basis. The advantage with variable rate springs over heavy-duty springs is that they don’t increase ride harshness when carrying normal loads.

Other suspension upgrades to improve load carrying capacity include air shocks, air springs and helper springs. If a DIY customer is buying a trailer hitch, ask him what he’s going to pull with it. Then recommend any suspension upgrades that may be needed to handle the payload.