Auto Service World
Feature   February 1, 2004   by Jim Anderton

Simple Strength

The basics of ball joint and rod end engineering haven't changed since the death of the kingpin. The demands on these safety critical components however, have never been greater.

It’s a ball in a socket. In many cases, that’s enough knowledge about ball joint and tie rod end science to get a vehicle’s steering and suspension in safe working order. It’s a simple technology at first glance, but like so much of modern automotive technology, there is more going on than meets the eye.

“Service” in this under car segment has some of the qualities of ride control replacement; in general, you’re replacing parts that are worn, as opposed to broken. Why do they wear? It’s not rocket science, according to Larry Sitzes, product engineer for Moog Chassis (Federal Mogul): “As the part wears there’s less material. Most service manuals say to check for looseness by lifting the vehicle to take the load off, then rocking the wheel. Some have a specification, such a 30 thousandths radial movement, up to as much as 100 thousandths of movement before it’s a bad part. Most in the service business would look for perceptible movement.”

Although tugging on a wheel to feel for play is still the first check most technicians perform, it is important to think about whether the part is loaded or not when the vehicle’s weight is off its wheels. “It depends on the suspension type”, says Moog Chassis product manager Joe Cirino, adding ‘even if it’s dangling free, on most parallelogram suspension types the spring on the lower control arm keeps the lower balljoint loaded. A follower balljoint would typically be unloaded with the vehicle in the air. An example would be Macpherson strut types.”

With the combined trends toward sophisticated sport sedans and SUVs, the market is becoming a mix of traditional and exotic technologies. Jeff Repaal, director, steering and suspension product development for the Spicer Chassis division of Dana notes, “rack and pinion took a part of it, wishbone suspensions and struts took some with the reduction of the upper ball joint, but with the influx of SUV’s, now you’re back into upper and lower ball joints. What went away is coming back.”

Repaal believes that rack and pinion systems will continue to move into traditional recirculating-ball system territory, namely trucks, taking away much of the centre link/idler arm and inner tie rod service common today: “Rack and pinion will be a bigger thing. You’ll see more of it on trucks. You see trucks today with inner ends hooked on to a ‘non-wear’ centre link, and some day there will be a rack in there.”

Once you’ve found the worn component, with what should you replace it? Dealer OE, name brand aftermarket and “white box” are out there, with the latter two forming the bulk of an independent’s replacement business. Dealerships naturally sell more O.E. parts, import dealers in particular. Yet major aftermarket players can supply parts that equivalent in performance, and quite often are identical to O.E. joints. Why are consumers easier to sell on dealer O.E. chassis? According to Ron Strain, program manager for Dana Brake and Chassis (Spicer), “that’s a tough message to get across. When you look at the import vehicle market compared to where it was in the late Seventies, we were selling (relatively few) vehicles per year. If you were one of the people who thought that import cars wouldn’t catch on, you felt that it wouldn’t be productive to carry import parts. Its been well capitalized by import car makers. Import car dealers took that negative impression (poor parts availability) and capitalized on it. Import car dealers still retain a high percentage of service vehicles for vehicles out of warranty.”

Winning the chassis business that stays with the dealer after warranty requires the ability to convince the consumer that the parts you’re installing are O.E. quality or better. Installing premium products helps, as does replacing factory “lubed for life” joints with greaseable parts. As modern polymer socket low friction joints wear out and reach the independent aftermarket, is the type of grease an issue with replacement joints that have nipples? No, according to Moog’s Larry Sitzes: “We see it more and more from the factory; vehicles do not have greaseability. It’s a good feature to have. On my own vehicle, they dried out, and began to make noise. I replaced them with ones that are greaseable. It was a squeaking noise between plastic bearings and steel studs. Most good grades of chassis grease are fine. For our metal to metal parts we’ve typically used a moly disulfide grease, but we’re looking at future greases that may not have molybdenum disulfide, but are a better grade grease.” Sitzes notes that mixing good grades of chassis greases with differing bases shouldn’t be a problem. “Most chassis greases are lithium based, and they’re pretty compatible”, he says, adding, “we’ve not seen parts, including those that are polymer type bearings, destroyed by grease. If a polymer bearing is destroyed, it’s typically because of sand and grit.” Sitzes cautions against using the same grease that’s specified for CV joints, noting that constant velocity units have a much greater grease capacity and a significantly hotter operating environment.

How much grease? Older wiper type seals allow flushing the joint with grease, but with most modern parts, visible grease at the seal is a problem, declares Joseph Cirino: “In most non-greaseable parts, like the full ball polymer parts, a split or crack is pretty detrimental. That does cause a lot of premature failures. It certainly justifies more frequent inspection.”

Ball joints and tie rod ends have traditionally been regarded as a ‘brute force’ brand of chassis service, where a delicate touch isn’t as important. That may change as new suspension technologies make their way into the aftermarket. Jeff Repaal relates: “I don’t think the technology has changed the work, but the performance of the part has changed. The response of the vehicle is more tied in to the part than it was in the past. It’s about low friction, lighter weight vehicles. The performance of suspensions today is far above what it was 10-15 years ago. You get a lot more miles out of a new style ball joint with sealed boots, for example. As far as the technician changing it, it still takes muffler guns to knock rivets off, hammers to knock parts apart.”

Will that change in a couple of years? States Repaal, “absolutely. You see a lot more aluminum out there today. Hammers and aluminum don’t mix.”

Does the relatively forgiving nature of this part of the chassis segment mean that ball joints and tie rod ends are a “no-brainer”? No. As Ron Strain says simply, “they’re not glamourous, but when you look at what a ball joint is supposed to do, it’s not something that you should take lightly. Tie rods are the same.”

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