Niagara Gazette

February 17, 2014

TOM'S CORNER: Tom dispenses shock and strut wisdom

By Tom Torbjornsen
Niagara Gazette

Niagara Gazette — RON FROM DOVER, DEL: I own a 2003 Toyota Solara. How often should the struts be changed? And are struts a lifetime part?

TOM: Strut life varies with the type of vehicle, how the vehicle is driven, and the environment in which it is driven. Have the struts inspected by a qualified shop to determine if they need replacement. Struts do not last the lifetime of the car. As a matter of fact, as far as the car warranty is concerned, they are considered a wearable item that must be replaced as a part of regular vehicle maintenance and thus, are not covered under the new car warranty. However, in certain cases if the shock or strut is damaged by an item covered under the new car warranty, shock or strut replacement may be covered under the warranty repair. Each case is different and up to the discretion of the warranty.

Ron asks a couple of great questions that a lot of people ask. Let’s take a look at other questions I get related to shocks and struts.

What do shocks and struts do? Shocks and struts are designed to dampen vehicle suspension spring oscillation for safe handing of the vehicle, plus they keep the tire firmly planted on the road surface enabling proper cornering and handling. Some shocks (mostly for trucks and off-road vehicles) are referred to as anti-roll shocks. These are designed to force the suspension downward when the wheel goes down into a road depression. This keeps the vehicle body stable and stops body dipping. Anti-roll shocks originally were developed for ambulances to keep the vehicle body stable when transporting patients laid out on gurneys. Apparently too many patients were rolling onto the floor when the ambulance driver took a turn too fast.

What happens when they go bad? When shocks and/or struts go bad, a few things can happen. Vehicle handling is negatively affected. Instead of firm, safe cornering & handling; the vehicle tends to become a bucking bronco. While driving down the road, if the vehicle hits a bump or pothole, it will bounce one way and then another. The smallest roadway imperfection will cause the vehicle to handle very roughly. Another thing that happens is that the tires tend to display choppy or cupped wear on the outside edges of the tread, it almost looks as if someone scooped out rubber with a spoon all along the edges of the tires. This causes a rough whirring sound as the tires roll, plus they wear out prematurely. Finally, because the suspension spring oscillation is not held in check, excessive wear to other suspension and steering components occurs.

What is the proper method used to inspect struts and shocks? The proper way to inspect a shock or strut requires lifting the vehicle off the ground and visually inspecting the shock or strut body. Evidence of oil leaking indicates the need for replacement. Why? Because the gas charge injected at the factory is mixed with oil to lubricate the inside of the unit. If oil is leaking out, then the seal is broken and the strut or shock is no good. Other causes for replacement are excessive rust on the strut or shock body, damaged or scarred rams, broken shock or strut mounts or bushings. Another simple way to check shocks and struts is to perform a bounce test. Place your knee on the bumper of the vehicle and start bouncing the body. Once you get it going, step away from it and watch how the body reacts. It should bounce half a time and settle to a stop. If it keeps bouncing, the shocks or struts are bad and need replacing.

What about air shocks or struts? How do I check them? Air ride suspensions use either an air compressor and feed lines to keep the vehicle level at all times, or no compressor is used and air is manually fed into the system at a central air valve. Either way you still have the basics of each system that can go bad; air lines & valves or the shock or strut itself. Typically air lines are made of plastic and over time wear out due to constant flex and/or exposure to the weather elements. A simple air line check will reveal where the leak is and what line/s have to be replaced. Over time, the rubber air bladder in the shock or strut degrades. When this happens, the unit leaks air and must be replaced. On the fully automatic systems, ride level sensors are used to measure vehicle ride height. When the vehicle load goes down to a certain point, the sensor sends a signal to the air compressor to charge the system with air, bringing the ride height back to spec. When this sensor goes bad, it must be replaced to ensure proper vehicle ride height. Finally, when an air compressor goes bad, it must be replaced to restore system operation. In some cases where air ride system repair is just too high and the owner does not what to spend the money, air systems can be removed and replaced with standard equipment. Repairs of this type are done on a case by case basis because replacement part availability & price varies with year, make & model vehicles.

Can you just replace the shock or strut mounts? In some cases, when the strut mounts go bad, it can cause a bang when going over bumps. The strut itself might be good, but the rubber in the mount has gone bad, expressing itself in the offending noise. Some front strut mounts have built into them bearings, which allow the strut to turn right and left when the car turns. Some rear strut mounts can be replaced as well, it all depends on what year, make, model vehicle. If no replacement mounts are available, struts and shocks must be replaced when the mountings go bad.

Should I align the car after replacing the struts? Yes, mainly because the installation process can affect alignment angles due to some suspension disassembly. At the very least put the vehicle on an alignment machine to check alignment angles after installing struts just to make sure it’s within factory specs.

Are struts a lifetime item? No, shock and struts are wearable items and go bad over time. Some replacement shocks or struts come with a lifetime guarantee, but I’ve never seen one continue to deliver proper service ad infinitum.

What is the recommended replacement interval for shocks and struts? They should be replaced every 50-70K miles or when the vehicle starts to handle roughly, fails a visual inspection, a bounce test, or tires show choppy wear patterns.

‘Til next time ... Keep Rollin’

“America’s Car Show” with Tom Torbjornsen airs 7:30 p.m. Wednesday, 9 a.m. Thursday and 11 a.m. Saturday on WBBZ-TV.

"America's Car Show" with Tom Torbjornsen airs 7:30 p.m. Wednesday, 9 a.m. Thursday and 11 a.m. Saturday on WBBZ-TV.