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Fully restore damaged front suspensions

Tuesday, November 28, 2017 - 08:00
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When customers evaluate shop performance, they tend to lean most heavily on two sensory responses, look and feel. Shops focus heavily on the first as they return cracked, bent and broken finishes and parts to factory specs using the latest technology and training. This focus makes sense. The first thing customers are going to notice in a repair is the vehicle appearance. 

Feel can be just as significant. In fact, in the days and week that follow a repair it can surpass look. The feel here is the responsiveness of the vehicle, how well it handles and responds to driving conditions compared to its pre-accident state. If it feels the same (or better), customers are satisfied. If unfamiliar responses or nagging difference between its pre- and post-repair condition crop up, customers are either going to complain directly to your business or share negative criticism with friends and family who likely could take your services off their preferred automotive providers list. 

(Photo courtesy of GM media) Even affordable compact vehicles like the Chevrolet Cruze are equipped with sophisticated front suspensions that will need to be thoroughly examined before and after any repair. Repairs should only be conducted by sticking strictly to manufacturer instructions.

There’s an easy solution to avoiding the latter issue: Follow the factory specs. Suspensions, particularly front suspensions, are interesting creatures. They’re both rugged and sophisticated, tough and sensitive. They do a great job in handling rough road surfaces. When a jolt comes from elsewhere, particularly the kind produced to the front or side of the suspension during a collision, they are susceptible to serious damage—or at the least, damage that must be addressed during a collision repair. 

You’ll want to pay stricter attention to front suspension during pre-repair damage analysis and post work evaluations and road tests. You also may need to reevaluate how closely your shop sticks to OEM repair guidelines for each of the vehicle models you repair. 

Here’s a look at control arm and stabilizer bar replacement in a popular compact vehicle, the new Chevy Cruze, using instructions provided by GM. Use the lessons learned here, particularly the need to use specialized tools and precise calibrations, in all your suspension work. 

Note: Refer to GM recommendations for regional tools in the event you need replacements for the ones mentioned here.

Background: Keeping you in suspense

Why are front suspensions designed as they are and how does that affect how they are repaired? Funny you should ask. Understanding the answers to these questions is one of the keys to successfully performing suspension work. 

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Vehicle front suspensions essentially have two jobs: (1) isolate vehicle occupants from harsh road surfaces while (2) keeping wheels horizontal to the road to provide effective handling. Suspensions handle the first task in large part by absorbing and dissipating energy through springs, shocks and struts. The second job is performed using a series of bearings, joints and metal structures that allow the suspension to pivot and react to changing driving conditions. 

Significant here is the work of the control arms (upper and lower, left and right), which join the rest of the suspension to the vehicle frame. The control arms create an A-shaped design, with the inner part of the lower arms running from the frame where they attach, often, at two points through semi-rigid bushing. The outer part of the lower control arms link to the steering knuckle whose upper portion attaches to the strut assembly—which then connects to the vehicle body via a bearing. The steering knuckle moves up and down independent of the frame. 

(Photo courtesy of Ford media) Note that front suspension control arms run from the frame to the strut assembly.

Connecting the left and right lower control arm assemblies is the stabilizer bar (shaft). This bar dictates the amount of independent movement of the suspension when the vehicle turns (the amount of vehicle roll), which in turn defines how a vehicle handles when making turns. 

This setup permits a vehicle to both roll on its tires and alter direction while supporting the vehicle and providing a smooth, controlled and comfortable ride. This structure is standard across the automotive industry. Ride characteristics, however, can vary widely between different types and models of vehicles based upon how a particular suspension is tuned—how the parts comprising it are designed and engineered to work together to create a particular driving experience.  

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