A Bumper That Absorbed the Hit Has Done Its Job

More than most owners expect. On a van or a truck the visible cover is usually the least structural part of it. Behind it sits an energy absorber, foam or a formed plastic crush structure designed to deform. Behind that sits a reinforcement beam, often high strength steel or aluminum, mounted to the frame or unibody through crush cans that are designed to collapse at a known load.

Then there is everything mounted through the assembly: parking sensors, a forward radar unit, a camera, fog lamps, air temperature sensors and on some vehicles a washer system. On an RV, a rear bumper may additionally carry a sewer hose storage tube, a receiver, a ladder mount or a spare tire carrier, all of which load it in ways a car bumper is never loaded.

That is why a bumper estimate is rarely one line. The cover, the absorber, the reinforcement, the brackets and the electronics are separate items with separate failure conditions, and an impact that destroyed the cover may have left everything behind it intact, or the reverse.

For plastic covers, the deciding factors are the type of plastic, the location of the damage and whether the mounting tabs survived. Thermoplastic covers can be welded and reformed; the repair is real and it holds. A cover with a tear through a mounting tab is a different story, because the tab is what holds alignment and a repaired tab tends to let the cover sag over time.

For steel bumpers, the question is whether the section is bent or kinked. A gentle bend on a heavy channel bumper can be straightened. A kink has already yielded and cracked internally at the fold, and it gets sectioned or replaced. Corrosion at the mounting points changes the answer regardless of shape.

For reinforcement beams and crush cans, replacement is the rule. Those parts are designed to deform once and they are not straightened, because a straightened crush structure no longer collapses at the load it was designed for.

Where the impact was hard enough to fold a crush can, the mounting structure behind it gets measured, which moves the conversation toward unibody straightening or frame work.

Because aim matters. A radar unit or a camera mounted in or behind a bumper is aimed relative to the vehicle's centreline and its road plane. Move the mounting by a small amount and the system is looking somewhere other than where it thinks it is, which is worse than the system being disabled.

So on any vehicle with driver assistance features, bumper work is followed by a scan and, where the systems require it, a recalibration. That work runs $275 to $1,800 across 1 to 7 hours depending on what is fitted and whether the calibration is static, dynamic or both.

Parking sensors are the quieter cost. They are cheap individually but a bumper cover carries several, they are colour matched, and a replacement cover often arrives without them. Sensor rings, brackets and the harness all get transferred or replaced, and a sensor mounted at the wrong depth in its ring reports incorrectly rather than not at all.

None of this applies to a simple steel rear bumper on a travel trailer, which is why the same operation spans such a wide band. Parts carry 100 percent markup under $100 and 35 percent over $100.

• Look at the gap between the bumper and the body panels on each side. Uneven gaps mean the mounting moved even if the cover looks fine.
• Press on the cover firmly. A cover that moves more than it should has a broken tab or a failed bracket behind it.
• Start the vehicle and check for any driver assistance warnings, and note whether parking sensors still chirp when they should.
• On an RV, check anything mounted through the bumper: the sewer tube, the receiver, the ladder mount, the spare carrier.
• Look underneath at the crush cans or brackets with a light. A visibly folded can means the impact was harder than the cover suggests.

Collision estimates are written at no charge and insurance walk ins are always welcome. Sibling work sits at fender and quarter panel repair and dent removal and repair. Bands are on the price sheet.