Getting Bit by Bumpers

It happens every day -- drivers and their cars get into minor fender-benders in parking lots. Because the cars are traveling so slow no one is hurt, but there still is a big element of pain -- in the wallet. A simple six-miles-per-hour crash in a Mercedes-Benz C-Class was recently estimated to cost more than $5,000 to fix, according to the Insurance Institute for Highway Safety. And that is just one example of the fact that bumpers on many luxury cars don't seem to be capable of doing what they are supposed to do: protect the rest of the vehicle from damage in slow-speed crashes.

In the Mercedes-Benz C-Class cited above, its front bumper is mounted so low that it under-rode the barrier in the Institute's front full-width test, so the bumper itself escaped virtually unscathed. A little touch-up paint was all that was needed to repair the plastic bumper cover. The bad news is what absorbed the energy of the impact was the C-Class's grille, hood, radiator, headlight and air conditioning condenser, all of which were damaged. This is how the repair costs escalated to more than $5,000, the highest total sustained by any of the 11 luxury cars in any single test.

"This is exactly what we don't want to see," said IIHS senior vice president Joe Nolan. "The car body took the hit."

To assess and compare bumper performance in low-speed impacts, IIHS has begun conducting a series of four low-speed tests -- full front and rear into a barrier designed to mimic the front or back bumper on another vehicle plus front and rear corner impacts. The full-width impacts are conducted at six mph while the more demanding corner impacts are run at three mph. These tests replace the five-mph flat-barrier and pole tests the Institute conducted for decades to assess bumper performance. The new tests, which reflect years of development, are said to replicate more closely the damage patterns in today's low-speed collisions between vehicles. The first set of results of the Institute's new tests involved inexpensive and moderately priced midsize cars, which sustained up to about $9,000 damage in the four tests.

"Luxury cars don't perform any better than cheaper cars," Nolan pointed out. "There's nothing luxurious about shelling out thousands of dollars to fix damage from a bump at a speed about like a brisk walk."

While the C-Class fared the worst in one individual test, the Infiniti G35 was the worst performer in the four tests combined. It sustained almost $14,000 damage in the total series. The Saab 9-3 was the best, sustaining $5,243 damage. Only three cars -- Saab 9-3, Audi A4 and Lincoln MKZ -- sustained less than $6,000 damage, while four -- Lexus ES, Mercedes-Benz C-Class, Acura TL and Infiniti G35 -- would cost more than $10,000 to fix.

This is especially frustrating for the insurance industry and those of us who pay insurance premiums, because these low-speed, non-injury crashes cost millions of dollars each year. The purpose of a bumper is to absorb the energy of a low-speed collision before it damages expensive-to-repair parts like fenders and hoods. But there are multiple problems, the first of which is that the bumpers on colliding vehicles often don't line up so they don't engage in a collision to begin with. And even some that do line up don't stay engaged during an impact. Their aerodynamic styling may allow them to slide under the bumpers of the vehicles they strike. This means they can't do the job of energy absorption.

Another problem is that the bars underneath bumper covers, which are supposed to do the main work of absorbing crash energy, often aren't up to it. They may not be big enough to provide much protection from damage, especially if they don't extend to vehicle corners, or they may be too flimsy to absorb much energy.

High repair costs after minor bumps also reflect the high price of replacement parts to fix the damage. This is especially true of luxury cars, which are expensive not only to purchase, but also to repair.

Sadly, there doesn't seem to be much impetus among car manufacturers to do anything about the issue. But good design can make a difference. For example, the Audi A4 was the best performer among the luxury cars in both front and rear full-width tests. Equipped with components that work like shock absorbers to dissipate crash energy before it can damage the car body, the A4 sustained less than $1,000 damage in each test.

"It isn't coincidental that the A4 is the only luxury car among the 11 we tested with this kind of absorbers, which usually outperform other methods of managing the energy of crashes," Nolan said. "If the A4 had longer bumpers for protection in corner impacts, it probably would have been the best performer among this lot of cars instead of second to the Saab 9-3. A bonus of stroking energy absorbers is that they don't have to be replaced after every impact. They can absorb energy again in subsequent collisions."

Driving Today Contributing Editor Tom Ripley writes about the auto industry and the human condition from his home in Villeperce, France.