The term “bearing test” can refer to two things: a car engineering test where a ball bearing is rolled along the car’s design, and a road surface penetration test called the California Bearing Ratio (CBR) test. The car test was first used in a 1992 ad campaign for the Lexus ES 300 and later repeated by Nissan. The CBR test determines the suitability of road subgrades and foundation courses by measuring the bearing capacity of soil samples.
The term bearing test can refer to two separate things. The first use of the term is often associated with Lexus and Nissan automotive engineering. The other refers to a road surface penetration test also known as a California Bearing Ratio (CBR) test.
When associated with automotive engineering, the term bearing test dates back to a 1992 ad campaign for the Lexus ES 300. In this TV ad, the Lexus ES 300 was mounted on a platform that allowed it to rotate in different axes . The advertisement described the ball bearing test as an engineering test of the car’s design.
In the Lexus bearing test, a silver ball bearing was placed on the hood seam of the car and released. It began to descend along the hood seam, and as the car was rotated on the platform, it continued its journey along various parts of the car’s design. The purpose of the test was to show the precision engineering that allowed the ball bearing to travel unhindered.
This version of the bearing test was later repeated by Nissan with the release of the 1993 Nissan Altima. The Nissan commercial paid homage to Lexus by acknowledging that the idea for the test came from Lexus advertising in their advertising campaign. However, the Nissan publicity team did include a subtle joke against the Lexus, noting that the 1993 Nissan Altima was significantly less expensive than that year’s Lexus models.
When associated with road surface construction, the term bearing test usually refers to the California bearing report test. This test is used to determine the suitability of road subgrades and foundation courses by ascertaining the bearing capacity of the soil sample. Higher CBR values are indicative of harder surfaces suitable for unimproved roads and airstrips. Lower CBR ratings demonstrate soft surfaces that are unsafe for road construction. The test method was first developed by the California Department of Transportation before World War II.
Bearing ratio testing is conducted in the laboratory or in the field. The equipment for this procedure consists of a standard size plunger and a device for measuring the pressure exerted on the plunger. The plunger is forced into a soil sample and the pressure required to penetrate the soil is recorded. This measurement is then divided by the pressure required to duplicate the test on a standard crushed stone material of 100% CBR. The resulting number is then given as a percentage of CBR.
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