PBBT - Performance Based Brake Testing

Why should my fleet care about PBBTs?
By examining the measured brake forces for a vehicle, a fleet owner can help determine:

• Whether the choice of brake lining is appropriate and cost-effective for their fleet’s needs,
• The origin of uneven brake lining wear problems,
• The potential sources of tire wear problems,
• The origin an nature of air valve or other air system problems,
• The origin of stability problems during braking,
• An objective response to driver complaints about brakes,
• Whether a vehicle involved in an accident had adequate braking capability, and
• Whether his/her vehicle meets minimum brake performance standards, either self-developed and imposed, or those codified in the Federal Motor Carrier Safety Regulations (FMCSRs).

My fleet drivers have never been tested on a PBBT before, how will they know what to do?
Aside from following the instructions of the inspector, there is very little your drivers need to do other than ensuring that full air pressure is available and full brake application is made.

Are the results of a PBBT test consistent with a visual inspection of a brake system?
In general, yes, however, the two methods assess two different things: measured brake forces compared to weight with the PBBT versus the presence and appropriate functioning of physical components from the visual inspection. While a visual inspection can indicate a potential problem with a brake component, in practice the actual brake performance can never be determined by visual inspection.

To the benefit of the fleet owner, however, it has been found that the brake force measurement method is more objective and generally in favor of the fleet during a roadside inspection as well as in the maintenance shop. For example:

• A lightly laden vehicle, or a vehicle equipped with aggressive brake linings can often meet the BF./GVW requirements even though some brakes may be out of adjustment or other apparent defects may have been identified. Thus a vehicle may be considered safe to proceed in its current condition to a location where the defective components may be repairs.
• On the other hand, a vehicle’s brake system can appear defect free, yet low BF,,./GVW can still result from overload, low-friction linings, and any number of other -hidden” defects. It is important for the fleet maintenance shop to locate the cause of the low BF brakes and implement corrective measures to ensure a vehicle has adequate stopping capability and is not a potential liability to the fleet owner.

What specific test results are obtained with a PBBT and how will these benefit my fleet?
A PTIBT can provide wheel-to-wheel and axle-by-axle brake forces, which is important for:
Benchmarking – New vehicles’ brakes can be checked upon delivery to establish a baseline for future brake work or lining replacement selection.
Limiting liability – Equipment providers can ensure that the vehicles they lease or rent have adequate braking capability before they am taken by the customer. Similarly, in drayage or other drive-away operations, trailers that are picked up can be checked prior to heading out. Air system problems- PBBTs have the capability to locate and identify problems within the air system. For example: a single brake with an early apply threshold can reduce lining life by two-thirds. Correcting such a problem can save over $200 per axle per year.
Drum problems – Out-of-round and off-center drums. affecting both brake wear and braking performance, can be found with a PBBT.
Disk Brake – determines and locates warped rooters, pinpointing sticking and frozen brake calipers.
Parking brake problems – Broken or weak air chambers or spring brakes can easily be identified with a PBBT.
Cargo positioning – With additional information or estimations of weight shift during a stop, the effect of distribution as well as proper securement of cargo during a dynamic stop can be assessed.

What other benefits are there for my fleet?
Potential savings on insurance – Work with your insurer to determine whether your premiums can be lowered through the use of a PBBT.
Lower fuel costs – By identifying dragging brakes or bad bearings that result in extra fuel consumption.
Cost effective testing – Testing with a PBBT can lower repair costs along with labor costs.
Safety and Performance – Stopping distance. for which maximum braking capability is but one factor, can be improved through improved brake balance and increased overall maximum brake strength.

In my maintenance shop, can’t the same information be obtained from a complete brake inspection?
While some of the information available from a PBBT can be determined from a physical brake inspection, additional complementary information is obtained. In particular, no known visual inspection method can determine whether a given brake has adequate braking forces. Visual inspections cm infer a potential lack of performance if certain components are missing, damaged, or are out of adjustment. However, the actual brake performance depends not only on all components being present and in proper mechanical order, but particularly on the friction forces generated at the drum/block (or disk/pad) interface. In the case of some non-OEM after-market linings, contaminated or glazed linings and pressure restrictions in air lines, the braking performance can be dramatically degraded despite the proper appearance of all mechanical components. The use of both complementary techniques is ideal for the maintenance shop.

Can’t I get the same information from a stopping distance test performed in my yard?
Not exactly. While stopping tests are the oldest quantitative method of determining overall vehicle performance, they provide limited information. The detailed brake force and balance information which helps a flee keep its maintenance costs down are not available from a stopping distance test. Nor is any of the diagnostic air systems information that can be determined with some PBBTs available from a stopping test.