This is the final article in our series, discussing possible issues with dynamometer testing. We provide you with possible causes as well as suggestions to repair them.

The Problem: Dynamometer Testing of Vehicles with Air Suspension

Here are possible causes and suggestions:

During dynamometer or 'roller' testing of vehicles fitted with air suspension, vehicles are often incorrectly failed on the grounds of poor braking performance. The wrong results are often obtained due to the physical properties of air suspension affecting the readings.

With air suspension vehicles with more than one axle, as the wheels on the rollers brake, the axle lifts, compressing the suspension bags. The roller tester equipment will read that the brakes on that axle are not braking sufficiently. When testing vehicles fitted with air suspension, the axle being tested should be "blocked" or prevented from lifting.  

Some test stations are now fitted with chains or straps with hydraulic rams to anchor the axle down during testing. If this facility is not available, it is advised that the simple procedure below be followed to ensure that more accurate braking test results will be obtained.

This handy tip will help you handle dynamometer testing of your airbrake system. If you are in need of professional help, JMR specialises in brake systems and parts and we uphold the highest standards in workmanship. Please contact us today for all your brake system needs.

We continue our series of articles on possible issues with your air brake system. We have two more popular problems and provide you with possible causes as well as suggestions to repair them.

The Problem: Trailer Axle Data Plates

Here are possible causes and suggestions:

According to the Department of Trade and Industry's National Regulator for Compulsory Specifications of Act 5 of 2008, which also incorporates all the requirements of the ECE R13 regulations, the following details are stated on section 4.4. of the document and read as listed below;                                       

"Each axle on a trailer shall be provided with information applicable to the brake design, the particulars of which shall be permanently and legibly imprinted or stamped either on a data plate permanently affixed in a conspicuous position adjacent to the axle or on the plates as required by SABS ECE R13, as follows:                                                                                                                                                                         

1. The axle make and serial number;                                
2. The brake chamber size and the brake lever length;                                               
3. The maximum tyre size; and                                                                                                                                                       
4. Brake lining material type and grade 4.2.3 Axle data"     

In addition to this information on a data plate affixed to the axle, the following information is also required: 

1. The load capacity of the axle: and                                                                                                                                            
2. The maximum rolling radius of the tyre.                                    

Note: Although these are standard requirements in the SABS ECE R13 regulations, I have still to see any trailer axles with all of this information affixed to them.                                                                                                                            

The Problem: Truck Brake Conversions

Here are possible causes and suggestions:

A rigid truck with existing EBS brake system, cannot be converted to a truck tractor by simply installing a standard trailer control valve. Due to the incompatibility between the components, i.e. using an electrical brake system (EBS) with a normal pneumatic trailer control valve, the towing vehicle brake system will not function correctly and cannot efficiently control the trailer brake system. Also, this type of conversion is not approved by the OEM truck manufacturers.

If the truck is not fitted with an EBS brake system and is either fitted with a standard ABS brake system or is fitted with a standard brake system, then it is acceptable to install a standard trailer control valve, however, when doing this conversion it is also necessary to make sure that the hand brake valve that is fitted to the truck is a 3-port unit, (in other words one supply port and two delivery ports, not forgetting the exhaust port). The extra delivery port is necessary to meet the requirements of the SABS ECE R13 regulations and is there to operate the trailer control valve independently of the spring brakes.                          

Standard trucks, because they are not originally equipped for towing trailers, only need the hand brake valve to apply and release the spring brake boosters, but if converted to tow trailers the extra port on the hand brake valve is necessary to comply with the "test position" application of the regulations.                                

This handy tips will help you sort out your faulty air brake system. If you need professional help, JMR specialises in brake systems and parts and we uphold the highest standards in workmanship. Please contact us today for all your brake system needs.

This is the next article in our series and we explore an important aspect of your air brake issues – your trailer data plates. We provide you with possible causes as well as suggestions to repair them.

The Problem: Trailer Data Plates

Here is a possible cause and suggestions:

1. According to the ECE R13 brake regulations all trailers, built after February 2004, have to be fitted with a data plate showing all the necessary information to assist the proper future maintenance of the vehicle. In order for the trailer to pass the Homologation test, the technical specifications of all the valves and equipment, used to calculate the final brake system performance, were taken into account. The data plate will therefore include the part number of the Load Sensing valve used, so as to make sure that if the valve is ever replaced, it is replaced with a valve that has the exact performance characteristics as the one whose part number, is stated. Failing to do this could make the brake system non-compliant and could result in serious brake performance problems. The data plate must also give the number and size of all the brake boosters used on the trailer and also the slack adjuster lever length information, for each individual axle. In addition, the data plate must give the output air pressure to the booster service brakes, in relation to an input pressure, in the laden and unladen load conditions. (A typical example is shown below).    

This is a handy tip to help you sort out your faulty air brake system. If you need professional help, JMR specialises in brake systems and parts and we uphold the highest standards in workmanship. Please contact us today for all your brake system needs.