Vehicle Conversions

Truck Mid Axle Installations

Axles mounted in front of the drive axle to form a close-coupled bogie are termed ‘Mid Axles’ or ‘Pushers’. They have a ‘Drop Centre’ in the tube to allow clearance to the propeller shaft. Granning offer a wide range of suspensions and axles for this purpose in order to ensure that the additional equipment compliments the original vehicle specification.

Granning can supply Disc or Drum braked axles to carry tyre sizes from 17.5″ to 22.5″ are available for twin wheel, single offset wheel and single centre knave configuration. The RM (Retro Mid) series of suspensions offers compact space saving design with twin lift assemblies enclosed for maximum protection. These suspensions are compact in order to retain maximum fuel capacity, and are durable and hard working. The suspension operating pressure can be adjusted by clever installation to match that of the drive axle thus often eliminating the necessity to fit reduction valves to perform this task. Popular applications are Tractor unit mid axle taking the tractor from an 18000kg gross vehicle weight to a 23000kg tractor that has the three axle configuration required to operate at 44000kg gross train weight.

The axle is able to lifted when the vehicle is unladen thus saving tyre wear and allowing the drive axle to carry more mass giving greater traction.  A number of Car Transporter Drawbars employ Granning 600 series mid axles in order to fit space saving 17.5″ tyres which don’t encroach into the bodywork yet carry sufficient load to prevent the front axle overloading.  This arrangement is also employed on many municipal and refuse vehicles, which again have restrictive space for axle mounting owing to bodywork, lifts and cranes etc.

Mid axle showing Drop Centre Tube to avoid prop shaft

Mid axle installation, axle lifted.

Tractor mini disc braked axle

Rigid Narrow Track Mid Axle for municiple use.

Truck Tag Axle Installations

An additional axle mounted behind the existing vehicle Drive axle to form a close-coupled bogie is termed a Tag or Trailing Axle.

Granning offer a wide range of suspensions and axles for this purpose in order to ensure that the additional equipment compliments the original vehicle specification.

Disc and Drum brake axles to carry tyre sizes from 17.5″ to 22.5″ are available for twin wheel and for single centre knave and offset wheel configurations.

Our RT (Retro Tag) range of suspensions are usually employed for this style of installation, they offer a practical solution to the vehicle converter for mounting the axle in this position but with twin lift built in saving assembly time and expense.  Twin wheeled installations usually form an equally plated bogie where the mass on the Tag axle is the same as that carried by the Drive Axle, Wide track single wheeled configurations are available that offer maximum stability when an asymmetric bogie is required by the operator. These suspensions offer high stability and durability and variety of lifting methods are available should the standard twin lift be unsuitable for your application.

Single Wheel Tag Axle

Twin Wheel Tag Axle

Drive Axle Air Suspensions

Granning have developed many drive axle air suspensions for different vehicles to replace the original mechanically sprung suspension.  Air suspension is ‘Road Friendly’ and Load Friendly giving greater protection to loads and causing less damage to the road surface. Suspensions have been fitted to most sizes of vehicles from 3500kg gross mass to 18,000kg.  Air suspension offers constant ride height, superior ride and handling and can be utilised to raise and lower the chassis to assist loading and unloading, ECAS (Electronically Controlled Air Suspension) can be employed to control this. Giving that greater protection to the load, ‘Road Friendly’ suspension is mandatory in legislation to operate vehicles at particular capacities.

Our drive air suspensions come in two main types, PDL (Primary Drive – Light) and PDH (Primary Drive – Heavy).  The PDH suspension can be plated up to 11,500kg, and will fit the majority of 17,000kg & 18,000kg trucks and tractor units.

Our large range of PDL kits are designed for vehicles with a drive axle mass of 1200kg to 6000kg.

Drive axle air suspension

Electronic braking conversions

Granning have always been at the forefront of Type Approval for additional axle conversions to Type Approved Vehicles.

Since the introduction of Electronic Brake control on commercial vehicle chassis equipped with disc brakes, our Engineering team have been working closely with the vehicle manufacturers and the UK Driver and Vehicle Standards Agency (DVSA) – Department for Transport to integrate additional axle brakes into the original system.

A declaration from the vehicle manufacturer has to be presented to the DVSA, to satisfy them that the conversion would not adversely effect the operation of the braking system before they will issue plates for a vehicle.

Recently vehicle manufacturers have been allowing less conversion options for their newer chassis due to the complexity of the EBS systems and its integration into the whole truck electronics.

Granning has developed a solution in conjunction with the braking system manufacturers Wabco and Knorr-Bremse, and under the oversight of the Department for Transport and DVSA, to fit an independent EBS system for the additional axle. Allowing the possibility of converting any EBS truck without the need to involve the chassis manufacturer. This system was fully tested and approved at the MIRA testing grounds, to satisfy all requirements set by DVSA and DfT with regard to EBS conversions.

Independent EBS system fitted to truck additional axle