Truck 6×4: air suspension or leaf springs

A 6×4 tractor unit has three axles, two of which are rear drive axles. This wheel formula better realizes traction and distributes load compared to 4×2, but by itself doesn't make the vehicle suitable for any off-road terrain. The type of rear trailer, reducers, differential locks, gear ratio, tyres, and ground clearance also matter. More on the differences — in the comparison of 4×2, 6×2, and 6×4 tractor units.

A separate consideration when choosing a 6×4 tractor unit is whether the rear drive trailer has pneumatic or leaf spring suspension. We'll examine their advantages, drawbacks, and areas of application using two Volvo FH 6×4 from the TIRkomis lot in Rivne as examples.

Two Volvo FH 6×4 on the TIRkomis lot

The older and more powerful Volvo FH16.610 costs less than the FH13.500, so these tractor units should be compared primarily based on future working conditions. In addition to the vehicles on the lot in Rivne, the TIRkomis catalogue has similar 6×4 tractor units with online listings that remain with their owners and are available for inspection by prior arrangement.

Which jobs these tractor units are suited for

Pneumatic 6×4 does not mean a weak chassis. Volvo provides for 6×4 pneumatic and spring axles with different permissible loads. Therefore, the choice cannot be made solely by suspension type: you need to determine the factory axle code, reducers and permissible load by VIN.

What to check before buying

On the FH13.500, cracks in airbags, skewed chassis, one side dropping after stopping, and frequent compressor operation may indicate leaks. On the FH16.610, displaced leaves, axle misalignment or uneven tire wear may indicate faulty balancers, bushings or compromised geometry.

Hydraulics are checked with the PTO engaged and the pump under load. More details in the article about tractor with hydraulics. Volvo Tech Tool diagnostics should show engine hours, EBS/ECAS faults and engine and gearbox parameters. The practical procedure is outlined in the article on checking a truck in 30 minutes. Power of 500 or 610 hp does not determine the permissible vehicle combination mass. It is confirmed by the factory card, axle and gearbox codes, gear ratios and registration documents.

Should you convert pneumatic to spring

Converting FH13.500 may require different brackets, balancers, reactive rods, ECAS and pneumatic line modifications, fifth wheel height adjustment, driveshaft angles and weight distribution checks. Errors cause axle misalignment, tire wear, transmission vibrations and frame cracks.

If design parameters or weight distribution change, approval and compliance assessment under the GSC MIA procedure and CMU resolution No. 607 are required. The cost of work and downtime should be compared with buying a factory spring tractor unit.

Which 6×4 tractor unit to choose

The FH16.610 on leaf springs is better suited for heavy trailers, tipper semi-trailers and work on construction sites, damaged access roads or in the field. The permissible vehicle combination mass and transmission suitability must be confirmed by documents.

The FH13.500 on air suspension is more appropriate for haulage along established routes, where ride smoothness, automatic transmission and seat height adjustment are important. Access to a compacted construction site is possible, but the air suspension condition and ground clearance should be checked before purchase.

Both tractor units are available at the TIRkomis yard in Rivne: you can inspect them, compare and diagnose them. Financing options for vehicles are also available.

The owner of commercial vehicles can place them on commission. Parking space and advertising are free until sale, and a $500 commission is paid after the contract is concluded. To search or get an appraisal, call: +380 97 102 65 55. New listings — in the TIRkomis Telegram channel.