So what are Portal Axles?
Portal axles (or portal gear) are an offroad technology where the axle tube is above the center of the wheel hub and where there is a reduction gearbox built within the hub. Portals are also referred to as drop gears or drop gear sets, dependent on where in the world you are.
The main advantage is a greater ground clearance, with the added benefit of the hub gears allowing the axle half-shafts to drive the same power but at a reduced torque at higher shaft speed. Thus reducing load on the crown-wheel and differential.
Bolt-on Portal Axles by the likes of Tibus off road engineering, are portals that can be attached to existing axles as an after market add on.
Portals are developed to maintain the rotational direction of the original axle, which is achieved by using the 4 gears inside the drop box. Another advantage of 4 gears is the optimal distribution of torque on to the extra gears hence a higher torque can be transmitted inside the drop box and temperature control is improved.
By installing Tibus axles, the vehicle height is increased by 5″ (125mm) or 4″ (100mm) dependant on specification ordered.
This height increase allows you to mount larger tyres without changing your suspension or even cutting your bodywork. Axle and steering geometry stays untouched saving costs on castor correction and propshaft alignments. The reduction in gear ratio of the bolt-on portals 1,6:1 is equivalent to a 60% load reduction of the axle and drive-line, or so to speak, a 60% improvement of axle strength.
As the whole drive ratio is altered by the factor of 1,6, it´s now possible to use larger tyres without changing differential ratios.
To achieve this addition of ground clearance without portals you would have to mount 10″ bigger tyres.
This would mean more than cutting into your car´s body panels as most axles would not have the strength to handle these tire sizes off road.
Portals are currently available in two versions for the likes of the Land Rover Defender, Mercedes G Wagen and Jeeps with beam axles.
1,6:1 for heavy offroad use
1,16:1 for daily use, travel and expedition
Portal drop boxes can be fitted to independent suspension vehicles and the opposite way around for vehicles requiring low floors, such as disabled access buses where the axle is below the wheel center point.
Check out this animated video of a Portal Axle build …
For Portal Axles go to Tibus Off Road Engineering