Engine braking advance gives 4WD quads the edge on hills
Engine braking advance gives 4WD quads the edge on hills
By Andy Collings
BETTER downhill engine braking is one of several new features to be found on the new four-wheel drive Polaris Magnum HDS 325 and HDS 500 ATVs imported by Bicester, Oxon-based EP Barrus.
The improved braking effect is a result of Polaris developing a viscous coupling in the front axle, which now offers permanent 4WD and maintains a positive engagement to the front axle when the ATV starts to descend hills.
"Customers were complaining of excessive brake wear," says EP Barruss vehicle division service manager Roger Sucking. "Previous Polaris 4WD systems used a selectable system which relied on a Hilliard clutch system with electromagnetic engagement – but it was a system that could overrun when the ATVs went downhill, losing engine braking on the front axle."
"With such a system, effective downhill engine braking could only be achieved on the rear axle," he says. "It was fine with just the ATV, but for those towing a loaded trailer, it put additional strain on the all-round disc brake system and led to excessive brake pad wear."
Barrus claims the viscous device eliminates the need for a front differential and it provides a permanent mechanical link between the engine and front axle. On slippery surfaces, the coupling can monitor the speed of the two front wheels in relationship to each other and lock progressively up to 100%, to provide true 4WD when the going gets tough.
"It is a mechanical system that uses a combination of fluids and silicon – like the centre differential on some 4×4 cars – to provide reliable traction without affecting the turning circle, reducing tyre life or inducing excessive torque steer," says Mr Sucking.
Other improvements to Polaris Magnum ATVs include the use of CV joints on the front axle, braided steel hoses for brake lines to provide a more positive feel at the brake levers, wider mudguards and larger diameter front brakes.
Polaris 2001 models also get a silver/grey livery and prices are said to be unchanged. *