Ground clearance, simply put, refers to how much space you have between
the lowest part of your vehicle (excluding the wheels and tyres) and the
ground. This is typically measured as under-chassis clearance and under-axle
clearance and, as can be seen in the figure below, under-axle clearance is
substantially less than under-chassis clearance. Both have implications.
Axle clearance implies how much space is between the ground and the lowest
part of your axle, usually the differential housing. Knowing where the
housing is situated (normally left or right of center) will help you avoid
damaging the differential housing by driving it into rocks. Knowing how much
axle-clearance you have will also help determine the depth of ruts your
vehicle can successfully negotiate.
|Approach, Break-Over and Departure Angles|
The approach and departure angles are the maximum angle at which a vehicle
can approach an obstacle, and depart from an obstacle, respectively. Most
vehicles have a better approach angle because the tail overhang is longer.
The ramp break-over angle is important as it determines when you're going
to beach or "belly" your vehicle. This happens when you cross over a hump
and the chassis rests on the top of the hump, leaving your front and back
wheels spinning helplessly in the air. It follows that a short-wheelbase
vehicle has a better break-over angle than a long-wheelbase vehicle.
Also remember that a tow-hook usually further reduces your departure angle.
This is a point often overlooked and can catch you out when the tow hook
digs in when reversing back down an incline. The flip-side is that if, say,
your fuel tank is situated to the rear in an exposed position, it's
preferable to damage a tow bar than a fuel tank. The same goes for bull
or bush-bars, side-bars and so forth.
|Increasing Ground Clearance|
The only way to increase ground clearance on your vehicle is to fit bigger
tyres. However, fitting really large tyres usually requires a suspension
lift, body lift, wheel spacers, or a combination of these (see below).
© 1998-2013 Michael Wittenburg and Martin Wittenburg. All rights reserved.