Dimensions and weight

Unladen weight (also called kerb weight) is the weight of the machine without payload, operator, fuel or mounted implements - it describes just the machine itself, as it leaves the factory or stands in the yard. Gross vehicle weight, by contrast, is the upper limit set by the manufacturer up to which the machine may be driven loaded, fuelled and fitted with implements or trailers without overloading its design (axles, brakes, tyres). The difference between the two figures is the maximum permitted payload - a practically important number for front-loader attachments, ballast or transported goods. Exceeding the gross vehicle weight risks not only increased wear on axles and brakes but, depending on the country, also insurance and registration consequences. Both figures are normally shown on the machine's nameplate and should not be confused with each other when comparing listings.

Wheelbase is the horizontal distance between the front and rear axle (or between the first and last axle where there are more than two). A longer wheelbase usually improves stability at higher speed and on uneven ground, while a shorter wheelbase allows a tighter turning circle and more manoeuvrability in confined spaces, such as a barn or between rows of trees. On tractors with mounted implements, wheelbase also affects weight distribution, especially with heavy front- or rear-mounted equipment. For road transport work, a longer wheelbase is usually an advantage; for work involving frequent manoeuvring or tight turns, a shorter one tends to be better. When comparing two machines of similar power, wheelbase can therefore hint at what main use the machine was originally designed for.

Ground clearance is the smallest distance between the lowest fixed point of a machine (usually the axle or gearbox housing) and the ground. It determines what obstacles - furrows, stones, tall rows of plants - a machine can cross without touching down or damaging components. For row crops such as maize, sugar beet or vines, adequate ground clearance is essential so the plants are not damaged when driven over; for construction machinery on uneven terrain it helps avoid damage to the vehicle from the ground itself. Greater ground clearance usually comes with a higher centre of gravity, which tends to worsen tip-over stability on slopes - so buyers face a trade-off depending on the main area of use. In a technical comparison it is worth looking at ground clearance together with the intended crop or terrain, rather than reading it in isolation as "more is always better."

Power-to-weight ratio relates engine power to the weight of the machine, usually expressed as kilowatts per tonne (kW/t) - it describes how much drive power is available for every tonne of machine weight. A higher power-to-weight ratio generally points to brisker acceleration and more dynamic handling, while a lower ratio tends to indicate a machine built for pulling power and stability rather than speed. For the register's ranking, the power-to-weight ratio is only calculated when both power and weight are documented figures and the kilowatt and horsepower figures do not contradict each other - without both values the number would be pure speculation. It does not replace a test drive and says nothing about the reliability, fuel consumption or condition of a specific unit; it only places a model within its group on a purely arithmetic basis. Between very different machine types (say, a tractor and an excavator), a direct comparison of power-to-weight ratio is also of limited use, since they perform entirely different kinds of work.