Glossary
Glossary
Twelve terms that come up in every second conversation at the ask desk, written out the way we would explain them across the bench. These are the ones that cost people money when they are misunderstood.
Twelve terms, in the order they come up
- 01Kerb weight
- The mass of the car with all its fluids, a full tank of fuel and no people or luggage in it. It is the baseline for everything else: subtract it from gross vehicle mass and what remains is your payload. Watch for figures quoted without fuel, or for a base-model kerb weight printed in a brochure for a car that is actually the heavier all-wheel-drive version. On the plains, a heavier car usually rides better over patched tar and costs you more in tyres.
- 02Payload and gross vehicle mass
- Gross vehicle mass is the heaviest the loaded car may legally be. Payload is that figure minus kerb weight, and it has to cover every person, every bag, the roof box and the tow ball download. Seven adults at an average of 78 kg is 546 kg before luggage, so a seven-seater with a 580 kg payload is a four-seater with ambitions. The plate on the door pillar carries the real numbers.
- 03Overrun
- What the engine and gearbox do when you lift off the accelerator. On overrun a car may coast freely, or it may hold a low gear and brake with the engine, or it may shuffle down two gears looking for engine braking you did not ask for. The last behaviour is pleasant on a mountain pass and tiring on 450 km of flat N1, which is why we note it for every automatic we drive.
- 04Torque converter
- The fluid coupling that lets a conventional automatic sit still in gear without a clutch pedal. It is the reason a torque-converter automatic creeps smoothly in a Loch Logan parkade and the reason it slips slightly before it locks up. It is also the most durable automatic type on gravel and in stop-start traffic, which is why we are relaxed about one at 150 000 km and cautious about some alternatives.
- 05Continuously variable transmission
- A gearbox with a belt or chain running between two cones instead of fixed gears, so engine speed and road speed move independently. It is efficient and smooth, and it produces the rising drone people dislike on an N1 overtake. The thing to check is the fluid specification and interval, because the fluid is particular and expensive, and a missed change is how these gearboxes die at an indicative R60 000 or more.
- 06Run-flat tyre
- A tyre with a sidewall stiff enough to carry the car for about 80 km at 80 km/h with no air in it, which is why cars fitted with them often have no spare. Two consequences for Free State driving: the ride is firmer because that sidewall cannot absorb a gravel stone edge, and a puncture outside Petrusburg means a replacement tyre rather than a repair, at an indicative R3 200 to R6 500 each. Ask what the car carries before you need to know.
- 07Load index and speed rating
- The number and letter at the end of a tyre size, as in 225/45 R18 95W. The number is the maximum mass that tyre may carry, the letter the maximum speed at which it may carry it. Fitting a lower load index than the manufacturer specified is the commonest quiet mistake in tyre shops, and it matters most on a fully loaded seven-seater on a hot afternoon, which is exactly when a sidewall fails.
- 08Severe-duty service schedule
- The shorter service interval most manufacturers publish for dusty roads, short trips, heavy loads and high altitude. Almost every car in the Free State qualifies on at least two counts, and almost nobody is told. Oil and filters at 10 000 km instead of 15 000, cabin filter three times a year, and gearbox oil earlier than the sticker says. It costs an indicative R3 000 a year more and it is the cheapest reliability you will ever buy.
- 09Service plan and maintenance plan
- Two very different things sold in the same breath. A service plan covers scheduled servicing: oil, filters, labour. A maintenance plan covers those plus the parts that wear out, including brake pads, discs, wiper blades and often a clutch. The gap between them over six years and 120 000 km is an indicative R30 000, and it is the single most useful question to ask on a showroom floor.
- 10Laden ride height
- How far the car settles when you put the load in it, measured from wheel centre to arch lip before and after. A 20 to 30 mm drop at the rear is normal and healthy. Much more than that means the springs are soft for the load and the remaining bump travel is thin, which on a corrugated district road arrives as a bang through the floor and, eventually, as a broken rear shock absorber.
- 11Diesel particulate filter regeneration
- A diesel's filter burns off collected soot periodically, and that burn needs a sustained run at speed. A diesel used for 6 km school trips through Universitas never completes one, blocks, and presents a bill at an indicative R25 000 to R40 000. If your driving is mostly town with an N1 run twice a month, a petrol engine is the sensible choice and the fuel saving on paper will not cover one blocked filter.
- 12Driver-aid calibration
- Lane-keeping, adaptive cruise and automatic braking depend on a camera behind the windscreen and radar behind the bumper, both of which need recalibrating after a windscreen replacement or a bumper repair. On the plains, where a stone chip is a seasonal event, that is an indicative R2 500 to R7 000 you must add to every windscreen. Ask whether your local workshop can calibrate, because sending a car to Gauteng for it is a two-day exercise.