The clutch is how the engine transmits its power through the gearbox and to the wheels. In its default state, it is engaged – it is connecting the gearbox to the motor. Pushing the clutch pedal (on a car or lorry), or pulling the clutch lever (on a motorbike) disengages the clutch and enables you to change gear.
A clutch should last between 50,000 to 100,000 miles, but it depends on:
- The driving you do – lots of rush hour stops and starts wears it out, as will track days and hard driving
- Towing – when starting from a standstill with a heavy load, the clutch is under much more pressure
- Driving technique – slipping or riding the clutch rather than apply the handbrake, or driving with your foot resting on the clutch will wear it out much quicker
- The type of clutch – heavy duty clutches will last longer
- The type of vehicle – high performance vehicles place more demands on a clutch. A hypercar might need a new clutch every 20,000 miles, whereas you might get 120,000 miles out of a low-powered Japanese hatchback.
The clutch can fail in three main ways:
- Clutch cable snaps
- Hydraulic system has a leak
- Clutch wears out
A clutch cable is used on motorbikes and cheaper small cars. If it snaps, the clutch will be permanently engaged: pushing the clutch pedal or pulling the clutch lever won’t lift the pressure plate from the flywheel. The pedal will go to the floor or the lever will be able to be pulled in easily. It will be difficult to change gears without matching the revs to the road speed, and it will be almost impossible to start a car or motorbike without doing a jump start – the gears will graunch. If this happens while you are in-gear, you can continue to drive until you find a safe place to stop.
If the hydraulic system has a leak, the initial indication might be that the clutch pedal feels different. It might have a vibration or might go to the floor much more easily. Eventually, the gear changes will become difficult and notchy, and finally you won’t be able to change gear. If this happens (and it can happen suddenly if there’s a catastrophic leak in the hydraulic fluid), then you can continue driving until you can find a safe place, but bear in mind you won’t be able to start again if you stop the vehicle.
The clutch wearing out will give you potentially months of warning. The first sign will be that as you use full throttle (e.g. to overtake another car or to pull away quickly from a standstill), the engine revs rise, but you don’t experience as much acceleration as you would expect. This is the clutch slipping as the friction material wears out. You can continue to use it, but it will get worse and worse until eventually it will slip even if you simply try to drive gently uphill.
Therefore, you can continue to drive the vehicle after the clutch has failed, but if it’s a catastrophic failure, then you’ll eventually need to pull over somewhere safe and then get the vehicle to a mechanic.