A tyre bulge, a sinking brake pedal and a spare of the wrong size
It is 5:45 pm on a Friday and you plan to drive 45 km along the East Bank Demerara to visit family, returning after dark with four adults and luggage in the car. Your checks turn up the following: the front near-side tyre has a thumb-sized bulge in the sidewall; the spare in the boot is a different size and its tread measures about 3 mm against 6 mm on the road tyres; when you hold the brake pedal down at a standstill it sinks slowly almost to the floor; the near-side headlamp is out although main beam works; one rear brake light works. The fuel is fine and the wipers are new.
1. Rank these faults by the danger they create on this particular trip and explain what each one indicates.
Read the worked answer
1. The sinking brake pedal - most dangerous. A pedal that creeps to the floor under steady pressure points to a hydraulic fault: a leaking master cylinder, a leaking wheel cylinder or a line losing fluid. Brakes that fail progressively at speed, on a loaded car, at night, are the worst fault on the list. It means the car is not roadworthy and should not make the trip at all.
2. The sidewall bulge. A bulge means the internal cords are damaged. It is not a cosmetic flaw - it can let go without warning, typically at speed or over a pothole, with a full load. In a front tyre it also takes away steering control.
3. The headlamp out, with a night return. Only one headlamp means other drivers misjudge your width and distance, and your own view of the left edge is reduced.
4. The brake light. A following driver gets no warning that you are slowing - dangerous, cheap to fix.
5. The mismatched spare. A latent problem, relevant only if you fit it - but that becomes very relevant if the bulging tyre fails en route.
2. Could the spare be used to get the car mobile? Set out the limits you would put on it and the reasoning behind them.
Read the worked answer
A different-sized spare is a limp-home device, not a replacement tyre.
Limits I would set:
- Fit it only to a non-driven wheel if the handbook says so, and only to reach the nearest garage - a short distance at low speed, well under the normal limit.
- No motorway-style running, no sustained highway speed, no towing, no heavy load.
- Expect altered handling and braking balance: one corner with a different diameter and 3 mm of tread against 6 mm will pull under braking and can confuse stability and ABS systems.
- Re-check the wheel nuts after a short distance, and get the proper tyre fitted before any further journey.
Why the limits matter here: the planned trip is 45 km each way at highway speed, at night, with four adults and luggage. That is the exact combination - speed, load, darkness - in which an odd-sized spare is most likely to bite. So the spare gets you to a tyre shop in daylight, and nothing more. It is not a way to rescue tonight's plan.
3. State your decision for tonight and the order in which you would put the car right.
Read the worked answer
Decision: the car does not go tonight. The brake fault alone settles it - a hydraulic problem that worsens with heat and use is exactly what you must not test on a 90 km round trip with a full load. The bulge and the dead headlamp reinforce the same answer, and the night return removes any margin for error.
Order of work:
- Brakes - inspected by a competent mechanic, leak found and repaired, fluid topped and bled, pedal firm under sustained pressure before anything else.
- Tyres - replace the bulging tyre; check the others for age, pressure and tread.
- Lights - headlamp and brake light, then a full walk-round check of all lamps.
- Spare - get a correct-size spare, properly inflated, and check the jack and brace are present and usable.
Then: a short daytime test drive before committing to a long trip. Arrange alternative transport tonight - borrowed car, bus, or postpone - rather than trading safety for convenience.