how long to let down a car tyre

Letting down a car tyre is a job measured in coffee sips, not hours. Dropping from about 250 kPa to 125 kPa with a fast deflator (core-out type) usually takes 20–45 seconds per tyre. Using a simple bleed tool or gauge, allow roughly 1–3 minutes; jabbing the valve with a key is the slow, numb-finger method and can take 2–5 minutes. Going all the way to “flat” can take 5+ minutes and is only for emergencies, not driving. Big 4x4 tyres and cold mornings slow things down; small hatch tyres are quicker. Stop at your target pressure, double-check with a gauge, and never drive at road speeds on anything under about 125 kPa—reinflate before hitting the bitumen.