The Tread Ladder

Tread is the patterned rubber touching the road; its job in the dry is modest and in the wet is everything — the grooves evacuate water so rubber meets road.

State	Depth	Meaning
New tyre	8-9mm	Full wet performance
Worse wet grip begins	3-4mm	Wet stopping measurably degraded; aquaplaning threshold dropping
Legal minimun	1.6mm	Legal - poor in the rain

The ladder's lesson is the gap between the middle and bottom rows: a tyre spends a long portion of its legal life performing badly in the wet. "Legal" is a prosecution threshold, not an engineering endorsement — plan replacements around the 3 mm line if wet-season driving matters, which in Kenya it does.

Finding the truth without a gauge: tread-wear indicators — small rubber bars moulded inside the grooves. When the surrounding tread has worn level with them, the tyre is at replacement point. Free, built-in, checked in seconds during the daily walkaround.

Key takeaways

The tread ladder: new 8–9 mm → wet grip degrades from 3–4 mm → legal floor 1.6 mm — plan around the 3 mm line, not the legal one
Tread-wear indicators — bars inside the grooves — give a free, instant replacement verdict

Quick check

Your tyres measure 3 mm — nearly double the 1.6 mm legal minimum. Sorted?

A) Yes — well above the legal minimum, nothing to do

B) Legally yes, but you've entered the "worse wet grip" band — wet stopping and aquaplaning resistance are already degrading; start planning replacement, especially before the rains

C) No — 3 mm is below the legal minimum

D) Only if the tread-wear indicators are already showing