# The number that matters is at the thinnest point

> A brake pad diagram runs 12mm new down to 3mm worn, with the limit drawn at 2mm — and a note that the reading has to come from the thinnest point, not the easy one to see.

August 19, 2026 · https://justog.club/stories/brake-pad-wear-indicator

Two brake pads, drawn in section, side by side. One dimensioned 12mm. The other, 3mm. A dashed
line runs across both of them, labelled min 2mm. Beneath the pair, one instruction: measure the
thinnest end.

Twelve down to three isn't the number that decides anything. Two is.

## What is this diagram actually measuring?

How much friction material is left before the pad stops being a pad and starts being a piece of
metal against a disc.

A new pad here starts at 12mm. Worn down through ordinary use, it reaches 3mm in the drawing — and
the dashed line at 2mm marks the point past which it shouldn't be run any further. The two sectioned
pads aren't before-and-after decoration; they're the same object at two different points on the
same scale the dashed line sits on.

## Why does the instruction insist on the thinnest end specifically?

Because a pad doesn't wear flat, and the easy place to look is rarely the place that's closest to
the limit.

Pads wear at an angle more often than not, thinner at one edge than the other, so a glance at the
thicker side gives a comfortable reading that's simply wrong. Measure the thinnest end is the
entire content of the diagram below the numbers — it's telling the reader which of two available
answers to trust, because one of them is a guess dressed up as a check.

## What makes a good version of this design?

Keeping the two pads honestly uneven, rather than drawing them as clean rectangles that happen to
carry different numbers.

A pad drawn as a flat block with 12mm and 3mm written on it is a label. A pad drawn with a visible
taper toward one edge, with the dashed line crossing it at an angle rather than square, is a
diagram that actually shows why the instruction exists. The unevenness is the point being made, not
an imperfection to tidy away.

## Who owns a wear limit like 2mm?

Nobody specific. A minimum friction thickness is a safety figure published widely across the trade,
not a proprietary number any one company controls.

What is owned is a particular manufacturer's own pad design, its part number and its printed
packaging — licensable if a real one is the point of the shirt. Left generic, the drawing stays a
plain diagram of a fact about wear, which is exactly what it needs to be to make its point.

## Does this only matter for brakes?

Any wearing part measured against a minimum works the same way — a clutch friction plate, a tyre's
tread, a cutting edge ground back over years of sharpening.

It sits close to
[the advisory that records the gap between acceptable and not yet failed](/stories/mot-advisory-list),
except this diagram is the method behind that judgement rather than the record of it: the advisory
says a pad was close to the limit, and this is the drawing that explains how "close" gets measured
honestly in the first place.

## Isn't this just common sense — of course you check the worst spot?

It should be, and the fact that it needs saying at all is the actual subject of the diagram.

Checking the visible edge is the natural thing to do, because it's the part you can see without
turning the pad or getting a light on it properly. The instruction exists specifically because the
easy check and the correct check aren't the same one, and a diagram that only showed the numbers
without saying where to take them from would let that mistake happen just as often — the same
caution behind
[setting a valve clearance cold rather than trusting a convenient hot reading](/stories/valve-clearance-table).

## Does it print well?

Yes — two pads in flat section with hard dimension lines are simple, sturdy shapes.

Cream for the pad outlines and the dimension figures keeps the drawing readable against charcoal;
red carries the min 2mm line and the instruction beneath it, so the eye lands on the limit before
it lands on anything else. Keep the two pads at a clearly different size rather than a subtle one —
the contrast between 12mm and 3mm is doing real work and shouldn't be softened for symmetry.

## How do I get one made?

Describe your diagram at [JustOG](/) — the figures, and whether to keep the taper across the worn
pad. Pick a direction, drag the crop frame, see it composited on the real garment, and it's made to
order and shipped.

Designs other people have published are in the [shop](/shop).

Twelve millimetres new, three worn, and the reading taken from wherever it's thinnest.