Analysing gravel route surfaces before you ride

Why the surface matters more than the route itself

On gravel, two routes of the same distance and ascent can call for completely different kit depending on what's under the wheels. A route that's 80% tarmac rides fine on narrow, high-pressure tyres; the same distance on a rocky track calls for wide tyres, low pressure and sometimes a different drivetrain. Surface type doesn't show on a standard map — it needs checking.

What surface detection shows

An imported track can be coloured by the real ground surface, split into seven categories: tarmac, compacted, gravel, dirt, grass, cobbles, rock. Every part of the track takes on the colour matching what it's made of, drawn from existing map data.

A concrete example

A route showing 86% dirt, 9% gravel and 5% tarmac reads very differently from one showing 60% tarmac and 40% compacted track: the first calls for a gravel or MTB bike and wide tyres, the second stays rideable on standard gravel setups, even road bikes with semi-wide tyres on some models. The exact percentage directly changes the answer to "which bike do I take?"

Gravel or MTB: where the line sits

A high percentage of dirt or rock doesn't automatically rule out a gravel bike — it also depends on the gradient tied to those technical stretches. A flat, rolling dirt track rides perfectly well on gravel; the same surface on a steep, uneven slope leans more towards MTB territory. That's why surface always reads best alongside ascent, never on its own.

Reading the percentage breakdown

A chart sits alongside the coloured map, summarising the breakdown as a percentage — 86% dirt, 9% gravel, 5% unmapped, say. That last figure deserves attention: an unmapped stretch isn't necessarily a problem, but it's worth checking on a satellite view before you set off, especially if it makes up a large share of the route.

Cross-referencing surface with ascent

A high gravel percentage on a flat profile doesn't raise the same questions as a high dirt percentage on a steeply climbing profile — the second combination wears through tyres and drivetrain faster. The guide on reading an elevation profile covers how to spot these sections before cross-referencing them with the surface.

What it changes for your kit

Without giving a universal setting — every bike and every rider has their own habits — the result steers concrete choices: tyre width, starting pressure, whether to run tubeless inserts, even whether to pick a gravel bike over a road bike if the non-tarmac share passes a certain threshold. It's information to check before loading the bike into the car, not after.