Buying running equipment is an investment. To get the most out of their trail shoes, many runners are tempted to use them on tarmac. While technically possible, this comes up against physical and physiological laws that are harmful to both your gear and your health.
1. Premature wear: why tarmac destroys the soft rubber of a trail shoe
The sole of a trail shoe is made of soft rubber designed to "bite" into earth or rock. On the road, this rubber undergoes constant thermal build-up.
Consequence: You risk reducing the lifespan of your lugs by 50% in just a few urban outings.
Key fact: Tarmac acts like a grater. With every stride, friction tears away micro-particles of rubber.
2. Increased risk of falling: poor grip from lugs on asphalt
Contrary to popular belief, a large lug does not provide better grip on the road — quite the opposite. Grip on tarmac depends on the contact surface area with the ground.
- Key fact: Lugs reduce the contact surface area by nearly half compared to a smooth sole.
- Consequence: On wet tarmac, water cannot drain away and creates a film between the lug and the road. This is the micro-aquaplaning effect: your trail shoes become unsafe.
3. Joint damage: the rigidity of a trail shoe can cause shin splints
A trail shoe is a rigid structure designed to protect against rocks (toe cap). On the road, this rigidity blocks the natural movement of the foot.
- Key fact: Tarmac does not give. Impact vibrations are not absorbed by the rigid sole and travel straight up into the shin.
- Consequence: Running on the road in trail shoes increases the risk of shin splints and knee pain due to a restricted foot roll.
4. Wasted energy: the unnecessary weight of reinforcements in the city
In sports science, every gram on your feet counts double in terms of energy expenditure.
- Key fact: A trail shoe weighs on average 30 to 50g more than a road shoe due to its lateral protection.
- Consequence: You tire more quickly. Over a 10km run, this represents a significant amount of weight lifted unnecessarily, degrading your running economy.
When does mixed use become acceptable?
While it is inadvisable to rack up kilometres on asphalt, your trail shoes handle link sections very well (the stretch from your home to the start of the trail).
Furthermore, while road running is off the table, you can absolutely hike in your trail shoes. At walking pace, the impact speed and heat build-up on the rubber are minimal, which means you can use your pair on towpaths or paved roads without any major risk.
