Dry Traction
Traction refers to peak, slide, and other forces submitted between the tyre and the road.
Dry traction usually refers to traction on an asphalt or concrete surface (it is worth noting that those two surfaces have different friction coefficients).
Dry traction relies on footprint elements that do not lose contact with the road surface when the tyre rotates.
An extreme example of dry traction can be observed in a race tyre. A race tyre tread has a very high contact area with very few voids.
The tread compound is designed to lose energy and build heat so the tread can become sticky and adhere to the toad surface.
Testing for Dry Traction
Dry traction testing is often conducted on an instrumented vehicle that can measure stopping distance and deceleration.
This testing can also utilise an instrumented traction trailer, which measures brake forces during peak and slide traction.
There are standard protocols for dry traction testing, as well as custom protocols specific to individual tyre or automotive OEMs.
Tread Attributes Benefiting Dry Traction
A tyre engineer seeking to optimise dry traction performance in a tyre may;
- Increase the contact area and decrease void areas, such as grooves, slots, and sipes.
- Minimise squirm in the footprint area. One way to achieve this is to maximise the tie bar to link the elements together.
This information has been reproduced with the kind permission of Smithers
Smithers is an independent, third-party testing and consulting company with a history in the tyre industry starting back in 1925. Their team has many years of experience in the tyre and rubber industries and have created this information as an educational resource on the general science behind tread development.
As an organisation, Smithers do not actively develop tyre treads for commercial use in the market.
Tread design is a complex, highly specialised activity that must take into account each manufacturer’s design and development goals.
© SMITHERS, 2021