ALWAYS READ THE LABEL

Decoding the information on the side of your tyres

TPI: thread count

Standing for ‘threads per inch’, TPI is the number of threads within the fabric of the carcass. It’s widely accepted that a higher thread count (using a finer thread, just as with bed linens) means more supple tyres that will be lighter and have less rolling resistance, although they may be more fragile. In performance terms, the bigger the TPI number, the better (and more expensive) the tyre, but it’s not quite as simple as that. A high TPI might be because a brand has added together multiple plies of lower TPI fabric – so a tyre with three plies of 60TPI might be quoted as having 180TPI. Most road tyres range between 60TPI at the bottom end to 120TPI for high-quality race tyres, so a TPI count much higher than that will likely be multiple plies.

Tyre width

The stated width of a tyre can be deceiving. For instance, it can be affected by the internal width of the rim. A 25mm tyre mounted on a wide 21mm (internal) rim might actually measure closer to 28mm once inflated. Also, size is not always comparable between brands: a Mavic 25mm tyre is likely be skinnier than a Continental 25mm, for example. What’s more, a tyre’s width may stretch by 1mm-2mm over time.

Pressure

The amount of air you put in your tyres will alter their grip, handling, comfort, even durability. Finding the correct pressure will depend on rider weight, surface conditions, air temperature… It’s confusing, but our own tests (see issue 43) suggest most people run tyres too hard. Manufacturers tend to recommend inflating 25mm tyres to over 100psi, but our data suggests around 85psi is the fastest set-up for UK roads.

Additives

Adding compounds to the rubber can improve performance elements such as elasticity or longevity. Common additions include silica and carbon black (which gives tyres their black colour), but manufacturers have experimented with more exotic additives. Graphene is heralded as a ‘super substance’ and has been used by Vittoria to enhance the properties of its rubber compounds, claiming it increases grip and durability while reducing rolling resistance. Vredestein has taken a different approach, using natural rubber from the root of the Russian dandelion plant, instead of rubber imported from Asia. This, it claims, is not only more sustainable, but also its slightly higher natural resin content results in a little more grip (2%) and less rolling resistance (1.5%).