Your tyres make a massive difference to the character and ride of your bike. We bring you the lowdown...
Tubes or tubelesss?
Traditional tyres use an inner tube to keep them inflated, but how do 'tubeless' tyres work?
Tubeless tyres ditch the inner tube in favour of a tyre that's specifically designed to be airtight, either though the use of an additional layer of rubber, or through the use of a latex-based sealant.
Mavic's UST (Universal Systeme Tubeless) system uses thick side-walled tyre locking into a specific sealed-bed UST rim. The advantage is an airtight seal with or without a sealant liquid inside, and very stable, pinch puncture-resistant, low pressure performance. The downsides are that these tyres are more expensive and also heavier.
Most mountain bike tyres on the market today use some sort of 'tubeless compatible' system. These tyres use a tubeless bead but require sealant in order to make them airtight. They also require rim tape to seal the spoke holes off.
The benefit of this system is that it is lighter than a full UST system and offers the user a wide variety of tyre choices. The downside is that there is not established standard between the various tyre and rim manufacturers, so some rim and tyre combinations make work better than others. Even so, this is the most common tubeless option you'll encounter.
Interested in learning more about tubeless conversions? Check out our guide to setting your bike up tubeless.
Light vs heavy
Weight has a big effect on the agility and acceleration of your bike. Light tyres are much easier to spin up to speed, change direction with and even stop, so make sense for cross-country use.
Heavier tyres are generally thicker, which means they resist punctures and pinch flats better and are less likely to flop and roll off at low pressures. Heavier tyres also increase the gyroscopic effect of the wheel, making the bike more stable on the ground or in the air.
At the really heavy end, reinforced-carcass downhill tyres are designed to be run at super low sub-20psi pressures without popping or tearing off the rim, and rely on gravity help to get their 1kg-plus weight moving.
There's a massive range of tyre widths available from 1.5 to massive 5in fat bike tyres. The majority of mountain bikers run tyres in the 2.2 to 2.5in range. This is because they offer good protection and grip for more aggressive riding. Tyres narrower than this offer less cushioning and have less 'footprint' to grip with. Pinch flat resistance is lower unless run at higher pressures too. They are lighter and roll faster though, and often cut through sticky mud and gloop better.
Square-profile tyres have more edging grip but are harder to lurch into corners. Rounder tyres roll more easily into corners and slide more predictably. Edge grip isn't as aggressive though.
Speed vs traction
It's slightly simplistic but true that tyres that grip well because of sticky compounds and tall square-edged knobs drag more than those that don't.
But within this generalisation there are some notable tyres that add speed by the slight sloping of tread patterns, multiple tread compounds or use of a 'fast' carcass. Conversely, some tyres that have barely any tread actually bite as well as some mid-knob rubber.
- Shoulder – The edge tread that provides off-camber and cornering grip.
- Sidewall – The bare side of the tyre. Double or 'two ply' on DH tyres for extra stability and pinch flat resistance; airtight on UST tyres for tubeless running.
- Bead – The steel wire or Kevlar cord at the base of the sidewall that locks into the rim lip to keep the tyre in place. Kevlar or Aramid fibre beads are lighter and let the tyre fold, but are more expensive and the tyre is more likely to fall off if flatted.
- Carcass – The fabric body of the tyre made from overlapping weaves. A more supple carcass enables the tyre to deform around lumps for extra grip but is less stable at low pressures. A reinforced carcass is more protective and less wobbly at low pressures but heavier and less comfortable. Lighter carcasses are more likely to get point punctures too.
- TPI – The number of threads per inch in the carcass. Tyres with more threads are generally higher quality with a more subtle feel, but companies like Tioga use a smaller quantity of fatter threads.
- Multi-compound – Tyres using different rubber compounds. Dual compounds are normally harder in the centre or underneath for fast rolling and long life, but soft on the shoulders for cornering grip. Schwalbe and Maxxis now do triple-compound tyres too.
- Durometer – The softness rating of the rubber; 70 and above is hard, 60 medium and anything below 50 soft. The softer the tyre the stickier it is on rocks and so on, but the faster it will wear out.