Buyer's Guide to Mountain Bike Tyres
By BikeRadar | Monday, August 13, 2007 11.00pm
Grouptest - Ripper grippers Paul Smith©.
Your tyres make a massive difference to the character and ride of your bike. We bring you the lowdown...
Tube or no tube? Flat is the question
Traditional tyres use an inner tube to keep them inflated but how do 'tubeless' tyres work?
Most designated tubeless tyres use Michelin and Mavic's UST (Universal Systeme Tubeless) system with a 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 higher price and awkward fitting which relies on a clean rim and tyre for a good seal, plus a big-volume pump to blow it up.
Clean tyres and track pumps are distinctly rare mid ride, and even with a C02 cartridge you'll normally have to use an inner tube to get you home and repair the tyre later. While small holes are repairable, a big hole can mean the tyre is written off too.
Tubeless kits such as Stan's No Tubes allow you to create your own tubeless set-up using a latex-based liquid mix and rubber rim strip to seal the inside of a conventional tyre and rim. You still get most of the anti-pinch puncture and low pressure advantages of a UST set-up but with an almost unlimited choice of rims and tyres - or just your existing ones - with only the initial kit cost and latex top-ups to pay for. These are also lighter than UST set-ups. The same awkward on-trail repair problems apply though, and the tyres are less stable than UST models and can even roll off under big cornering loads.
Bontrager have introduced a halfway house Tubeless Ready system which uses a lightweight but mainly airtight and UST style sealed-bead tyre that can easily be fully sealed onto a tubeless rim with their latex style Super Juice. This potentially gives the best of both worlds and it's looking good so far, plus it's cheaper than full UST.
Light vs Heavy
Don't forget the big effect of weight 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 point puncture 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 DH 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 kilo-plus weight moving.
There's a massive range of tyre widths available from 1.5 to 3.0in, but in this test we've mostly tried 2.2in plus trail tyres and 2.5in plus DH tyres. 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 fl at 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 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.
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