Know your tyres

AIR PRESSURE

Different tyres require specific air pressures. A rough rule of thumb is: the thicker the casing, the lower the air pressure you can get away with. Equally the bigger the volume, the lower the pressure. For maximum comfort and grip, aim for the minimum pressure that keeps the casing from twisting too much and still prevents rim strikes under impacts. Experiment with lower pressures if you often run over 30psi.

CASING

Casing thickness and precise ply lay-up has a big impact on ride quality and affects conformity, rolling speed and durability. Harder charging riders might have to accept the extra weight of meatier casings to prevent punctures and stop sidewalls folding under cornering forces. Heavier tyres accelerate more slowly, but feel more planted and stable once momentum takes hold. Tubeless is always the way to go – inner tubes feel dead and lifeless, and are generally more susceptible to punctures.

SPECIFICATION Weight: 1,170g • Size tested: 29x2.5 WT • Actual size: 60.1mm • Contact: extrauk.co.uk

The Maxxis High Roller II is a classic allmountain and downhill tyre. Its 10-year-old design uses chunky edge blocks for cornering bite separated from aggressively-ramped central paddles (that roll fast one way and brake hard the other) by a wide and welldefined ‘grip channel’.

The High Roller II has been re-engineered to fit today’s wider rims, but has fallen from favour a little, likely due to newer and more hyped models appearing on the market. So using it as a rear control tyre on enduro bike tests recently has been like getting reacquainted with an old friend.

There’s a near-perfect balance of grip, reasonable rolling speed and superb braking bite, even in the wet or on looser dirt. Two

120tpi layers in this DD version make it tough and resistant to cuts and damage in most UK terrain, and still a little lighter to drag uphill than most other enduro/dh halfway-house options. It’s also comfortable and dull, if not quite as conforming as the (almost 200g) lighter EXO model that deforms better, but also rips more easily in rocky areas.

The HR II is great on the rear where the distinct space between the shoulder and central blocks adds dynamism and facilitates aggressive lean angles. This groove also delivers a ton of cornering hold and off-camber bite, and the tread seems to rail turns and cut into banking, even when pitched right over.

This broad grip channel is shared with the (faster rolling/worse braking) Maxxis Dissector, and, like that tyre, the HR II can feel a bit vague on the front with less continuous cornering grip than an Assegai; another reason its popularity may have waned, and one of the main reasons why we prefer it as a rear option.

Like plenty of other Maxxis tyres, there’s the right blend of suppleness, support and damping here. Some brands excel in one area but few offer such assured all-round performance as the Taiwanese firm. The only things preventing a perfect

10 are the £75 price tag and the fact that the ramped blocks lack bite on slimy climbs.

SPECIFICATION Weight: 1,118g • Size tested: 29x2.4in • Actual size: 59mm • Contact: silverfish-uk.com

One of two totally new Michelin trail/enduro tyres, this second-generation Force AM is the brand’s more tightly-treaded trail tyre. Available in 2.4in and 2.6in sizes, and 27.5in and 29in diameter, it’s designed to be lighter and faster-rolling than the popular Wild Enduro with a low-profile central tread, beefier edge blocks and a new rubber compound. Michelin is basically targeting the kind of UK terrain where a full-on enduro tyre is overkill, but you still want toughness and reliability.

At first glance, with directional arrowshaped central tread blocks, the Force looks rear-specific. The ‘triple offset’ shoulder knobs derived from the DH22 downhill tyre are slightly taller though, meaning it’s suitable for front use too. These cuboid side blocks work in sets of three, pointing inwards in the rolling direction (the visual effect is reminiscent of WTB’S Vigilante), whereas the central band is pretty low in height and tightly packed.

The complicated construction incorporates triple-ply layers of 60tpi belt plus an extra puncture protection liner inside the Gravity Shield 2 casing. Like other recent Michelins, this all proved extremely robust, but all the

reinforcement means the weight is high for what is (in theory) a less-aggressive trail tyre.

On a broad variety of tracks and surfaces, the Force proved to be a sorted product with no bad habits and consistent grip without any dramatic transitions when leaning over. The latest GUM X rubber blend uses a firmer central band, so rolling speed is decent, and damping and friction are roughly on a par with a Maxx Terra Maxxis, if a fraction less grippy. Don’t go expecting a trail version of the ridiculously sticky Michelin DH compounds, but thankfully, that means you don’t have to put up with side effects of drag and sluggishness either.

The tough Force AM 2 makes for a decent rear tyre that can handle spikier, rocky terrain, but plenty of riders might want sharper teeth up front, or to bite into looser, frequently wet UK surfaces. The 1.1kg weight is felt when climbing too, and without much sense of faster rolling than meatier, more versatile treads like the High Roller II, we’re not sure this new model is that compelling an option in a crowded marketplace.

SPECIFICATION Weight: ‘S’ 1,121g, ‘R’ 1,131g • Size tested: 29x2.4in • Actual size: 60.9mm • Contact: extrauk.co.uk

Pirelli’s re-imagined Scorpion represents the relative newcomer’s second-generation mountain bike design. Trail and enduro versions are available; the latter here with a meatier tread and casing suitable for all-mountain riding.

With multiple lug sizes, orientations and a more directional layout, the complex new Scorpion stands out from most blockier designs in its category that frequently resemble either popular Maxxis tyres or uniform motocross rubber. Both the S and R versions tested have unique treads too, targeting soft conditions and rear use respectively. They share offset shoulder blocks with alternating knobs, but the R gets lower-profile central paddles that are perpendicular to the rolling direction.

Unusually, Pirelli use a single SMARTGRIP compound throughout, which claims high grip in both wet and dry conditions. Enduro models use multiple reinforcement layers including a rubber tread wrap and sidewall bumpers to reduce pinch flats too. They were the easiest tyres on test to install, and held air perfectly.

Both models have a unique high-energy feel and roll almost unbelievably fast considering

the reasonably aggressive tread patterns. The flip-side of the extreme pace and lively ride is that they’re seriously springy and undamped. Whatever the pressure, expect to bounce and skip over small bumps and hollows – this tyre apparently gains and maintain speed by not squishing much to maintain contact and ground control. This trait even saw our test bike bottoming out where other tyres didn’t with the exact same shock pressure; Pirelli’s rubber and casing clearly absorbs way less impact energy.

This disconnected behaviour translates to a very nervous feel over roots and rocks and edgy cornering where the comparativelysmaller offset shoulder blocks flutter and chatter at any lean angle, rather than smearing or holding fast for traction and grip.

Tough and super-fast rolling might work for eking out big miles, but, we disliked the edgy, nervous feel and believe that most riders, whatever their level, will seek a tyre with more security and confidence than the Scorpion.