22 Mar 2016


With so many variables, tires are about as far from the cliché of being merely ‘black and round’ as they can be. It’s true for road tires and for mountain bike tires, but with even more variables of surface conditions and riding styles to apply to off-road riding, MTB tire choice is a great area to explore. At times, selecting the right tire can seem more a black art than a science – let’s demystify that.

At one end of the scale you have light, minimally treaded tires that accelerate and roll very rapidly, while at the other you have sticky, aggressive treads that grip hard – but roll slowly. Which is right?

On the road, light and fast-rolling is pretty much the end of the story. But off road, things are more complex. A ‘fast’ tire isn’t always fast. Or at least, the fastest tire isn’t always the lightest, easiest-rolling one.

A ‘slower,’ grippier tire you’re confident in can be faster over a challenging ride or race. The less time you spend tensed up and braking – let alone lying on the floor – the faster you go.

Get the right tires on the right rims – and have fun!

What type do I need? 
For dry or hardpacked surfaces, tires with low-profile treads put down a lot of rubber with little rolling resistance. In mud, however, they’ll almost immediately clog and slide out.

For mud, tires with tall, widely-spaced knobbles dig in without clogging. Full-on mud spikes are fast-rolling and hugely grippy, but on hard ground they are unstable, sketchy and ultimately slow you down.

For rocky or rooty terrain, wide tires with soft compound (55a or less) and tough yet compliant sidewalls find the best grip. Use with low pressures (25psi or under).

For mixed surfaces, an all-rounder is best – at least on the front. It gives you the steering and braking you need to confidently take speed through sketchy sections. Combine it with a rear tire that has a lower profile, closer-spaced knobbles (and running around 5-8psi more pressure) to keep rolling speed up. Rear slides are far easier to control, can keep your overall momentum up, and keep your adrenaline levels high!

What else should I consider?

• Width
Measured in inches and typically between 1.9in and 2.35in, you’re unlikely to benefit from anything wider or narrower. Big volumes allow lower pressures and greater compliance for confident grip. The downside is drag, especially on smooth surfaces.

Narrow tires work well in very loose or wet ground, as they dig in rather than ‘float’ on top, but even this is a preference – plus low-volume tires struggle more once you hit rocks, roots and hard other surfaces.

Think carefully about the kind of surfaces and conditions you’re expecting to encounter during each season – different sets of tires for different times of year are highly recommended, and a spare set of wheels is a great help.

Thin sidewalls are light, but they’re susceptible to cuts and pinch punctures and can’t cope with low pressures – so they’re no good in harsh terrain. There’s a growing choice of armored sidewalls, which offer much of the strength of old ‘dual plies’ with less weight. Tubeless tires have very heavy sidewalls but with no tube that evens out, and time-wasting punctures are pretty much banished.

• Compound
Multiple-compound tires are expensive, but work. Some combine hard central strips with soft shoulders, while others lay soft rubber over more stable, harder bases. They’re a great compromise of grip and rolling speed.

Two final things to bear in mind

• Your rims
Wider rims, such as those on the K-ForceSL-K and Afterburner ranges, create a more stable base and a squarer tire that helps with cornering grip. They increase volume and support low pressures well – wide-but-light rims are a huge boost off-road.

  • K Force Light MTB 27.5 front grey wheels

All FS MTB wheels, including the K-Force 27.5s pictured here, feature 26.1mm wide rims

If your rims are narrow (under 19mm), avoid tires wider than 2.1in. They’ll blow up in a balloon-shape that reduces cornering grip, and they can roll away from the rim under hard cornering. With the K-Force, SL-K and Afterburner ranges all featuring 26.1mm wide rims, you won’t encounter that problem with FSA MTB wheels!

• Your pressures
A pressure change of 1-2psi makes a noticeable difference, while 5psi can transform characteristics: note the front pressure should be lower than the more heavily-loaded rear. So it’s worth experimenting with different pressures while keeping all other factors (your bike setup, including suspension, but also the route, weather conditions and your own fitness) the same for comparison. Find your sweet spot – and ride it!