The short answer is: a lot!
I can remember a trip to the Brecon Beacons several years ago where I was ridiculed the whole weekend for making the convoy stop at a local bike shop as I needed to buy some new tyres as I’d decided en route that I’d brought the wrong tyres for the trip. The guys I rode with were shocked I had more than one set of tyres for my bike. And I was shocked that they didn’t. Over the weekend I got up and down every hill, often when the others couldn’t. I’d like to believe that was because I’m a much better rider but the truth is that a good part of it was down to the fact my bike was set up properly. The tyres are the only bit of the bike that touches the ground, and I like to keep it that way.
So, how do you choose the right tyre? There are five factors to a tyre that affects its performance: width; tread pattern; puncture resistance; compound; and weight. Each of these factors has a different affect on tyre performance. You can bias one factor over another and get a different performance. You can also take an average throughout and get an all-purpose tyre, and for the casual rider that’s probably all they need. However, if you’re riding and you find you can’t get traction when you need it, or you struggle when the ground is wet, or you slip over roots or slide out in corners then perhaps the shortest route to better performance is to put better tyres on your bike. Better doesn’t necessarily mean more expensive, it just means better suited to the trails you ride on.
Mountain bike tyres come in a wide variety of widths from about 1.5 inches to 2.5 inches, and that inch makes quite a difference. Although, it isn’t really the width at all, but the volume, but tyres are sold by width. This in itself is a bit of a red herring because the actual width of the tyre depends on the width of the rim you’re putting it on. A narrow rim tends to make for a narrower tyre and a rounder profile. A wider rim makes for a wider tyre and a squarer profile. The immediate effect of this is if you have a wider rim you can put a narrower, lighter tyre on a wider rim and get the same grip. So, should you go wide or narrow? A narrow tyre is light, so good for racing where weight (discussed later) is important, but also good for wet and muddy conditions. Narrow tyres tend to cut through the gloop and bite in the harder ground under the mud. Wider tyres give you more contact with the ground, but also are better at absorbing shock so less likely to pinch the inner tube when you hit a root and cause a flat. So, wider tyres are better for faster, downhill sections. One additional consideration is the width of your wheel rim. If your rim is quite narrow then a wider tyre can perform badly, or even fail as the large volume is held on in a narrow area which comes under some great forces when cornering fast, occasionally causing the tyre to roll off. If you’re unsure then stick to tyres less than 2.3” on standard mountain bike rims. Remember too that on a wider rim, any given tyre with comes up wider than on a narrower rim.
The bigger the knobbly bits on a tyre, the more traction it’ll give you in loose or muddy conditions. However, too big and they give too much resistance and you’ll find them hard work in all but the muddiest sections. The wider the spacing between the knobbles the easier it’ll shed mud, stopping your wheel from clagging up. But, on hard ground, only the knobbles get traction so if there are too few, the tyre won’t grip. So, tread pattern on your tyre is an important consideration and will be determined by where and when you’re riding. Most of the time though you’ll be making a compromise somewhere. There are plenty of all-round tyres out there that cope well enough in most conditions and it is possible to fit one of these tyre and use it all year round. Most riders however choose two sets of tyres, a mud specific one for the winter, and a more general purpose one for the rest of the year. This gives you the best riding without the need for a shed full of rubber. Mountain bike racers will tend to go for a faster rolling tyre that wastes less energy and moves faster, using their high skill levels to compensate for a lack of traction.
Puncture resistance / weight
This is an often overlooked area in tyres. Cyclists love to have the lightest kit, even tyres. The way to make a tyre more puncture resistant is to have a closer weave of fibres beneath the rubber, or to have a thicker layer of rubber. This makes the tyre heavier, and although the weight of the tyre is important, particularly so as the rolling weight of the tyre has a big influence on how a bike rides, you usually lose more time repairing a puncture than you do from a higher rolling resistance. A puncture resistant version of a tyre usually adds around 60g of weight to it. 120g of weight to stop punctures is an excellent trade off, especially as there are easier areas to lose weight on a bike, often in unnecessary add-ons, but also from the large fleshy object situated just above the saddle.
A lot of time and money is spent by tyre manufacturers researching rubber compounds, and often modern tyres are made from several different compounds in the one tyre, optimised for where it is situated. A soft compound is excellent for grip in the dry, but can be prone to holding on to sharp objects that can puncture the tyre. Hard compounds are great for being hard-wearing and for biting through mud and soft surfaces to grip on more stable ground below. In general a softer tyre will be grippy in most conditions but the down-side to that is the tyre won’t last as long.
So, which tyre?
Choosing the right tyre can be a very personal experience. Ask 10 riders which is the best tyre for a certain area and you’re likely to get 20 different answers. The best way to decide which tyre suits your riding best is to try them out. Borrow from a friend, or get advice from someone who rides similar trails in a similar style to you. However, if you put together all the advice above you’ll get close to the type of tyre that will suit you, then go in to your local bike shop and ask them what they have that will suit. Then, get out and ride. Test the tyre on familiar trails in various conditions and see how it performs. See where it bites and where it slips. Also, try the same tyre with a variety of tyre pressures as the characteristics of the tyre change with pressure. My new winter tyres are out for testing now and I found at 40psi they were a bit skittish. At 35psi they’re fantastic. It’s only by riding and experimenting that we get to know how our tyres perform, but this isn’t limited to tyres, it’s all aspects of our bikes and our riding.
My favourite tyres
I like a 1.95” tyre with square knobbles that sheds mud well. My favourite is the Panaracer Trailraker. However, they don’t do those for 29” wheels so this winter I’ll be using Bontrager Mud-X in 2” width. I took them out on a wet ride recently and early tests are promising.
I like a wider tyre for great downhill speed and control. My favourite is the Continental Gravity, a fast 2.3” tyre. But I’m also rather keen on Schwalbe Rocket Rons which are fast and grippy in 2.25”
If you just want one tyre to run all year round then my favourite, and the choice of a lot of the the chaps I ride with is the Schwalbe Nobby Nic. It comes in 2.25” and 2.35” but the 2.25” seems to be the best performer all round. For a slightly narrower all rounder the Panaracer Cinder is a fairly decent tyre.