Your guide to buying bicycle tyres

“What are the best bicycle tyres for…?” is a question for which the term “Frequently Asked” could have been invented. It’s hardly surprising – there are hundreds of tyres on the market and with few exceptions they’re all good at something. It’s just a question of figuring out what you need yours to be good at and figuring out which ones they are. So join us as we take a brief spin around the tyre firmament and try to arm you with some all-important knowledge on the way.

We’re not going to make specific recommendations here, partially because in an ever-changing tyre market whatever we recommend will be replaced in a few months but mostly because we don’t know what, where and how you ride. But read through the points above, combine that with what you’ve learnt about the behaviour of the tyres you’ve got and you should be able to figure out what to look for in your next pair.

It’s also a good idea to see what other local riders are running. If there’s a majority vote then they’re probably on to something, although bear in mind that a lot of people have settled on a favourite tyre and just keep buying them even though there might now be something a bit better. If you’re really lucky you might find a local tyre geek who’s tried everything and still has most of them in his garage – with a bit of persuasion you can probably try a few of his cast-offs (they’ll still have loads of life left in them…) to try to narrow down what you like. Read the user reviews and look for people who ride in similar conditions to you but remember that riding style counts for a lot.

With that said, here’s what you need to know…

Construction

Look at a tyre and you probably see a black rubbery thing. But as with so many things the important stuff is hidden away underneath…

The foundations of a tyre are the beads, the strong strands that lock in to the rim under air pressure to keep the tyre in place. They’ll either be steel (strong, cheap, heavy) or Kevlar (strong, expensive, light). Kevlar beads have the added benefit that they let the tyre fold up into a smaller package, a boon for warehouse owners and expedition tourists.

Strung between the beads like thousands of tiny hammocks between steel trees are the strands of the tyre casing itself. The casing is what gives the tyre its shape, and it’s usually made up of strands of nylon. They’re “biased”, that is they run at an angle across the tyre. Or more correctly a couple of angles, with different layers (or “plies”) running in different directions. The thickness, number and orientation of the strands in the casing determines how stiff the tyre is.

Stuck to the outside of the casing is the tread, which is the black rubbery bit. Some tyres have an additional belt running around the circumference under the tread for an added layer of puncture protection. Slick tyres are just smooth rubber, treaded tyres have the tread moulded in – all those little hairs that you see sticking out of a new tyre are leftovers from the mould.

Tyres are generally black because carbon black has been added to the rubber to improve wear resistance. Some tyres are available in different rubber compounds to afford extra grip. On soft surfaces it’s the actual tread that’s doing most of the work so the rubber compound doesn’t make all that much difference, but on harder trails there can be significant benefits to softer rubber. Unfortunately softer rubber wears out quicker – your choice…

Size and weight

We’ve lumped these together because as one goes up, generally the other one does too. Also tending to go up is puncture resistance, drag and grip. There’s a huge weight and size range in MTB tyres, with XC race tyres available down to 1.5in and sub-400g and DH monsters up to 3in and over a kilo. Size is the most obvious factor in a tyre’s weight, but it’s far from the only one – it’s entirely possible for two equally-sized tyres to differ in weight by a couple of hundred grams.

Tyres with bigger, gnarlier treads will weigh more – rubber’s pretty heavy and bigger tread blocks need more rubber. Some tyres extend the rubber all the way to the bead on the outside (and often the inside) of the casing for extra reinforcement against sharp rocks, wayward brake pads and the like. And the casing itself can vary in weight a lot, with extra layers, thicker or more closely-packed fibres for improved strength.

Then there’s the beads themselves. Kevlar beads are lighter than steel, and are a common way of getting a tyre’s weight down without compromising durability or grip. They can only save a bit of weight on their own, though, so any markedly light big tyre will have to have been slimmed down elsewhere to make the weight, and this may have consequences for puncture and abrasion resistance and wear characteristics.

Tread

There’re many factors to consider when sitting down to design a tyre. You need grip in all sorts of different directions, but you probably want something that rolls reasonably quickly too. Then you’ve got to try and make the thing work in a fairly wide range of conditions and ground surfaces and get it to hold on to the ground without picking too much of it up. And of course you’ll probably want to make it look different from everyone else’s tyres too. There’s enough conflicting requirements there that it’s a wonder no wars have started…

It’s apt to cause confusion, but we’ll try and pick our way through it all. The first thing to look at is the shape of the tyre. You’ll either find fairly shallow side knobs that give the tread a rounded profile, or big tall side knobs that make the tyre look squarer. This is looking along the tyre, obviously. If a tyre looks square from the side it’s probably worth avoiding.

In general (and this is a generalisation of ocean-rivalling breadth) square tyres grip more in corners but when they stop gripping they do so very suddenly. Rounded tyres tend to have slightly less grip but when it runs out they begin to gently drift rather than just falling over. This is what that “progressive feeling” that you may have read about in tyre reviews is all about. It’s a bit like brake modulation – you’ve either got an on/off feel or a linear relationship between input and output. And like brakes it’s easier to get the best out of a progressive system, but if you work with it you might be able to yield higher performance from something with an abrupt transition.

As you’d expect, the characteristics that the tyre profile would suggest can be substantially modified by the nature of the tread blocks that make up that shape, and this is where things start to get out of hand. There’s about a million different tread patterns out there, from simple square blocks to multi-faceted buttressed trapezoid strangeness.

To make sense of it all it helps to think about what the tyre’s trying to do. At the simplest level MTB tyres need to operate along two axes. First they need to grip fore and aft, putting tractive power down at the back wheel and braking power down at the front. Then they’ve got to grip from side to side to stop the bike slithering sideways off the trail in corners. Most of the time that’s all you need, hence the generally excellent all-round performance of tyres with generally square tread blocks across the casing – the edges across the bike grip fore and aft, the edges along the bike grip sideways.

There are good reasons for doing something more complicated, however. Serried ranks of regularly-spaced blocks work fine and leave handy gaps between them through which mud can escape rather than blocking the tread. But those gaps can also make for a noisy, slow-rolling tyre on hard surfaces. This is why old “paddle steamer” tread patterns fell out of favour a bit – loads of traction on soft stuff but a bit draggy on better going.

The easiest way of making a tyre roll faster is to overlap the blocks so that on hard surfaces the tyre’s always sat up on them, rather than the trail falling in to the gaps between them, if you see what we mean. Of course if you overlap the blocks then you’ve blocked the escape channels for mud, so designers fiddle around with the shape of the blocks to recover some clearance ability.

That’s one approach. Another way is to just make all your square blocks a bit smaller and fit more of them on to the tyre by putting them closer together. Narrow-spaced blocks roll faster but at the expense of grip on the softest surfaces. The trade-off between traction and drag is probably the key one in tyre design.

Another factor is off-axis grip. While most of the time tyres are only called upon to operate fore and aft or sideways, occasionally (or more often for some riders on some trails) you’ll encounter situations that require the tyres to grip in some other direction. Angled steps, root networks, off cambers, squiffy landings – all will benefit from a tyre that can handle stuff coming at it from other than the two “standard” directions. This is what the more complex tread designs aim to achieve with angled blocks of varying sizes. The rules of thumb about the effects of profile, spacing and escape paths still apply, though.

All tyres are a compromise and which end of the compromise you choose depends on your trails and riding style. If you’re a smooth rider on hardpack then you can take advantage of a fast-rolling tyre – you’ll have grip to spare anyway. If you ride less well-kempt trails and ride aggressively you’ll be looking for maximum grip and if that means they roll slower then so be it. Most people will fall somewhere in the middle, so it’s no surprise that most tyres out there aim for an even split.