Mountain bike tires are some of the most complex, yet under-appreciated components on today’s mountain bikes. For many people, a tire is nothing else than a rubber tube filled with air, but in reality there is much more involved.
What makes tires so complex?
First of all there are a multitude of parameters and components to a tire. There is the tread, rubber compound, casing, bead, inner peace (yes, that’s actually a part of a tire) and optional protection layers to name the major ones. All these components interact with each other, but also with the ground, the bike and the rider. Changes to one of these components most often lead to ripple effects. A change to the tread design, for example, can make the tire more vulnerable to punctures, so a protection layer might be included, which changes the rolling behavior of the tire, which then needs to be counter-balanced by making changes to the carcass, and so on and so on. A specific attribute of the tire is not just influenced by one of the components, but sometimes by every single one of them. It’s not only the tread which determines the rolling resistance of a tire, but also the carcass and the rubber compound. But making a change to these components also changes other tire attributes, like the grip or durability. All these dependencies make the design, but also the selection of the right tire a complex task.
Why haven’t this all been optimized yet?
To optimize something (in the mathematical sense), there needs to be an undisputed objective function which clearly defines that one tire is better than the other. But there are different objectives and different riders weigh them differently. A cross-country racer wants a tire that gets him to the finish line the fastest. He needs a tire which is light and rolling fast as these races are won or lost on the climbs. A downhill racer wants a tire which has a ton of braking and cornering grip and can handle the enormous forces of a downhill race. The occasional rider doesn’t want to be concerned about punctures, have reasonable grip and a tire which lasts a long time, so he doesn’t have to worry about it too much. So in short, there are different priorities. This could only be optimized, if it would be possible to build a tire which is faster, grippier, lighter, more robust, more durable and more comfortable than other tires.
Unfortunately that is not possible as some of these objectives are contradicting. The lightest tire will not be the most robust. The grippiest tire, will not be the most durable. And the fastest tire will not be the most puncture resistant.
In addition, the conditions vary as well. Trails range from hardpack over sand and gravel to sharp rocks or slippery roots. A tire optimized for sandy conditions, might not be the best for slippery roots and vice versa.
Lastly the riders and their preferences vary as well. Different weight, riding styles, but also different bikes demand for different tires.
With all these different objectives, conditions, dependencies and side effects, it’s clear that there will never be a one-fits-all mountain bike tire. Instead there will always be a huge offering and it’s up to the consumer to pick what’s best for him. The purpose of this website is to help you getting a handle on this challenge and see beyond some of the marketing language manufactures are throwing at you.
So let’s start with the requirements for mountain bike tires in no particular order:
- Grip describes the friction between tire and ground which is important while cornering, braking and accelerating (or climbing). A lack of grip means you’re not able to get your power translated into forward motion, the bike is refusing to drive into the direction you want to go or you’re very fast on the downhill till you hit a tree.
- The Speed of a tire should be a understood as a combination of rolling resistance and weight. The rolling resistance “…is the force resisting the motion…” (Wikipedia). This force needs to be overcome continuously. The weight is mainly a drag factor on climbs and while accelerating. Which is pretty much what mountain biking is all about.
- Toughness is the ability of the tire to withstand the elements mainly in the form of sharp objects like rocks or thorns. A robust tire protects better against punctures, pinch flats and sidewall cuts. Robust tires are also less prone to squirming which all rides to expose the tire to more lateral force (e.g. on downhills).
- Durability is the ability to maintain the performance of the tire during an ideally long lifetime. Main factor is rubber abrasion, but there are also lizard-like tires which drop body parts (knobs) when in danger.
- Comfort is the ability to cushion the ride and provide a feeling of safety and control. It’s mainly the ability to mould to the ground while smoothing out bumps and providing the feeling of being connected to the ground without squirming.
Components of a tire which determine the performance of a tire:
Additional parameters (will be covered in greater detail soon…)
- Wheel Size. Diameters of tires range from 26″, over 27.5″ (650b) to 29″.
- Tire Volume/Width. Typical tire width ranges from 1.9″ to 2.5″. “Plus” tires go up to 3″ and tires for fat bikes even to 4″.