When you first start mountain biking the tyres fitted on your bike should be fine. Just keep them properly inflated and from time to time, check that they are not worn or damaged. (See also Maintenance). However, as you spend more time riding and become more involved in the sport you will realize that choosing the correct tyre can make a big difference to your performance and allow you to get more out of your riding.
The tyre market is massive with new designs constantly arriving in the shops, but there are basically five types of tyre for different purposes:
Choosing the correct tyre can make a big difference to your performance
- Semi slick
All you have to do is choose the right ones for you and your preferred riding terrain and style. But to make life a little more interesting, tyres also come in different sizes and different qualities and they can also be specific to either the front or rear wheel (and some are even available in a choice of colours too!).
Tyres for mountain bikes are measured in inches. Their nominal diameter is 26" but the width (or depth) can vary from 1" to 3"
Tyres for mountain bikes are measured in inches. Their nominal diameter is 26" but the width (or depth) can vary from 1" to 3". But beware as the sizing does vary from one brand to another and tyres marked 26 x 2" from different manufacturers may be very different sizes when you fit them on your rims!
To add to the confusion, there are even different rim diameters which purport to be 26" too! Check the additional figures on the sidewall of your original tyre to make sure the new tyre will fit your rims. The important figures to look are two digits followed by three digits e.g. 47-559. This is the ETRTO marking (European Tyre and Rim Technical Organization). The first number (47) is the nominal section width of the tyre, in millimetres and the second number (559) is the inside diameter of the tyre (also in millimetres), which must match the rim size. You can fit tyres of different width onto various rims but if the rim size is wrong, the tyre will not fit!
The ETRTO number is 57-599
Tyres prices vary considerably. In part this is due to the manufacturers' individual reputation but mostly it is because of the quality of manufacture and materials used. Top quality tyres have more threads per inch (TPI) in the tyre casing than the budget models. With more TPI the tyre is stronger, less prone to punctures and provides a better, more 'plush' and responsive, ride. For example, top of the range Michelin tyres have 127 TPI and their budget tires have just 33 TPI.
Budget tyres have a steel bead (the inside edge of the tyre that hooks onto the rim and holds the tyre in place) whereas more expensive tyres use Kevlar which is much lighter, yet equally strong and can make fitting and removal much easier.
Some mountain bike tyres are designed specifically for the front or rear wheels. The front tyre is primarily concerned with steering and braking. The job of the rear tyre is to assist with stability and drive. Further, some tyres have tread patterns that are 'direction specific' for better traction - usually indicated by an arrow on the side of the tyre.
The most common tyres, fitted on the vast majority of new mountain bikes. They have an open (or studded) tyre pattern that works well in all conditions from dust to mud. The tread pattern is not overly aggressive to allow the tyre to roll relatively on all sorts of surfaces from forest tracks to tarmac. Most general tyres are 26X 1.9" or 26 x 2" - not too huge but still large enough to absorb most impacts and be reasonably robust. Such tyres are a good compromise choice for most conditions and there is a wide choice of style and prices. However, they are not ideal in all conditions and usually they are heavy with a low TPI count.
Michelin DH Mud 3 tyre
As mountain bikers you expect to ride in the mud now and then - especially in the UK! When conditions are really bad you will benefit from having a tyre specifically designed for muddy conditions. These have a very aggressive with widely a spaced stud pattern for improved traction and less clogging up of the tyre. Mud tires are often smaller in width, 1.5"-1.9", to cut through the mud better and avoid clogging up the frame especially next to the brakes and the chain stays when riding in glutinous conditions. Note however, that specific mud tyres don't handle so well on other surfaces and they can feel slow, particularly on tarmac.
If downhill riding is your 'thing' then you need to use 'downhill' tyres. These are also larger in width than cross country tyres, can be run at slightly lower pressures for better grip and to absorb larger impacts without puncturing and they have an open and aggressive tread for maximum grip and improved stability for faster downhill riding. Due to their wide section and gnarly treads, downhill tyres feel too sluggish and heavy for cross-country riding. Their large size also means that frame clearance is reduced and unless you have a specific downhill bike, they will soon clog the bike in wet conditions.
Slick tyres, with little or no tread pattern, are similar to tires on a road bike and they are much faster and easier to ride on the road than regular mountain-bike tyres. Except for easy trails, they are less suitable for off-road use as they will offer limited grip and their narrow cross-section (1.0"-1.5") makes them more susceptible to puncture on rocks. However, on the road their rolling resistance is considerably less than any off-road tyre, and such tyres are the ideal choice for street use or touring on the roads - provided you don't mind your bike looking 'gappy' if it's originally been built with wide clearances for mud.
Panaracer Mach Semi slick tyre
As the name implies, these are a compromise between the slick tyres designed for road use and off-road tyres for trail use. Usually such tyres have a heavy file tread pattern in the centre, with knobbly studs on the outside edges for help when cornering in off-road situations. Other patterns exist but the key feature is that any tread pattern is fairly shallow. Semi slicks are usually a middling size, 1.5"-1.8". Semi slicks are a good compromise if your riding regularly involves both road and trail (such as Trailquest competitions, or canal towpath riding) but they are never ideal either on road or off road.