Mountain Biking for Dummies - TIRES

Everything that’s been said before, be it a general comment about frame type or what type of suspension to look for, doesn’t matter.  Yes, I said that.  All thousands of words I’ve already written on mountain biking are relatively useless if you don’t get the fourth part correct.  What IS that mystical fourth part, you ask? Well, it’s tire selection.

Why are tires so important?

That’s a good question, and it’s an easy one to overlook and take for granted. You can have the nicest $10,000 mountain bike with extremely high level components, suspension, and frame and yet be totally lost if you’ve got the wrong tire for the job you’re doing. Conversely, you can have an extremely beginner bicycle but if your tire is paired perfectly to your trail and riding style you can easily drop your buddy on the ultra expensive machine and, let’s be honest, who doesn’t like dropping their buddies every now and then??

I am, admittedly, being a bit dramatic (I tend to do that in these types of things) but that is ONLY to make a point! Any bike you buy will likely come with tires that are simply “pretty good” at most things.  They’ll do a fine job of accommodating your needs and desires.  That being said, as you become more and more familiar with your comfort level and appropriate riding skills you may find yourself wanting to explore tire choice and selection a bit more.  It’s different than road cycling, where tires are definitely important in terms of how fast you go or how many punctures you get but play very little role in how fast you can take a turn or how quickly you can slow down or get back up to speed.

Mountain bike tires essentially fall into two categories: tubed and tubeless (if we’re getting nitpicky you can also find tubular mountain bike tires, but those are not very common at all).  Tubed tires will be familiar to everyone that is familiar with bikes; there is an inner tube that is inflated and holds the tire’s shape.  TubeLESS tires have no inner tube; the tire hooks into the wheel’s rim and through a combination of specific rim tape and liquid sealant, stays inflated and rigid.

Tubed tires and tubes in general are the easiest from an upkeep standpoint.  If you get a flat you simply replace the tube. There is no sealant to refill and there is no difficulty in getting the tire to “attach” and inflate the first time you install it (which can be difficult with tubeless tires). The downside to a tubed system is that it generally weighs more and you run a higher risk of pinch flatting (this is what happens when you go over some sort of bump and the tire/tube compresses so much that the tire pinches the tube between the metal rim and the tire which, in turn, punctures it).  This is not particularly common in road cycling but, as you can imagine, is more common on trails as there are far more obstacles to roll over with your tires.  

Tubeless tires are generally considered preferable, as you eliminate the tube and any risk of pinch flatting.  You can run the tires at lower psi, which increases your available traction (the tire “grips” surfaces better) and the system usually weighs less.  There is less risk of flats as well, as the liquid sealant running around in the tire (about 2 ounces worth) rushes to the site of any small cut or puncture (think of the sealant as platelets in your blood!) and seals the hole and you can continue riding and may never even know you got a puncture.  Obviously, some cuts or punctures will be too big for the sealant and you should always run with a flat repair kit.  Installing a tube into a flat tubeless tire is very easy and is what almost everybody carries with them while riding (whether riding tubed tires or tubeless tires).

Every single mountain bike you buy, however, will come with tubes (as far as I’m aware, unless the shop has set it up tubeless out of the box). Most mountain bikes that are above $1000 or so are “tubeless” ready and you can easily ask your shop to set it up that way once you are comfortable with the idea.  You merely have to buy sealant and, potentially, rim tape; neither of these will set you back more than $30-$50 (including installation).

Tread types are very important when it comes to confidence and technical skill, so it’s important to learn some about what makes certain tires more suitable for certain conditions and different environments.

Tire tread is essentially composed of three elements: center knobs, transition knobs, and side knobs.  Each of those plays a pretty specific role in maintaining traction, which is a tire’s ultimate goal. If you are riding in loose soil you want deeper penetration. If it’s harder soil (think desert conditions) you don’t need as much penetration. So the SIZE of the knobs is important insofar as it relates to the density of your surface.

The number of knobs is also related to surface conditions; the more knobs you have the less each individual knob will penetrate the soil, which is what leads to traction.  So harder soil means you can run more knobs in your tread and maintain adequate grip. Looser soil means fewer knobs, each of which will penetrate the soil more.

The placement of those knobs is also important.  Looser soil means you generally need to have a decent amount of space between the knobs so that once the soil has been penetrated it has channels to run through, so to speak.  Loose OVER hardpack (commonly found in the southwest) generally demands this type of tire.  Nice channels that run between your side knobs and center knobs, but the center knobs can be more dense (i.e. more of them) while the side and/or transition knobs can be less dense but perhaps bigger.

Interestingly, riding style also plays a role in tire selection.  Some cyclists LEAN the bike quite a bit through turns and as a consequence they don’t really need transition knobs as they go from “upright” to leaned over and get plenty of traction and control in that leaned position.  So more “aggressive” riders tend to prefer a tire with bigger channels.  Riders who don’t lean the bike aggressively (which is most riders) find tires like that to have a sudden cliff in terms of traction.  They don’t lean the bike aggressively and therefore never really contact the side knobs, so the bigger channel robs them of confidence and traction in the corners.

Ultimately, tire choice is about experimentation.  Finding a good front/rear combination that works for you and your riding style/location is often trial and error.  Knowing certain things about tires themselves, however, can help you make more informed decisions.  I’ll give you my own personal example here:

In Tucson, leaning your bike (i.e. making aggressive turns) is difficult because it feels like there is  cactus around every corner.  So if I lean, I get spiked.  As a consequence, I do not turn or lean the bike nearly as aggressively as I did back on the east coast. So my tire choice in that respect is different.  The soil conditions here in Tucson are also wildly different than North Carolina.  The soil there was grippy, generally, and had a bit of give to it.  The soil here is extremely hard underneath a very loose layer of rock and sand.  So tire choice is different in that respect as well.  Furthermore, all of the rocks here are out to kill you and your bike.  So my tire choice needs to be a bit more durable (extra puncture layers or sidewall protection) if I want the tires to last more than a couple of weeks’ worth of riding.

So, it’s important to experiment and figure out what works best for you, where you live, and how you ride! But use some of these keys to help you make your decision!