Mountain Bike Tires 101

Tires 101

While it might seem like they’re pretty much all the same, the fact is that the right tire can be the difference between having a very good time and a pretty bad time on your bike.

Bad tires — or even “good” tires that aren’t the right choice for the kind of riding you’re doing — can have you skittering down the trail out of control (while praying you avoid your third flat tire of the day), as opposed to achieving a zen-like flow, railing corners, cleaning climbs, and making it back to the car without needing a pump.

And no matter how nice your bike is, the wrong tires can make a great bike ride poorly, while the right tires can make any bike ride that much better.

So what do you need to know about tires, and how do you figure out which ones will work best for you given how and where you ride?

Before you go spend your money on some random piece of rubber, there are a lot of concepts and features that are good to understand. And in this article, we’ll walk through some of the most important things to look for, then offer some specific recommendations based on different priorities (durability, grip, etc.) and scenarios.

There are five basic elements to consider when shopping for a tire: tire size, tread pattern, casing & construction, rubber compound, and bead type. We’ll get into each of those, and cut through the jargon and talk about what each company’s marketing terms actually mean.

There’s a lot of information in here, so you can use the jump links below to skip around as you like.

Index

1) Tire Size (page 1)
2) Tread Pattern
3) Casing and Construction
4) Rubber Compounds & Bead Type
5) Specific Tire Recommendations

Most tires come in a few different sizes, casings, rubber compounds, and bead types. We’ll help you navigate those options here, but you’ll also want to check out our in-depth tire reviews for longer discussions of specific tires.

Basic Elements of a Bike Tire

Now just before we get into the meat and potatoes, here’s a handy graphic from Maxxis that gives us the basic elements of any bike tire — the tread, the casing, the sidewall, the bead — and some tires will have reinforcements to help with puncture protection or other durability concerns. We’ll talk about all of these below.

Tire Size — Diameter & Width

This one’s pretty obvious, but you’re going to need a tire that’s the right diameter for your wheel, and that’s the right width for the type of riding you want to do. So let’s talk about diameter and width:

Diameter

Wheel diameter measurements are most commonly expressed in inches: 26”, 27.5”, and 29”. Those same dimensions are sometimes expressed using the French sizing system – a 27.5” wheel is the same as a 650b wheel, and a 29” wheel is the same as a 700c wheel.

A Side Note on ISO and ETRTO Sizes

Sometimes, you’ll see tire sizes expressed as a string of numbers; something like 60-622. That’s an ISO / ETRTO size designation that gives both the width (60 mm) and the diameter (622 mm). The International Standardization Organization (ISO) has superseded the European Tire and Rim Technical Organization (ETRTO), but both organizations are still referenced sometimes.

Both the width and the diameter are measured in millimeters. In our 60-622 example, 60 mm would be the width of the tire at the widest point (which, in real life, will vary a bit depending on the width of the rim it’s mounted to). 622 mm would be the diameter of the bead seat of the rim. Expressed in their ISO form – 26” wheels are ISO 559 mm, 27.5” wheels are ISO 584 mm, and 29” wheels are ISO 622 mm.

Regardless of the naming designation that you use, when buying tires you just need to buy the appropriate tire to fit your rim.

Width

Most tires come in multiple widths, and this can be the trickier decision.

• Knobby tires for “regular” mountain bikes range from around 1.8” in width to around 2.6”.
• Plus bikes (i.e. 27.5+) usually have tires around 2.8” to 3.0” wide.
• Fat bikes have tires wider than that, up to around 5” wide.

The delineations between where regular tires turn into “plus” tires, and where plus tires turn into “fat” bike tires are a little vague, but ultimately, it’s just semantics.

People have been arguing about the pros and cons of various tire widths for many, many years. I’m not going to fully open up that can of worms here, but there are a few basic considerations when deciding on tire width:

Take a look at your frame and fork clearance. Any given frame or fork is going to have a maximum tire width that it’ll accommodate. If you go too wide, it’s going to rub. On a fork, if you run a tire that’s too big, even if it doesn’t rub you run the risk of the tire hitting the crown on a hard bottom out. That’s a good way to lose some teeth.

Also factor in mud clearance. If you ride in a muddy area and cram the largest possible tire into your frame, things might get gummed up.

Look at your rim width; ideally, the measurement you want is the internal width of the rim. If you put a wide tire on a narrow rim, the tire won’t have good cornering support and might feel squirmy in corners. You’ll have to run higher pressures to counter that. Conversely, if you put a narrow tire on a super wide rim, the bead might not properly engage, the sidewall is more prone to damage, and the tire will have a very square profile that can ride a bit weird.

For the majority of mountain bikes out there, internal rim widths are going to be in the 18-30mm ballpark (which translates to around 21-33mm external widths). If you already have firmly held opinions on tire widths, feel free to ignore the next sentence. But if you’re lost on tire width and don’t even know where to start, I’m of the opinion that 2.1” tires work best on 18-22mm rims, 2.3” tires work best on 23-27mm rims, and 2.5” tires work best on 28-30mm rims, up to around 35 mm. Beyond 35 mm, you’re generally into “plus” tire territory.

Wider tires tend to be heavier.

Narrower tires tend to provide less traction.

In some situations, wider tires roll slower, but that’s not always the case.

Some companies are coming out with tires that are specifically designed to work well on wider rims. For example, the Maxxis Wide Trail series of tires are designed to work well on rims that are over 30 mm wide (internal).

A Note on Front vs. Rear

Plenty of people run the same width tires front and rear. Plenty of people put a wider tire in the front. Both options have their pros and cons, but really, some bikes and riding styles tend to work better with matched tires, and some work better with a wider tire in the front. Generally speaking, the reason for a wider tire in the front is to gain a bit of cornering traction so that the rear tire will usually be the first to break free in a corner. When the rear tire is the first to break free, you get a little bit of oversteer, which can be desirable. But when the front tire is the first to break free, you tend to crash, which is undesirable. For that same reason, you generally don’t want a larger tire in the rear.

NEXT: Tread Pattern