MTB Tire Selection Fundamentals, Tread, Sidewall, Compound, Profile Shape
Choosing the best MTB tire requires understanding basic fundamentals of Tread Pattern, Sidewall, Compound and Profile Shape as they apply to your terrain and riding style.
A couple quick considerations for this writeup:
GROUND CONDITIONS will affect tire personality, ie ultra-hard pack versus tacky hero dirt versus mud will have different “fastest” patterns based on being able to generate traction.
For this breakdown let’s use basic loose over hard pack conditions as a reference point.
WEIGHT matters – more to some, less to others but it matters.
Some oversimplified science: The amount of force it requires to accelerate a wheel is affected by its moment of inertia. Moment of inertia, oversimplified, is a product of Mass x Radius Squared (i=MR²).
Larger lugs weigh more, and rubber isn’t particularly light. On a mountain bike wheel we are placing a decent amount of mass at the edge of a radius, basically a 720g tire will have a moment of inertia .73 lower than a 990g tire.
Of course if the tire won’t stick, think of a racecar with slicks versus rain tires in the wet, it doesn’t matter how light it is so riders must balance the appropriate tires for their riding conditions.
It’s easy to understand tread patterns’ personality if you break it down into three areas.
The center section of a tire is responsible for balancing acceleration, braking and rolling efficiency.
Smaller and tighter lugs are faster rolling in most conditions.
Taller lugs with greater spacing are better suited to claw into terrain for grip, however the improved traction will come at the cost of some rolling efficiency and acceleration.
Spacing is important to move debris and accommodate for “pack” in sticky conditions. Really tight spacing will pack more easily which turns your tread into a slick and compromises traction.
Cornering lugs are located on the edge of a tread pattern. Available grip from a cornering lug is based on size, stiffness, and location.
Aggressive riders confident at higher lean angles often appreciate larger, more supportive, higher grip lugs.
High skill set riders may choose smaller cornering tread patterns for improved rolling speeds while relying on technique to “override” a tire’s grip.
XC or trail riders vary – some prefer the lighter, smaller lugs while others prefer the confidence of more aggressive cornering shapes.
Cornering tread is especially important on a front tire to control the feeling of “slide” or losing the front end. A lot of riders are able to override a rear tire (allowing it a bit of give or slide) there are far fewer who are comfortable and confident in consistent two wheel drifts!
Transition tread is located between the center and cornering sections of a tire. The amount of transition knob versus space, or channel, affects speed, rolling resistance and grip while transitioning from vertical to full lean on the side knobs.
Riders who turn with less substantial lean angles find additional transition knobs confident as it minimizes slip. Those who quickly dive from center to cornering tread require less transition knobs typically.
Various sidewall technologies are available to balance stiffness, resistance to damage and weight. Each manufacturer has coined their own nomenclature, so we will reference Maxxis’ for ease of conversation.
Skinwall tires are the lightest available and often seen on XC race setups.
EXO sidewalls are reinforced, which offer excellent support for larger riders as well as more resistance to tears or punctures. This mid-level protection is the most popular for a wide variety of riders. From aggressive enduro riding to trail adventure riding the small weight penalty is often overlooked for the overall performance gains. Think about this – how much faster will you really be and does that balance out if you flat and have to deal with it.
Double Down sidewalls are the newest offering from Maxxis. This technology is essentially a folding downhill carcass offering the ultimate in protection from abuse and sharp terrain. Double Down is becoming more popular with Enduro racers, particularly as a front tire, thanks to its ability to hold air through incredible abuse.
Mountain Bike Tires are available in a variety of compound combinations. Different levels of “tackiness” are available from various durometers of rubber.
Typically a lower durometer, or softer rubber, will have additional grip with less resistance to wear. Harder durometer rubber has improved service life at the cost of some degree of traction.
Many tire manufacturers offer multi-compound offerings with a harder, faster center section and softer, more compliant cornering knobs.
It is important to pair the right tire with the right rim width for your riding. Modern MTB rims have settled into the 27mm to 35mm range for most riders. Manipulating the rim / tire interface sizing produces different volume capacity as well as overall tire profile shape.
Riding on the narrower end of the spectrum it is important to ensure cornering lugs are not rolled too far over as they require higher lean angles to engage.
Wider rims sizes have been accommodated with technologies such as WT from Maxxis. WT tires feature cornering tread is specific to wider rims with higher volume setups. Some tires may suffer cornering lugs which are too vertical that don’t grip at high lean angles when installed on wider rims.
Most 2.25-2.6” tires are rideable on the 27-35mm rim standards, however if you’ve noted cornering problems on a tire with appropriate cornering lugs it’s worth a look at how they mount.
Image 1 illustrates the shape expected when a tire is mounted on too wide of a rim for the tread shape. Comparing the outer edge of the tire to the cornering lugs note little or no overlap. Expect a tire that will not like to corner at aggressive lean angles.
Image 2 is a good shape for most riders. The lug overlap is clear, however the lug isn’t rolled so far over that it will slip in normal cornering.
Image 3 is less common – but if the cornering lug is too far past the sidewall it requires a TON of lean angle when cornering to engage.
COMMON DIFFERENCES FRONT TO REAR
Here are some basics you may come across on MTB setups.
Many riders prefer a more aggressive front with a faster rolling rear tire. Front tires are commonly wider than rear options as well – again balancing grip and speed.
Some riders prefer a slightly more resilient front sidewall while other setups are equal sidewall technologies front and rear. It would be unusual to have a less supportive sidewall in the front compared to the rear tire although some race conditions may call for it.
Standard MTB setups most often feature a front tire of equal, or lower or stickier, durometer compared to the rear. This helps with grip and wear as rear tires tend to wear faster than fronts.
BikeCo carries the best tires on the market from Maxxis, Onza, WTB and Schwalbe. Our expert staff is here via chat, phone, or email to help you dial in your purchase.
A word to the wise on tires – there are many, many variations of popular tires out on the market. Some are great tire options like BikeCo offers and some are cheap, look alike knock offs! Be particularly wary of sidewalls and compound. I have seen a $25 version of a $75 tire in a big sporting good dealer and was shocked when I nearly put my thumb through the sidewall as well as the tread rubber being rock hard. Not here to frighten riders of it, simply educate them that these exist…