What Are 650b Tires? An Explainer on 27.5 in Wheels for Gravel and Mountain Bike

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Riding a bike has been both a pastime and an easy mode of transportation for people for as long as we can remember. But what people who are not bike enthusiasts don’t know is that different bikes offer different advantages depending on the surface. Mountain bikes, for example, are best used on an off-beaten path where stability and smoothness are needed. With the comfort of riders in mind, the sizes of bike tires have been diversified. Historically, most mountain bikes use 26” bike diameters, but recent innovations gave rise to the popularity of wider 650B tires.


What are 650b Tires?

Kirk Pacenti introduced the first 650B tire in 2008.

650b tires (ISO-584mm), also referred to as the modern mountain bike tire, are mountain bike tires with an outside diameter of 27.5”. It is a compromise between the original 26” and the newly released larger size 29”. It provides the best of both worlds. From the stiffness, speed, and agility of 26” to the smoothness of ride and better grip of the 29” tire – you have it all.

The name 650B comes from the French nomenclature where the number 650 denotes the approximate diameter of the tire. The letter B, on the other hand, corresponds to the tire’s width. For comparison, a 700C tire has a larger diameter and width than a 650B tire.

What to Consider When Choosing a Tire?

Type of Tire

Tires are categorized as clincher, tubeless or tubular type.

Clincher Tire

Clincher tires are the most common types of tires. It has an open bottom and uses a bead of hard rubber to clinch to the rim of the wheel. Inside a clincher is a tube that holds the air. It creates pressure that gives firmness to the tire. Having this separate inner tube, a clincher tire can be easily replaced, when you get a flat. Clincher tires are also called wire bead tires. The beads use wires that clinch to the rim of the wheel.

A folding tire is a special type of clincher tire that uses a Kevlar strand instead of a wire. This gives rise to higher flexibility and can easily be folded, thus, the name.

Tubular Tire

Tubular tires look like clincher tires on the rim, but have no inner tube. Unlike the clincher tire that has an open bottom, a tubular tire has no open part. The tire is stitched around an inner tube that makes it seem to be a one-piece tire.

The tire is then glued directly to the rim of a tubular wheel since they tend to move when not glued in place. Usually, tubular tires are lighter than clincher tires. This makes them accelerate faster. On the other hand, tubular tires are usually more expensive and harder to maintain.

Tubeless Tire

Tubeless tires are basically like clincher tires but without the inner tube. It is a relatively new type of tire. It allows operation at a lower tire pressure. A liquid sealant helps seal the tire and avoid the risk of pinch flats. One big advantage of a tubeless tire is that it is easier to maintain. However, it is not as readily available compared to the clincher and tubular types.

Tire Tread

For a more comfortable ride, tire threads can vary with depth and pattern depending on the surface you intend to use your bike.

Slick tires have smoother patterns. These are useful for smooth surfaces because of its larger contact with the road. Road bikes often use these tires. A smoother center pattern gives a faster, smoother ride on the road. Outer thread helps better movement on small debris or water. This type of tire is also suitable on hard-packed gravel surfaces.

Knobby tires are used on bikes intended for rougher surfaces such as loose gravel, mud, and dirt. Mountain bikes often use these tires that have a higher thread depth.

Generally, tires that have more tightly packed thread are useful on dirt or gravel.

A lower depth center pattern helps give a much faster straight-line speed. For a more adventurous, aggressive ride, deeper threads offer more grip and slip resistance.

Tire Casings

The tire casing is a layer beneath the tire tread. It is the body and structure of the tire. It consists of a single or multiple layers of woven cloth material. Tire casings are described by how many threads they contain per inch or TPI. They can be integrated with soft plastics or hard rubber inserts to reinforce the tire for better performance.

Thickness and weight are the things to consider when choosing the right tire casing. Thicker casings provide more protection to the sidewalls and center thread. It also gives an added resistance to cuts and punctures. However, added layers, in turn, make the casing heavier, which results in a lower acceleration.


A mixture of organic and inorganic polymers makes up the material for a tire. The different components of the rubber compounds contribute to the tire’s texture and rigidity.

Compare a rubber shoe and a wooden sandal. The rubber shoe grips more on the floor than the wooden sandal. It prevents you from slipping, but sliding is almost impossible. This is also true when comparing softer rubber compounds to their harder counterparts. For a better grip between the surface and the tire, softer rubber compounds are used on knobs but would create move resistance on movement or rolling.

To compensate for this, creators usually construct tires with softer rubber compounds on the side knobs for better cornering grip but harder rubber compounds on the center knobs for less rolling resistance and high speed.

Tire Width

In connection with tire diameter, a wider tire creates a larger contact surface to the ground. This in turn allows more grip or traction but also more rolling resistance. This gives you a safer ride. However, it is not suitable for racing or when traveling on smooth surfaces.

On the contrary, smaller diameter tires offer less rolling resistance but also a lesser grip. Mountain bike widths range between 1.9” to almost 5”, depending on use and preference.

What are the Pros and Cons of Using a 650b Tire?

When 650b tires were first introduced, the goal was to make it a compromise between the smaller 26” and the larger 29” diameter tires. With its 27.5’ diameter, it sits right in the middle of the two and is expected to have characteristics from the other two sizes. Although the 650b tires were prompted to have the best of both worlds, the midsize tire also has some disadvantages of its own.


With its larger diameter, the 27.5” tire provides a higher top speed than the 26″ tires. Meaning, with the same amount of pedaling, 650b tires travel a longer distance. It also offers faster acceleration and quicker reaction times than bikes with 29” tires.

It also provides better traction or grip than a 26” tire since it has a larger contact surface with the ground. 650b tires are also recommended for riders who want bigger bikes, but are not as comfortable with a 29”.

Overall, the larger wheels have a higher air volume that gives more comfort to the rider. It does not allow too much vibration passed on to the rider when traveling on a rough, irregular surface.


As top speed comes with diameter, 27.5” tires have slower top speed compared to 29” diameter tires. On the other hand, it has a slower acceleration compared to a smaller 26”. With its larger diameter, 29” tires still have better traction than a 27.5”.

A 27.5” tire doesn’t run as smooth as a 29”, especially on rougher trails.

Examples of 650B Tires

Just getting started learning about 650B bike tires? Here are some examples you can look at online along with advantages that are specific to each product.

Vittoria Terreno Zero G2.0

vittoria terreno zero g2.0 650b bike tire isolated on white background

The Vittoria Terreno Zero’s design is Corsa-inspired with a noticeable smooth center thread and hexagonal side threads. The smooth center tread allows it to roll faster on paved and hard-packed gravel surfaces. The hexagonal side thread, or “scales,” allows reliable grips through corners and when braking.

This Vittoria product uses 3C technology wherein 3 separate compounds are used in the same tread. It also uses a Graphene 2.0 (G2.0) rubber compound that provides the tire an increased performance, especially on speed and wet grip. It also offers higher resistance to puncture and at the same time maintains durability.


  • Compound: 3C Graphene 2.0
  • Size: 650B x1.75
  • Tire Type: Tubeless-Ready/Clincher
  • Surface: Gravel
  • TPI: 120
  • Bead Type: Foldable

Pro: Less rolling resistance on paved and hard-packed gravel surfaces.

Con: Smooth thread does not offer much grip when the road becomes muddy.

Maxxis Re-Fuse MaxxShield Gravel Tire

maxxis re fuse maxxshield gravel tire isolated on white background

Available in widths of 2 inches and 47mm, the high-volume Maxxis Re-Fuse MaxxShield Gravel Tire offers high contact to the surface. The diamond-knurled slick design of the thread provides a better grip and traction but with less rolling resistance. With the higher air volume, the tires give a comfortable feeling for the rider due to less vibration.

Thanks to the added bead-to-bead protection technology of these 650B tires, cuts and punctures are not as worrisome due to higher resistance. So whenever you take your bike, you would have less worry about running flat.


  • Compound: Dual Compound Rubber
  • Size: 27.5”x2.0, 650Bx47mm
  • Tire Type: Tubeless Ready
  • Surface: Gravel
  • TPI: 60
  • Bead Type: Foldable

Pro: High puncture resistance, comfortable due to high-air volume and good grip on drier roads but rolls well.

Con: Lesser grip on muddy roads.

Maxxis Aggressor Folding Dual Compound EXO/TR Tire

maxxis aggressor folding dual compound exo/tr tire

Loyal to its name, this aggressive tire is aimed to offer high-performance for aggressive riders, especially on tougher terrains. This great product from Maxxis, the Maxxis Aggressor Folding Dual Compound Tire has more spread-out knobs that increase tire versatility with different surfaces and conditions. The knob pattern creates extra gripping edges without compromising the rolling efficiency due to the lower profile center tread design. The side knobs are further reinforced to ensure stability when cornering at speed.

With its EXO feature, the Aggressor has an added layer to the sidewall that makes an extremely cut and abrasion-resistant material. Having the necessary grip, high top speed but less rolling resistance, this bike tire is suitable for riders that like challenges and risks.

Moreover, the DoubleDown feature offers two 120 TPI casing layers for better strength and protection at a lower weight. The characteristics of the Maxxis Aggressor make it very suitable as a rear tire.


  • Compound: Dual Compound Rubber
  • Size: 27.5”x2.3, 27.5”x2.5
  • Tire Type: Tubeless Ready
  • Surface: Gravel, Mountain
  • TPI: 120
  • Bead Type: Foldable

Pro: Offers good brake and cornering traction on various rough terrains while maintaining good rolling speed.

Con: Shorter knobs may not be helpful on wet, muddy surfaces.

WTB Resolute TCS Light Fast Rolling Tire

wtb resolute tcs light fast rolling tire isolated on white background

The simple yet well thought square patterns of the WTB Resolute make it a very versatile gravel tire. It is perfect for any weather. The widely-spaced knobs create consistent traction while being able to part mud for ease of riding.

It features an SG2 Puncture Protection that provides a bead-to-bead coverage for high cuts and slash-resistance. The use of lightweight nylon makes the tire weigh lighter, which gives it a high speed. The square thread pattern also gives the tire a classic look.


  • Compound: Dual Compound Rubber
  • Size: 27.5”x42mm
  • Tire Type: Tubeless Ready
  • Surface: Gravel, Road
  • TPI: 120
  • Bead Type: Foldable

Pro: Good grip, versatile in almost all situations.

Con: Low air volume due to smaller width reducing comfort.

Kenda Flintridge Pro

kenda flintridge pro 650b bike tire isolated on white background

The Kenda Flintridge Pro got its name from the sharp jagged rocks of the hills of Kansas. This brand of 650B tires boasts a fast-rolling speed due to its smooth center tread pattern that makes it suitable for paved and hard-packed grounds. On the contrary, the shoulder knob designs offer a tight grip and traction on loose rocks and even mud.

The Kenda Flintridge Pro features a KSCT casing that is ready for a tubeless conversion. The casing also reinforces the sidewalls of the tire with a woven shield so that slashes and abrasions are prevented.


  • Compound: DTC Dual Thread Compound
  • Size: 27.5”x45mm
  • Tire Type: Tubeless-Ready/Clincher
  • Surface: Gravel
  • TPI: 120
  • Bead Type: Foldable

Pro: Easy tubeless set-up, rolls well especially on hard-packed surfaces.

Con: A bit heavy at more than 500g.

Panaracer GravelKing SK

panaracer gravelking sk 650b bike tire isolated on white background

If you want an adventurous ride but want 650B tires that give you comfort when thrown on a rocky surface, then Panaracer GravelKing SK is a good choice for you. The tightly packed, square center patterns promote reduced vibration during rides.

Aside from that, the low profile center thread creates a larger surface contact for a better grip. But still, it keeps a fast-rolling performance, especially on paved and hard surfaces.

The GravelKing features a ZSG (Zero Slip Grip) natural rubber compound, which provides consistent performance even at various temperatures. It also has a higher 126 TPI thanks to its Advanced Extra Alpha casing that gives extra protection and resistance from cuts and abrasions.


  • Compound: ZSG natural rubber compound
  • Size: 27.5”x1.9
  • Tire Type: Tubeless-Ready/Clincher
  • Surface: Gravel
  • TPI: 120
  • Bead Type: Foldable

Pro: Fast-rolling at a reasonable good price, highly resistant to abrasions.

Con: The side knobs do not offer great cornering grip.


No matter what type of road you traverse – whether paved or trodden roads, or muddy, rocky less-used paths – mountain bikes are a suitable vehicle to hop on.

Choosing the right tire greatly depends on the rider’s preference. Would you like a tire that can make you ride faster along paved or hard surfaces or have a tire that allows you to feel safe when on a bumpy, more adventurous ride?

Although it doesn’t mean that these middle-sized tires are perfect on all occasions, the 650B tires live up to their goal of giving the best of both 26” and 29” worlds.

Last Updated on May 29, 2023 by Danijel Cakalic

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