TPU inner tubes are gaining attention as the third force in bicycle tires. We summarize its features, advantages and disadvantages of using it on Road bikes and MTBs, and major manufacturers.
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No Strict “Differences or Standards” between Road and Gravel
There are no clear standards for gravel bikes, which are treated as a genre of road bikes.
Gravel bikes are characterized by the following two features
- performance on rough terrain
- performance on paved roads
A road bike that has a balance of both of these characteristics is often called a gravel bike, and there is no clear distinction between “drop handlebars for road bikes” and “suspension for MTBs”.
In addition, there is no clear standard for “performance on rough roads,” so to take it to the extreme, if a manufacturer says “it is a gravel bike,” it can be classified as a gravel bike.
In the first place, there are many areas where the classification of bicycles is not clear, but the criteria for gravel bikes are more ambiguous, and because of the unique characteristics of gravel bikes, it is more difficult to understand them.
One clear way to tell if a bike is equipped with gravel composites
One of the clearest ways to determine if a bike is a gravel bike is if it is equipped with gravel components.
Currently, the three major bicycle component manufacturers, Shimano, Campagnolo, and Sram, all release components for gravel. Shimano’s GRX, Campagnolo’s EKAR, and Sram’s XPLR are all gravel components.
Road bikes equipped with these components are definitely considered “gravel bikes”. For example, MERIDA’s gravel series “SILEX” is equipped with Shimano GRX.
Gravel Bike" even if not equipped with gravel components
On the other hand, if you look at what complete bike manufacturers call “gravel bikes,” you will find that they are not necessarily equipped with gravel components.
For example, NESTO’s gravel bike “GAVEL” and FUJI’s “JARI 1.7” are equipped with Shimano’s entry-level SORA R3000 series components, while FELT’s gravel bike “BROAM” is the top-of-the-line grade, equipped with a mix of GRX RX810 series FELT’s gravel bike “BROAM” is equipped with a mix of GRX RX810 series and RX600 series composites, but other models are equipped with TIAGRA and CLARIS composites.
The RADAR EXPERT, a gravel bike from the American off-road bicycle brand BREEZER, has a mixed component configuration of Shimano’s DEORE for MTB, despite its drop handlebars.
How to identify a gravel bike other than its components
Equipped with gravel tires
One of the main characteristics of gravel bikes that distinguishes them from road bikes is that they are equipped with thick gravel tires. This is because gravel bikes are designed to be ridden on unpaved roads, so they need larger tires to catch the road surface well on unpaved roads.
While 25C size is the most common size for road bikes, most gravel bikes are equipped with larger tires, such as 30C or larger, or even 38C depending on the model.
In this sense, if the bike looks like a road bike but is equipped with thicker tires of 35C or more, it can be considered suitable for gravel use as well, even if it is not called a “gravel bike.
The bike is equipped with disc brakes.
Most gravel bikes, which are designed to be ridden on gravel and other rough roads, are equipped with disc brakes to avoid mud and sand on the rims and shoes, which can reduce braking power and damage the brakes and wheels.
This is partly because conventional rim brakes are structurally limited to a tire size of about 28C, so disc brakes are used to provide clearance for mounting gravel tires, which are often used in larger tire lineups.
A dropper seat post is used.
The dropper seat post allows the height of the seat post to be changed with the handlebar lever while riding. This component was developed to cope with such situations, as riding on serious rough terrain inevitably involves parts of the bike that are difficult to ride in a high position.
Originally, dropper seatposts were often used on MTBs, but they are sometimes used on gravel bikes as well.
For example, in Shimano’s GRX and RX810 series, STI levers are compatible with dropper seatposts.
With the current trend toward 12-speed and 13-speed rear shifting, the new trend in MTBs and other bicycles is to use a “front single” without a front shifting mechanism. Gravel bikes are no exception, with an increasing number of gravel bikes equipped with 11-speed or higher components having a single front wheel.
The single-front bike not only avoids situations where the front shift becomes ineffective due to mud or sand, but also simplifies shifting, making it more comfortable on rough terrain where split-second decisions are necessary. Another benefit is that a cleaner front end makes it easier to clean after riding on rough roads.
Wide-ratio sprockets, such as 11-42T, are used for front singles in order to obtain a variety of gear ratios.
What to look for when choosing a gravel bike
Choose a bike with disc brakes!
In order to achieve the world view that gravel bikes seek (to ride comfortably on paved roads and enjoy rough roads as they are), the minimum requirement is to install larger tires. In this sense, it is best to choose a disc road bike that allows for tire clearance.
If the bike is equipped with disc brakes, the frame and fork have enough tire clearance, so you can start with a tire size of about 28C and change to a larger tire depending on where you ride.
It is also possible to install tires as large as 30C on a rim brake-equipped bicycle if it is equipped with long-arch brakes, but this is a rare case, so it is best to choose a bicycle with disc brakes.
If a large percentage of your riding is on rough terrain, a single front wheel is more comfortable.
Gravel bikes are road bikes that can comfortably be used for both “adventure riding” on rough roads and “long rides” on paved roads, but if you do more “adventure riding,” a single front gearshift will improve comfort on rough roads.
Since the gearshift is a single, shifting is simplified, and if the front is set to a compact setting, such as 40T, and the rear maximum is 40T or higher, the road bike can be used on roads where MTBs can be ridden.
It is possible to increase the maximum rear tooth count with a front double, but the total capacity of the rear derailleur may be exceeded, or the rear derailleur for a front double may not have a large maximum tooth count for the low sprocket, so if you want to increase the maximum rear tooth count, a front single is If you want to increase the rear maximum, a single front derailleur is the best choice.