29er wheels on gravel bike

This year I have been cycling more often, and I will gradually follow up on some forums and websites, activities and equipment.


Last year, it was discovered that the mountain has kept up with the pace of the road, and the two major manufacturers have begun to produce the rear 10-speed mountain transmission system. Now it has been found that 29-inch (29er) mountain wheels are popular in XC competitions. Of course, Giant Trance is also in China. The 29er version was released.


Come and learn about the secrets of the 29er wheels (transferred from: Love Off-Road, translated from Steve Worland's article on Bikeradar.com)



      29er: A new lineage of mountain bikes, which is different from the 26-inch wheel diameter of traditional bicycles. It adopts a 29-inch design and brings many exciting new features! Some people may think that these "big wheels" are like a car that a clown rides, but in fact, most of them have not studied in depth to get this idea.



      

     Although resisted by a small number of people, the 29er is gradually becoming the mainstream of mountain bikes. Every year, more and more 29er can be seen in car shops and mountain roads. In 2010, the mainstream brand 29er in American and British car shops was almost out of stock! And many world-class drivers are using these "big wheels" to win one race after another. It's time to get our attention.


      Size determinism 29er 26er

    

    Let's go back to 1986, Dr. Alex Moulton, who is known for inventing the comfortable bicycle with small wheels. His car is an all-terrain bike with 20-inch wheels. Unfortunately, Moulton ATB (All-Terrain Bike) has an essential flaw. Those small potholes that can be completely ignored when you ride the current 26-inch car are all reflected in his car. Although in the era when most mountain bikes were all-hard frame structures, his suspension ATB had amazing comfort and handling, this 20-inch car was inevitably eliminated by the times.

    

     If you have ever rode a BMX on a standard mountain trail, you will never forget the painful experience. The small wheel diameter and small wheelbase are not conducive to riding on rough terrain. Imagine that when other conditions remain the same, the arc of the big wheel touching the ground can make it easier to pass uneven ground. But can we assume that big wheels can pass these terrains faster? This is not always the case, because there will be more complex situations that need to be considered.




     Take the shock absorber. In theory, all forms of suspension, including the 29er, seem to make the terrain flatter. But installing shock absorbers on a 29-inch mountain bike is much more complicated than on a 26-inch bike. Because the wheels have become larger and the space for shock absorbers has become smaller, the frame must be redesigned. And the larger wheels need to redesign the frame geometry to make the car work in its best condition.


      Larger wheels and tires also make the car heavier, which is not conducive to speed. Although 29-inch wheels are easier to bulge through the diamond shape, the performance on other types of potholes is not exactly the same. Small wheels have low momentum and are easy to accelerate, but large wheels can better maintain rotational inertia. Therefore, even before we find the best frame geometry design, we should not arbitrarily say that they are better because the big wheels roll more smoothly.


     Take the shock absorber. In theory, all forms of suspension, including the 29er, seem to make the terrain flatter. But installing shock absorbers on a 29-inch mountain bike is much more complicated than on a 26-inch bike. Because the wheels have become larger and the space for shock absorbers has become smaller, the frame must be redesigned. And the larger wheels need to redesign the frame geometry to make the car work in its best condition.


       Larger wheels and tires also make the car heavier, which is not conducive to speed. Although 29-inch wheels are easier to bulge through the diamond shape, the performance on other types of potholes is not exactly the same. Small wheels have low momentum and are easy to accelerate, but large wheels can better maintain rotational inertia. Therefore, even before we find the best frame geometry design, we should not arbitrarily say that they are better because the big wheels roll more smoothly.


     What size wheel should you use?


       The current mountain bike market is still dominated by 26-inch wheels, which is easy to understand. Because for average-sized riders, a thick tire can already meet the requirements of mountain riding. Moreover, the 26-inch wheels are effortlessly installed on the frame of ordinary structure size without considering the problem of insufficient clearance after being stained with mud.

      

     Popular science time. The dimension of mountain wheels refers to the diameter from the edge of the tire (tire). However, due to the difference in tire thickness and tyre tooth height, 26 inches is only a rough figure. Very thick tires can sometimes make the wheel diameter reach 27.5 inches, or even too large to fit ordinary front forks and chainstays.



    In fact, the 26-inch wheels with thick tires can give you the similar feeling of 650B (27.5-inch) wheels with ordinary tires. The 650B specification is between 26 inches and 29 inches. Some people think that this is a better compromise solution, which not only provides the sensitivity we are familiar with, but also improves the passability.


      The 650B wheels can be made lighter and stronger than the 29er, and their frame looks neater and slenderer than the 29er, and the gap between the wheels and the frame is larger. There is no doubt that 29er and 27.5er, if there are more rims and tires to choose from, are a good choice for you who want a smoother feel, especially when you don't need a suspension fork. For those tall riders, it is a very good new choice.

    

     In the foreseeable future, 26-inch small wheels will still occupy the market of ordinary drivers. But there is no doubt that 29er is quietly carrying out a revolution. Now, let's take a closer look at why 29er has become more and more popular.

    

     29er's fledgling days

    

     When the first mainstream 29er went on the market, they had already shown great potential, but they were still limited by the limited choice of front forks and the painstaking imitation of the 26-inch frame geometry.

    

      Gary Fisher’s early research is very useful, but in recent years, designers have really begun to realize the difference in the ideal geometric design of the 26-inch and 29-inch frames. It's much more than just adjusting the angle of the frame. The length dimensions of the front fork, stem, top tube and bottom bracket all have a great influence on the overall stability and riding feeling.

    

     Later, we must also start to consider the pros and cons of the longer rear fork and wheelbase, as well as the impact of the change in tire contact area on the grip. Just like the 26-inch car, research in these areas of the 29er is still ongoing.



      Drivers switched to 29er because they love its faster speed and better passability. For professional players, on the same track, these advantages of the 29er don't seem to improve their overall time. But as their experience grows, they seem to become more confident in the face of rough terrain.


     Remember, improvement in comfort and self-confidence usually equates to faster speed. This explains well why some of the small children players in the World Cup XC competition can ride 29er to achieve great success. When they feel that riding is easier, they save time. Below, let's take a look at some of the debates about 26er and 29er.

    

     How are the wheels measured?

    

     26 inches and 29 inches refer to the diameter of the tire (roughly because the tires are not the same). Coarse tires mounted on 26-inch wheels may actually reach 27 inches or more. Thick tires can roll more smoothly than thin tires (referring to height), so large wheels can provide better comfort and traction.

    

     A compromise choice, but also very difficult to find on the market, the 650B wheels have an outer diameter of 27.5 inches and can be mounted on some 26-inch front forks and frames. Some front fork manufacturers are now beginning to change the arch bridge height of their products to accommodate 26-inch thick tires and 650B wheels.

    

    Why is scrolling smoother?

    

    The main reason for the smooth rolling of the big wheels is related to the arc angle. Try rolling a hula hoop and a glass to compare. There are some other differences, but you already probably understand why.

    

     A larger and gentler arc can form a gentle connection between the sharp corner and the ground. That's why riding the BMX down the stairs is much more difficult than riding a mountain bike. To explain logically, if the wheel is made big enough, when it presses over an angular protrusion, it is like pressing on a slope.



      What about 29er wheel grip?

    

     There is a common misconception about 29er and 26er grip: if a rider sits on 26er and 29er with the same tire pressure, their ground contact area is theoretically the same. But in fact, even if you use the same brand and the same series of tires, due to changes in volume and shape, you will get a wider footprint on the 29er.



    29er frame geometry?

    

     There are many factors to consider here. A typical 29er will feel more stable than a 26er. Part of the reason is because of the longer wheelbase and the longer rear end designed to provide room for large wheels. Although these can be imitated on 26er, they are rarely done in practice.

    

     Another reason for increased stability is that although the 29er’s axle height is 1.5 inches higher than that of the 26er, the center of gravity of people actually decreases when you get in the car. Even if the center of gravity of the 29er's wheels is higher than that of the 26er, the overall center of gravity is lowered when the driver is included.

    

    In order to get a better geometric angle, designers also began to change the size parameters of the front fork to increase the handling performance of the 29er. With the introduction of more 29er forks by various brands, the disadvantage of 29er on the technical track will become history.



     Why don't all players use 29er?

    

    In 2009 and 2010, the championship of the American men's/women's marathon XC race was won by 29er drivers. Some Trek team drivers have also made significant progress after switching to the 29er. Todd Wells won two U.S. national titles after riding his new 2011 Lightning Epic full suspension 29er. Riders such as Willow Koerber and Heather Irmiger also proved that small riders can also adapt well to large-wheel mountain bikes.

    

     coincidence? It may be, but look at the actual results. It seems that XC players' unfriendly reservations about mountain bike design are changing, even if it may only be to satisfy the sponsor's wishes.

    

    Who is 29er best for?

    

    Many companies are testing 29er DH models and more and more XC players use 29er. Is this just because of market pressure or because 29er is genetically more suitable for some riders than 26er? In this article, we have discussed many controversial technical issues and concluded that different drivers are suitable for different options.

    

    Riders who enjoy the smooth rolling feel of the 29er may be able to ride faster. But for those drivers who can't tolerate the delay caused by the 29er's immediate acceleration, it feels even worse. To put it simply, 29er actually affects your subjective feeling of riding, rather than having an obvious objective speed advantage.