Bicycle frame and its geometry. Bicycle frame Bicycle characteristics and distance between axles

A lot in its behavior depends on geometry - the combination of dimensions and angles of a bicycle. For example, stability, handling, cross-country ability, acceleration dynamics, effective braking, going downhill and uphill, taking sharp turns, and the ability to engage in extreme extreme sports. In ancient times, the geometry of a bicycle was strictly and unambiguously determined by the geometry of the frame. This is not the case at all now. With the advent of front and rear suspensions, the geometry of the bike began to depend on them. Travel, stiffness, damping and shock settings change the geometry and behavior of the bike on the fly! In order not to delve into the wilds, but simply to look around the dense forest with the casual gaze of an expert, let’s consider the main points (see figure below).

A - seat tube, B1 - seat tube, B2 - effective top tube length, C - chainstays, R - fork offset, E - head tube angle, F - seat tube angle, G - base, H - standover, T - front fork extension/extension (Trail), Z - carriage height

1. The angle of the seat tube largely determines the biker’s position and the ease of pedaling: if the tube sticks out vertically and the carriage is located directly under the saddle, it’s uncomfortable to pedal, there’s nowhere to put your hips. The same parameter determines the “weight distribution” of the bike, the distribution of the load on the front and rear wheels. The smaller the angle of inclination from the horizontal, the greater the load on the rear wheel, and the less on the front. On a steep climb, if the biker is sitting in the saddle, the front wheel can become completely unloaded and lose contact with the road. The cyclist risks falling onto his back. But on steep descents everything happens exactly the opposite. The front wheel is loaded, and the further back the biker is moved, the more stable the bike is, and the less likely it is to fall over the handlebars. It is believed that the seat tube angle of 73 degrees (plus or minus 1-2 degrees) provides a correct, comfortable fit and load distribution. This angle is precisely adjusted for the ideal biker with a 32" (813mm) thigh length. For greater comfort and fit of the bike to the cyclist with individual growth, length of arms and legs, etc. You can replace the straight seatpost with a curved one (Thomson). Or simply move the saddle forward or backward. When the saddle is correctly installed, the leg in the lower position is almost completely straightened.

2. The height of the carriage determines the bike's ground clearance - the gap between the road and the pedal when the crank is lowered vertically. Too low ground clearance does not allow you to tilt the bike too much when cornering at high speed; you can catch the pedal or the system stars on a stone, bump, or root while accelerating out of the bend. Therefore, bikes for different riding styles have different carriage heights above the ground; for DH and freeride, the carriage is raised higher, 34-36 cm from the ground. As a specific material, we offer Table No. 1, which was kindly provided by Alexey Madzhuga, where, using the example of KONA bicycles, it is shown how sizes change depending on the purpose of the bike and riding style.

Note. Due to obvious progress in the design and operation of suspension forks and rear shock absorbers and the creation of “stable platforms”, shock absorber travel is last years has increased and, quite possibly, will increase even more. In addition, the higher the carriage is located, the higher the saddle must be raised, the greater the height of the bicycle becomes, the higher the center of gravity of the bike + biker system is located, which affects stability and controllability. It's easier to maintain balance on a tall bike. When a high bike enters a turn, the angle of deviation from the vertical required to compensate by gravity for the centrifugal force arising from movement in a circle (radius) will be LESS than that of a low bike. This follows from the most elementary geometry. It’s easier to ride on narrow forest singletracks on a tall bike, and it’s easier to maneuver it into sharp turns. Let’s repeat: to corner at a given speed and along a given radius, a tall bike must be tilted sideways at a smaller angle than a low one. But when braking and descending, the picture turns out to be the opposite. On steep climbs, descents, and when braking hard with the front brake, a tall bike is more likely to lose its balance, tip over, or tip over the handlebars. To reduce this harmful effect, increase the bicycle base - the distance between the wheel axles. At the same time, they get greater softness and smoothness of the ride, the bike bounces less on potholes, roots and bumps. But a long-wheelbase bike has greater directional stability and fits worse into sharp turns. With a low center of gravity and a long wheelbase, the adhesion of the tires to the road (soil) deteriorates, and during aggressive driving the wheels will slip or skid. When turning, it is useful to have equal grip on both wheels, which means the center of gravity should be in the middle of the wheelbase. To improve handling and maneuverability, you have to “play” with the angle of the steering tube and reduce the rollout of the front wheel (offset, Trail).

3. The head tube angle is measured from the horizontal. Let us note the following: the larger this angle, the closer to the vertical the fork stays are, the faster the bike accelerates, the better the fork handles minor road irregularities. And vice versa, the smaller the angle, the more hollow (sharper) the fork stays are located to the surface, the worse the dynamics and controllability, but the fork swallows large potholes and bumps more easily, and they have less effect on the movement of the bike. If in cross-country the steering angle is usually 71-69 degrees, and the wheelbase length is 100-107 cm, then in DH this ratio will be about 64-65 degrees and 110-117 cm (see Table No. 1). A small angle of inclination of the front fork, combined with a long length of stays, like in bicycle choppers, leads to a deterioration in maneuverability, control efficiency, an increase in the minimum turning radius and the need to turn the steering wheel at a larger angle. The effect of fork rollout and head tube angle on the bike can be seen in the chapter “Stability and Handling”.

4. The geometry of the bike changes when the shock absorbers work. At the moment of braking, when the bike “nods” when the suspension fork is compressed, the base decreases. As a result, the bike becomes more controllable, but less stable. If you load the trunk with a heavy load, or reduce the rear suspension travel (install a shorter shock absorber) on a dual-suspension system, the situation will change to the opposite. The bike will become more stable, but it will be more difficult to control. This is probably familiar to many cyclists. The first trail bikes have already appeared, the geometry of which can be changed on the fly within wide limits. For example, the BIONICON EDISON bike. Replacing the suspension fork and rear shock with longer or shorter ones will affect the stability and handling of the bike. This should definitely be taken into account. These points can be seen in more detail in the chapters: “Stability and Controllability” and “Geometry for Freeride”.

5. Top tube length is defined as the distance from the axis of the head tube to the axis of the seatpost. This length, together with the length of the stem, largely determines the rider's riding position. In addition, it affects the “weight distribution” of the bicycle. A long pipe helps to unload the front wheel, which can cause slippage when cornering. And a short one leads to the fact that the knees touch the steering wheel when pedaling in a “dancer” manner. XC enthusiasts choose a long tube and a long (100-130mm) stem for a low, stretched stance. This makes it difficult to corner and overcome difficult sections, but the main struggle usually occurs on the climbs. For downhill and freeride riding they combine a slightly shortened top tube with a short stem. Therefore, on a slope, the rider moves far back, which ensures proper distribution of the load between the wheels. Additionally, the extra load on the front wheel when the rider is moved slightly forward helps with technical sections.

6. The slope of the top tube determines, first of all, the standover height - the distance from the top tube of the frame to the ground, and the safe distance from the biker’s vital organs to the top tube of the frame. This is very important in extreme sports. In addition, as the height of the frame decreases, its rigidity and strength increases, which plays an important role in jumping disciplines and hard freeride. Recently, lowered top tubes have been used in road and cross bikes. This makes it possible to reduce the number of frame sizes produced and their weight.

7. The length of the chainstays is determined by a line parallel to the ground, running from the axis of the carriage to the axis rear hub. The length of the chainstays affects the weight distribution and dynamics of the bike, and it does not matter whether the biker is sitting in the saddle or standing on the pedals. When the biker gets out of the saddle, the inclination of the seat tube no longer affects the distribution of the load between the wheels. Short chainstays load the rear wheel and increase its traction, and also make the rear triangle more compact, tucked and rigid. The bike climbs hills easier, corners and accelerates faster. Recreational and touring bikes usually have a larger wheelbase and a stretched rear triangle. This worsens the dynamics and requires more energy to climb the mountain. But this has to be done in order to place a large and voluminous bicycle backpack (pants) on the trunk, and not touch it with your heels when rotating the pedals. And a few more words about the differences in bike geometry for different riding styles. The sharper the bike is “tailored” for downhill and hard freeride, the longer the stroke of its shock absorbers, the sharper the angle of the steering tube, the longer the wheelbase and the higher the bottom bracket. The dirt bike has a shortened seat tube, lowered standover and short stem. This is useful for the safety and comfort of the rider when performing jumps and tricks and for greater frame strength.

Yuri Razin. PS. I express my gratitude to Alexey Majuga for valuable advice and recommendations on the geometry features of modern bikes.

On May 20, 2009 the second edition of the book was published Modern Bicycle. The book has been heavily revised and updated. But the cover is unchanged. In St. Petersburg, the book will be available for purchase in the Bukvoed chain of stores, as well as in bicycle shops in the city, and in the regions you can order it through the online store www.tuloma.ru

Continuing the topic of choosing a bicycle, your humble servant began studying bicycle frames. There are many interesting details hidden in this area of ​​​​knowledge that many bicycle owners are not aware of. However, the material I found and translated will undoubtedly be useful for those followers of the cycling movement who want to thoroughly study all the issues related to the design of a bicycle and find out why different bikes behave differently when driving.

When it comes to bikes, geometry is usually talked about like this: “I love the geometry of this bike...”, or “The geometry of our bikes is the best in the industry...”. But what is geometry, and what makes it “good”? Let's find answers to these and other questions about bicycle geometry together!

Geometry is the collection of all the measurements of a bike. Every angle and tube length is part of the overall geometry of the bike. Geometry affects how you feel on a bike like nothing else. This is why you can’t take a cross-country bike (riding on slightly rough terrain) and turn it into a downhill bike (high-speed descent from a mountain). No matter how indestructible you make it, it will still feel out of place and uncomfortable just because its geometry is designed for XC.

Steering angle

Steering angle- this is the angle that the steering tube forms with the surface of the ground. The dumber he is, the faster bike It will turn, and it will be better to drive uphill. A sharper angle makes for slower cornering and makes it harder to drive uphill, but it does improve stability at high speeds. A typical XC bike typically has an angle of around 71 degrees, while a downhill bike has a sharper angle, closer to 65 degrees.

Wheelbase

Wheelbase- this is the distance from the axle to the axle of the bicycle wheels. The larger it is, the more stable the ride. But for increased stability, agility is sacrificed, especially at low speeds. Conversely, a short wheelbase makes the bike more controllable and also allows the bike to spin. Long wheelbases are common on downhill bikes as they greatly contribute to increased stability. A downhill bike can have a wheelbase of 47 inches. Street bikes benefit greatly from the maneuverability of a short wheelbase, which is around 40 inches.

Chainstay

>The length of the chainstay directly affects the width of the wheelbase, which, as I said, affects agility and stability, so a shorter chainstay is made for spirited riding. Shorter chainstays also make the bike easier to handle. In addition, short stays make it easier to control the bike in the air. This is why short chainstays are a must for dirt jumping and street bikes. Short chainstays flex less, transferring energy directly to the rear wheel. A downhill bike's chainstays are around 17 inches long, while street bikes are 14-15 inches long.

Frame height

Frame height, undoubtedly, is the main characteristic of the bicycle. Low-height frames are popular in all mountain biking disciplines simply because no one wants to hit the frame in the worst possible place. Having your foot slip off the pedal can be a very unpleasant experience, especially for men, while a lower frame reduces the likelihood of such an incident. Dirt jumpers and other extreme athletes prefer low frames because they make it easier to perform tricks. A shorter seat tube should, in theory, correspond to a lower frame height, but this is not always the case. Recent improvements in hydroforming (namely bending) aluminum tubing have led to significant reductions in frame height in newer bike models. New lines from Cannondale, Specialized and Santa Cruz - the best ones examples.

Carriage height

Carriage height most important when it comes to making turns. The lower the carriage is, the lower the center of gravity, and the easier the bike will be to turn. However, clearance is also important. If the carriage is too low, the connecting rods, pedals and frame under carriage will hit rocks and various obstacles. The carriage also lowers under the weight of the cyclist while riding. This is also why in touring bikes the carriage is set quite high (14 inches), which prevents the cranks from touching the ground. True, this makes such bicycles extremely unstable when turning and quite useless for anything other than recreational riding. Also, the high landing of the carriage allows you to install 24-inch wheels on some bicycles, instead of 26.

Top tube length

Top tube length- This is the distance between the center of the seat tube and the center of the head tube in a straight line (not taking into account the various bends present on the top tube). Shortening it leads to a reduction in the wheelbase. For each cyclist, the length of the top tube is determined individually; Larger frames have longer top tubes. For some people Long hands and torso, so they are more comfortable on bikes with long top tubes. However, if the geometry of the purchased bicycle seems stretched or, conversely, compressed, there is no need to change it: you can experiment with the length of the handlebar stem or move the saddle.

Seat tube angle

Seat tube angle Similar to head tube angle, only it is shaped by the seat tube and the ground, determining the rider's position on the bike and his offset relative to the cranks. A more obtuse angle moves the rider closer to the cranks, allowing for faster pedaling (by the way, standing pedaling has a similar effect and increased speed).

Thus, the geometry of a bicycle is one of its main characteristics. A seemingly insignificant change in its components at first glance can make the bike more maneuverable, but less stable, suitable for overcoming obstacles or, conversely, for daily walks. Choose a bike with the most suitable geometry for you and ride with pleasure!

Many parameters of the bike’s behavior depend on the geometry of the bicycle (bike) - on the dimensions and angles. It all depends on handling, stability, acceleration dynamics, cross-country ability (in a positive sense), braking efficiency, climbing and descending a mountain, the ability to engage in extreme driving and take sharp turns. Since ancient times, the geometry of a bicycle has been uniquely and rigidly determined by the geometry of the frame.

Today, this is no longer true. Suspensions appeared, rear and front. And, therefore, the geometry and behavior of the bicycle largely depend on the characteristics of the suspension (damping, stiffness, travel) and their settings. In order not to go deeper into the wilds, but just to take a casual glance at this dense forest with the casual gaze of an expert, let’s move on to considering the main points.

WHAT SHOULD BE THE INCLINES AND ANGLES OF THE BIKE, CHOOSE THE CORRECT GEOMETRY OF THE BIKE

For the most part, it sets the cyclist’s position and determines the comfort of pedaling. If the tube is located vertically and the carriage is located directly under the saddle, then pedaling is inconvenient, there is nowhere to put the hips. Another parameter determined by the inclination of the seat tube is the weight distribution of the bike, in simpler terms, the distribution of the load between the rear and front wheels. The smaller the angle of inclination (it is measured from the horizon line) and the higher the cyclist’s position, the less load falls on the front wheel and the greater the load on the rear wheel.

On a steep uphill climb, while the cyclist is sitting in the saddle, the load on the front wheel of the bike can disappear completely and there will be a loss of contact with the road. And the cyclist, at this time, risks falling on his back. On steep descents, the process occurs in reverse. The front wheel is loaded, and the more the cyclist is shifted back, the more stable the bike is, and thus reduces the likelihood of falling over the handlebars.

It is generally accepted that if the angle at which the seat tube is tilted is 73° (with an error of 1°...2°), the cyclist is provided with a correct, comfortable fit and his weight is correctly distributed. This statement is valid for an ideal cyclist whose thigh length is 813mm (32 inches). To make an additional adjustment to this angle and adjust the bike to the actual dimensions of the cyclist (length of legs and arms, height...), you can replace the straight seatpost with a curved one (Thomson). Or you can move the saddle back or forward, which is even easier. If the saddle is installed correctly, in the lowest position of the pedal the leg should be almost completely straightened.

WHAT SHOULD BE THE HEIGHT OF THE GREAT CARRIAGE?

This parameter determines the bike's clearance - the distance between the road and the pedal at the moment when it is in its lowest position. If the ground clearance is too low, this will not allow you to tilt the bike much, then during high-speed cornering there is a high probability that you will catch the pedal on a root, bump, or stone while accelerating when exiting the bend.

For this reason, bicycles designed for different ways skating, the height of the carriage above the ground varies. For example, for freeride and DH the carriage is raised much higher than in road bikes (approximately 34...36 cm). As a clear example, Table No. 1 is given (which was kindly provided for this article by Majuga Alexey), which, using the example of KONA bikes, demonstrates the change in geometric dimensions depending on the riding style and purpose of the bike.

Note: Due to the fact that there has been clear progress in the design and operation of rear shock absorbers, suspension forks, as well as the creation of stable platforms, shock absorber travel has increased significantly in recent years and there is a high probability that, over time, it will increase even more.
In addition, if the carriage is located high, the saddle also needs to be raised higher; accordingly, the height of the bicycle increases and the center of gravity of the mobile “bicycle + cyclist” system rises. There is no doubt that this affects handling and stability. On a tall bicycle it is easier to maintain balance, and when making a turn, the angle of inclination, which is designed to compensate with the help of gravity, occurs when circular motion(radius) centrifugal force will be smaller than that of a bicycle with a low bottom bracket.

This follows from a school geometry course. Accordingly, a high-riding bike makes it much easier to ride on forest singletracks and easier to navigate sharp turns. This means, once again, to negotiate a bend at a given speed and along a fixed radius, a low bike needs to be tilted sideways by more than a high angle. However, when descending and braking, everything looks completely opposite. During steep ascents, descents and when braking instantly using the front brake, on a high-riding bicycle, the likelihood of losing balance, falling backwards or somersaulting over the handlebars is much greater. To minimize this unpleasant effect, they try to increase the wheelbase of the bike - the length from the axis of the front wheel to the axis of the rear.

At the same time, greater smoothness and softness of the ride is achieved, the bike bounces less on bumps, potholes and roots. But a bicycle with a large wheelbase has greater directional stability and takes sharp turns worse, which, again, can be understood thanks to a school geometry course. To improve maneuverability and controllability, you have to “twist” the angle of the steering tube and make the Trail (front wheel offset) smaller.

HOW WILL THE BIKE GEOMETRY CHANGE WHEN REPLACING THE FORK

It is worth noting the following point. The greater the value of this angle, the closer to the vertical plane the fork stays are, the higher the acceleration speed of the bicycle, and the better the fork handles all kinds of small irregularities and bumps on the road. And, accordingly, if the angle decreases, the fork stays will become flatter relative to the surface (sharper), as a result, controllability and dynamics deteriorate, but at the same time, the fork begins to tolerate large bumps and potholes more easily, and they, in to a lesser extent, affect the movement of the bicycle.

For cross-country bikes, the steering angle is most often from 71 to 69 degrees, and the distance between the wheel axles is from 100 to 107 cm, and in DH the angle is approximately 64...65 degrees, and the wheelbase length is 110...117 cm (See. Table No. 1). The low inclination of the front fork paired with long stays, which is quite often used in bicycle choppers, leads to a significant deterioration in the maneuverability of the bicycle, the sharpness (efficiency) of control, an increase in the minimum possible radius of turn and forces the steering wheel to be turned to a higher angle.

TRAIL (FRONT WHEEL REMOVEMENT) AND BICYCLE FRONT FORK PARAMETERS

A little experiment. If you place a bicycle of the correct configuration vertically on two wheels, take it by the frame and tilt it to the side, then the steering wheel itself should turn in the same direction. The reason for this phenomenon lies in the geometry of the steering column and front fork. It is these details that determine the location of a pair of important points between each other. Points A are the points of contact between the road and the front wheel, and points B are the points of intersection of the axis passing through the steering column and the road. The relative position of these points determines not only the direction of rotation of the steering wheel when the bicycle is tilted, but also its controllability, directional stability, stability during turns, control rigor and much more. Bikes can be divided into two types: AB and BA. An AB-type bicycle is one in which the point of contact of the front wheel and the road is located in front of point B (Figure No. 2a). A BA-type bicycle is one in which point A is behind point B (Figure No. 2b).

If you tilt an AB-type bicycle in one direction, the handlebars will turn in the opposite direction and, for a very clear reason, point A, at which the friction force is applied, will be closer than the axis of the head tube (point B). A bicycle, if turned without hands, will fold in half like a book and fall to the ground with a thud. The front wheel and handlebars of a BA-type bicycle react completely differently to the tilt of the bike - they will tilt towards the tilt of the bike themselves and without the help of their hands.

And with balanced angles and dimensions, the bike will return to an upright position exactly as if the handlebars were turned by hand; the handlebars just need a little help, adjusted in the right direction, and everything will turn out just fine! For this reason, AB-type bikes cannot be found in stores.

NOW A LITTLE ABOUT THE GEOMETRY OF THE FRONT FORK.

The designs that are shown in Figure 3, a) and b), will give us an excessively large distance from point A to point B, which causes the effect of over-stability of the bike. The longer the distance from one of these points to the other, the higher the moment of force that turns the front wheel and, naturally, the steering wheel in the same direction in which the bicycle is tilted. The result is clear, vertical and directional stability are quite good, but handling is worse than ever. For this reason, in order to reduce the distance between these points, the fork on bikes is bent forward, Figure No. 3, c).

However, even if the bicycle is equipped with a straight fork, its inclination changes relative to the axis passing through the steering column, or the cocks to which the front wheel is mounted are moved forward. Figure No. 4. The distance from the axis passing through the front wheel hub to the axis of the steering column has different names, Fork Offset, and Rake, and here sometimes you can come across run-out, offset or offset of the fork. The value of the fork offset R, most often, falls within the range of 30 to 50 millimeters.

If the fork offset, the angle of the axle passing through the steering column, and the actual diameter (taking into account the thickness and deformation of the tire) of the wheel are known, then you can easily calculate the distance between points B and A. This distance is called Trail or rollout (coast). front wheel, it happens that it can be found in catalogs. As a result, with a known Trail, you can calculate the controllability (stability) coefficient (Ku), which is equal to: Trail (T), divided by the sum of the same Trail and the length of the bicycle wheelbase (G), the result of the operations performed multiplied by 100%. Let's look at the formula: Ku=(T/)*100%(1), there is nothing complicated. U modern models bicycles Ku is within 5 ... 7.5%, and usually the value closest to the stability limit is selected. The reason for this is quite simple - a bicycle of this design is easier to control.

HOW DOES THE GEOMETRY OF A BICYCLE CHANGE DURING THE OPERATION OF SHOCK ABSORBERS

At the moment when braking occurs and the bike nods while the suspension fork is compressed, the wheelbase decreases, but at the same time, the Trail decreases even more, and therefore the Ku becomes smaller. It turns out that during braking, the bikes' controllability becomes greater, but stability decreases. The same situation is observed when pedaling while standing, at the moment when the cyclist brings his body closer to the steering wheel and during descent from a hill, especially if intensive braking is carried out with the front wheel.

Now, if you load the trunk with a heavy load ( beautiful girl) or make less travel of the rear shock absorber (install a shorter shock absorber) on a dual-suspension system, then the position will change to the exact opposite. The trail will become larger, the Q will increase, the bike will be more stable, but it will become more difficult to control. This is no doubt familiar to most bike tourists. With a tightly loaded trunk, the bike rides confidently, like a tank, especially if the acceleration is good. But making a turn or driving along a winding path at low speed is, oh, so difficult.

Today, many bikes designed for extreme sports are equipped with long rear stay dropouts, making it possible to move the rear axle within a wide range or install a wheel with a smaller diameter instead of 26 - 24 inches. No one will be surprised by the fact that during this the handling and stability of the bicycle changes.

The first trail bikes are already on sale, the geometry of which changes directly while riding, and within a wide range. For example, the new product of the season, the BIONICON EDISON bicycle. Using an industrial valve used in pneumatic lines and pneumatic automation devices, you can change the frame geometry by 6 degrees! The head tube angle is from 67.5° to 73.5°. Seat tube inclination from 71° to 77°. Move front shock absorber from 69 to 147 mm, rear shock absorber travel 142 mm, taking into account the wheelbase of 1056 mm. Now, on one bike you can effectively ride steep slope, and roll in cross-country style.

Tuning a bike or how to improve the ride quality of a bike Replacing the rear shock absorber and front suspension fork with shorter or longer ones affects the handling and stability of the bike. This must be taken into account.

Top tube length is the distance from the seatpost centerline to the head tube centerline. This distance, together with the length of the stem, for the most part determines the rider’s position. In addition, the size of the top tube significantly affects the weight distribution of the bike. A long pipe allows you to unload the front wheel, which can cause slippage during turns. A shorter top tube can cause your knees to catch on the handlebars when pedaling like a dancer. People who prefer to ride XC style usually choose a longer tube with a long stem (100 to 130mm) to achieve a low, stretched riding position.

This makes it difficult to take sharp turns and overcome difficult sections, however, the main struggle, most often, occurs during climbs. For freeride and downhill riding, a combination of a slightly shorter top tube and a short stem is used. Thanks to this, on a slope the cyclist transfers his weight far back, thereby ensuring correct distribution of the load on each wheel. In addition, the additional loading of the front wheel, when the cyclist moves slightly forward, will help overcome technically difficult areas.

BIKE TOP TUBE TILT ANGLE

First of all, it determines the height of the standover - the distance from the top tube of the bicycle frame to the vital organs of the cyclist. This parameter is very important for extreme species sports

In addition, the construction height of the bicycle frame becomes smaller, as a result of which its strength and rigidity are even greater, which is important for jumping disciplines and hard freeride. Recently it has become fashionable to use a lowered top tube in motocross and road bikes. This makes it possible to reduce the size of the frames produced and their weight.

LENGTH OF BIKE STAYS

The length of the chainstays is determined along a line parallel to the horizon, from the axis of the rear hub to the axis of the carriage, the length of which affects the dynamics of the bicycle and its weight distribution. Moreover, it doesn’t matter whether the cyclist is in a sitting or standing position, this is the difference between the influence of the length of the chainstays on weight distribution and the influence exerted by the inclination of the seat tube. Because when the cyclist gets out of the saddle, the angle of the seat tube no longer affects the distribution of weight between the wheels.

Short stays increase the load on the rear wheel and help increase its grip on the road, and, at the same time, make the rear triangle more compact, rigid and tucked. The bike rides uphill easier, corners faster and accelerates faster. For touring and recreational bikes, the base is most often increased and the rear triangle is stretched. This makes the dynamics worse and forces you to apply more energy to climb the mountain. But these sacrifices have to be made in order to place a voluminous and heavy bicycle backpack on the trunk and not cling to it with your heels while pedaling.

And a few more words about the differences in the geometry of bicycles in accordance with different styles skating.
The more a bike is designed for downhill and hard freeride, the longer the shock absorbers will travel, the sharper the head tube angle, the higher the bottom bracket position and the longer the wheelbase. The dirt bike is distinguished by a shortened seat tube, low standover (the distance from the center of the seat tube to the ground) and a short stem. This ensures the safety and comfort of the cyclist during tricks and jumps, and higher strength of the bicycle frame.

The article is not bad, although it has its pitfalls, which were kept silent about. But in such a short note it is impossible to touch on all the points that determine the loading format, since it is determined by the type of coverage on the trip and the selection of equipment, the level of the group, the idea and goals of the trip... etc. etc.. They already reminded us about the trailers. Everyone loads as it is more convenient for them! This is so that it won’t be considered that I’m criticizing that much, further on in the message. So I’m just pointing out the unmentioned features of the mentioned format
Ease of movement is a good thing, but usually the restrictions that it imposes on changing weather conditions, travel conditions, and the choice of overnight stay remain behind the scenes.
It’s trite, everything seems to be fine with the load offered, but few people think about the volume of water that it allows to bring for an overnight stay, so this initially forces one to spend the night either near the water or closer to housing.

Stanislav Ustinov wrote:

I assume that a person sits on the rear wheel 60-70% of their weight, and therefore do not put all the load in the rear bag. When the weight is distributed throughout the bike, maneuverability and stability in turns, climbs and descents are improved. And the ride of a bicycle with a distributed load is easier than that of a bicycle with an overloaded rear wheel.

February 25, 2016

Bicycle frame(bicycle frame)- This is a fundamental component of any bicycle. These depend on her important features, like: the further purpose of the “bike”, riding style, convenience, comfort and of course safety. The strength of a bicycle also directly depends on the bicycle frame. Today there are a lot various options bicycle frames, they differ in material, geometry and other important details. To understand all this, it’s enough just to look at a certain average version of the frame and understand what parts it consists of and what the individual components are correctly called.

Bike frame components

Any “classic” bicycle frame is structurally composed of tubes, which can be made of various materials, combinations of materials, alloys or composites. To obtain the required (balanced) ratio of strength/flexibility characteristics in each specific case, combined materials are often used. Pipes may be free form and sections, with square or round profile.

The frame design that is familiar to everyone is two triangles, front and rear (these triangles can be imagined virtually if you also mentally examine the frame from the side).
They can have any shape, not necessarily a perfectly even geometric shape, but they still retain this name. The final look depends on the imagination and intentions of the manufacturer or the “designer” of the frame, if he was involved during its creation. Although anterior triangle can be considered as such very conditionally (since it consists of 4 pipes, and not 3), the following elements can be distinguished in its structure: headset, head tube, top tube and seat tube.

Posterior triangle comprises: seat tube, seat stays and chain stays. At the bottom of the frame, where the main tube meets the rear triangle and meets the seat tube, there is a

The lower rear stays go into mounting brackets rear wheel, or they are also called dropouts. The hind feathers also include brake system mounts v-brake, but nowadays almost all of them are mounted on disc brakes.

The frame design sometimes differs from the “classic” one due to various tricks from the manufacturers and the intended purpose of the bicycle. But even in this case, the basic principle and names of the frame elements are retained, even if their shape undergoes changes.

To ensure the immediate functionality of the future “bike” and all its systems, the bicycle frame includes in its design individual elements that serve to install specific components. Let's take a closer look at these frame elements:

IN steering glass is installed steering column (headset), V hole for carriage- installed accordingly bottom bracket, and in seat tube hole is installed seatpost together with saddle.

Rear wheel hub mounting brackets or "dropouts" can be vertical, horizontal or adjustable.
Vertical dropouts the most convenient and easy to use - they allow you to quickly put the wheel in place, and do it as smoothly as possible (chain tension in this case is provided by the rear gear selector, separate manual adjustment is not required).

Horizontal dropouts Nowadays they are used less and less due to the specificity of the design. With their help, the chain is tensioned, which is especially important for “singlespeed” (bicycles with one gear, without a rear derailleur). Another use case could be in tandem with a planetary hub. However, with enough force, the wheel axle can move. To prevent this, there are special axle clamps.

Adjustable dropouts come in a wide variety of variations: with or without holes for mounting the rear derailleur. They allow, as the name suggests, the “base” of the bicycle to be flexibly adjusted within small limits. These dropouts are easy to change and the bike can easily be converted to a single speed.

Modern bicycle frames also often include additional structural elements for attaching accessories and other add-ons. devices. On most frames you can see holes for installing a bottle cage, and fasteners for brake cables and gearshift systems.
The latter are often replaced by holes on the frames high class, to pass the cable jackets inside, thereby improving the aesthetic appearance of the bicycle, increasing comfort and reducing the unpleasant effect of chafing on the jacket or frame. Some frames come with additional accessories holes for fixing wings, which is usually typical for road and touring bikes.

Let's take a closer look at some frame elements and try to understand how compatible components are selected for each specific frame and what differences there are:

Steering glasses (headset) on the frame they can be regular or integrated. Taking these features into account, the steering column is selected for the glass.

Conventional steering glasses They are much more common, they are more often found on sale and do not involve any complex features. The easiest way to find and select a steering column for such steering glasses is to do this taking into account your own riding style preferences.

Integrated steering columns are considered a more professional and thoughtful engineering solution, easy to install and require virtually no maintenance, but can damage the frame in some cases (or lead to expensive repairs).

You can read more about steering columns and compatible steering columns in.

Carriage unit frame consists of glasses, in which it is installed carriage. This glass varies in length and type of thread, depending on the features of the frame.

There are three types of frame threads:

1. English thread (BSW, 1.37 in x 24 TPI);
2. Italian thread (BSC, ITA 36 mm x 24 TPI);
3. French/Swiss thread (M35×1);

There are also glasses with integrated systems. In them, bearings with cups are pressed directly into the frame, and the axle remains the central element. Such systems are called "Pressfit" and they are gaining popularity in the design of professional frames recently. There are also eccentric carriages that rotate in their seat and feature automatic chain tensioning functionality. The latter are used extremely rarely; they are an alternative to a drive with a front gear shift system.

Seat tube frame is equipped seat clamp. It can be integrated (only on older frame models) or external.
Depending on the diameter of the seat tube, clamps come in the following most common standards: 27.2 mm; 30 mm; 31.8 mm; 34.9 mm;

External seatpost clamps can be:

• Eccentric- clamped without tools by hand or with an application physical strength. Convenient, understandable and easy to use for everyone, do not require additional tools.
• Bolted- fix the seatpost with a bolt, usually a hexagon. Less convenient, they require a tool to adjust the tightening force, but they are more reliable.

The frame design can also vary significantly in the presence or absence of rear suspension and its varieties.
As a rule, in such cases, the bicycle frame will have a detachable rear triangle and some kind of structure (individual) on which the shock absorber itself will be attached.

Frame geometry

A bicycle frame and its intended purpose largely depend on geometry, the most significant and significant parameter for this product. The geometry of the frame is determined by the length of the pipes and the angles at which they are connected. The most significant and determining parameters of the frame geometry can be noted: the angle of the head tube, the angle of the seat tube, the length of the top tube and the length of the seat tube.

Analyzing the frame geometry in detail, it is worth highlighting some characteristic frame dimensions, which are often indicated by one or another manufacturer. These dimensions are quite significant when choosing, especially taking into account the intended riding discipline:

• Saddle height- distance from the center of the carriage to the middle of the saddle
• Stack- vertical distance from the center of the carriage to the top point of the steering column
• Reach- horizontal distance from the center of the carriage to the top point of the steering column
• Bottom braket drop (carriage indentation)- the distance that determines how low the center of the carriage is relative to the center of the rear bushing
• Handlebar drop- distance that expresses the vertical difference between top part saddle and handlebar top
• Saddle seatback- horizontal distance between the front of the saddle and the center of the carriage
• Standover height (full height)- height from the ground to the top tube of the front triangle
• Front center- distance from the center of the carriage to the center of the front bushing
• Toe overlap- determines the distance from the rider’s foot on the pedal to the front wheel while turning the latter

The geometry of the frame plays a decisive and most important role in the behavior of the bicycle on the road, its stability, and the responsiveness of the steering wheel. It also determines the convenience and comfort of landing, affects the acceleration and braking characteristics, and the overall dynamics of the bicycle. You should pay close attention to these dimensions when choosing a frame to suit your individual needs and wishes. There are a number of the most important practical dimensions that should be taken into account first:

• Top tube length. Measured from the center of the steering column to the center of the seatpost in a straight horizontal line. This parameter directly affects the stability and maneuverability of the bike. The higher the length, the more stable and responsive the bike will be.
• Steering column angle. The angle between the steering tube and a straight vertical parallel line. A larger angle determines better maneuverability of the bike.
• Seat tube angle. Determined by the inclination of the seat tube in relation to a straight parallel vertical line. This characteristic is responsible for the shift in the center of gravity, namely, it answers the question: “Does the center of gravity shift and how much when the cyclist sits in the saddle?” The bike’s predisposition to extreme elements and tricks depends on this, and also determines confident grip on the surface (if the angle is larger) or a greater predisposition for dynamic riding during high-speed pedaling (if the angle is smaller).
• Wheelbase. The distance between the centers of the front and rear wheel hubs in a straight horizontal line. The longer the wheelbase, the more stable, maneuverable and stable the bike will be.
• Length of the rear triangle chainstays. Measured from the center of the bottom bracket to the center of the rear wheel hub. The shorter the length, the more reliable and durable the frame and the better the bike’s grip on the surface, and the more responsive the bike is when steering and other high-speed maneuvers.
• Ground clearance/height to carriage assembly. The distance between the lowest point of the bicycle (bottom bracket) and the ground. Affects maneuverability and speed. The higher the height, the more confident and stable the bike is off-road, and the less likely it is to catch the frame on any unevenness or obstacles. But along with this happens big loss speed and dynamics.
• Stem length. Measured from the center of the steering column to the handlebars (stem). Significantly affects maneuverability and ease of landing.

Overall frame size is traditionally measured along the seat tube, from the center of the bottom bracket, to the center of the top tube (where it intersects/meets the seatpost). So the “size” of the frame is determined and the bike in general. However, there are other measurement methods.

The size of the frame is directly related to the height of the person who
intends to ride a bicycle assembled on the basis of this frame. This relationship can be roughly represented as follows: The XS size frame is designed for a height of 152-162 cm; frame size S for height 162-172 cm; frame size M for height 172-182 cm; frame size L for height 182-192 cm; frame size XL for height 192 and above;

It is customary to select a slightly smaller frame size for extreme riding disciplines in order to increase controllability and maneuverability for performing tricks and various jumping elements.

Frame materials

A bicycle frame can be made from various materials. Since the dawn of cycling, this has traditionally been steel, but frames can also be made of aluminum alloy, carbon fiber, titanium, thermoplastic, or even bamboo and wood. Each material provides a combination of its own unique characteristics and inherent disadvantages. Also recently, combinations of different materials (composites) are often used to achieve the necessary balance of low weight and high structural strength. When choosing a frame material, the following properties play an important role:

• Density- the final weight of the frame depends on this parameter
• Rigidity- has little effect on the transmission of pedaling energy and rider comfort. Determines the ability of the frame to deform without destruction.
• Tensile strength or transverse strength- determine the force with which the material is deformed.
• Tension/elasticity- determines how much the material must be deformed before it breaks.
• Fatigue- determines the durability of the frame in the future of active use.

Brief advantages and disadvantages of the most common frame materials, making it easier to choose a frame for individual needs and riding style:

• Steel frames. For the production of frames, chrome-molybdenum steel is currently most often used, which is distinguished by its excellent strength, reliability and endurance, as well as the invariably good elasticity of the material (the frame feels comfortable in motion as it “plays” a little, although thereby losing in the dynamics of movement) .
  Frames made from this steel are fairly easy to repair if they break and are very durable due to their excellent fatigue characteristics. But the disadvantages of such frames are also very significant, including high weight compared to frames made of other materials (several kilograms for the same size) and susceptibility to corrosion. To combat corrosion, the frame is coated with a special compound, but if the paint and varnish coating is damaged, it can be very difficult to stop the development of corrosion. Consequently, such a frame is not so unpretentious and durability is negated by such problems. Of course, corrosion is not as severe as compared to a car body, for example, but a bicycle is quite capable of losing its presentation and reducing its strength over time. A bicycle frame made of steel is often chosen by lovers of tourism and quiet rides for a fairly balanced combination of characteristics, good comfort (which is important on long trips) and reasonable cost.
• Titanium frames. The use of titanium in bicycle production is borrowed from aviation. But, despite the fact that titanium has a number of undeniable positive qualities such as: increased specific strength and incredible low weight(often lower than aluminum analogues with greater strength), corrosion resistance, increased elasticity (titanium frames are considered one of the most comfortable) and excellent fatigue characteristics (and therefore durability), such frames have a number of significant disadvantages.
  The complex technological process of manufacturing such a frame and the high cost are not always justified, as well as almost complete non-repairability in case of damage. Titanium frames most often become the choice of understanding professionals who have been involved in cycling for a long time and are willing to put up with the inflated price of this fundamental component.
• Aluminum frames. More precisely, frames made of various aluminum alloys with impurities, since aluminum in its pure form is a fairly soft metal. Aluminum alloys are divided into series, so in the 7000 series an admixture of zinc is used, and in the 6000 series magnesium is added. Aluminum frames are the most common today and are in demand due to the ideal compromise in price, quality and set of characteristics.
  These frames are practically not subject to corrosion, are characterized by low weight, but at the same time reduced elasticity and increased rigidity. In practice, they are less comfortable and not really designed for bicycles that are expected to travel long distances. It is believed that bicycles based on such frames are more maneuverable and responsive, with better acceleration dynamics. Aluminum frames the best way suitable for extreme disciplines. Among the disadvantages of this material, it is also worth noting its unsatisfactory fatigue characteristics. Recently, manufacturers are increasingly declaring a lifetime warranty on their aluminum frames. In the manufacture of aluminum frames, an interesting, innovative technology hydroforming, which eliminates the presence of seams in the frame structure or reduces their number, making the final product more aesthetically attractive.
• Carbon frames (carbon fiber). This frame is made of carbon fibers impregnated with special adhesive resins. This material is a classic composite. It has sufficient strength for a typical bicycle frame, but is burdened with a bunch of disadvantages, such as: an unusually complex manufacturing process and at the same time the highest cost of the frame (often unjustified), low impact strength of the material, and absolute non-repairability.
  Such a frame is enough for a couple of years of active use, and the cost is many times higher than any analogues. Such frames are suitable for professional cyclist racers who chase every gram excess weight so as not to lose performance. It is advisable to use such bicycles for racing competitions, keeping them in “preservation” in a warm room for the remaining time. The only worthy significant advantage of a carbon frame will be the lowest weight of the frame among other analogues, and also the fact that this material is simply not susceptible to corrosion.
• Other rare materials practically never found in mass production.
  Among them, aluminum alloys with rare impurities and various types of wood (including bamboo) can be distinguished.

In the manufacture of bicycle frames and individual pipes, manufacturers sometimes use "batting". This technology makes it possible to slightly reduce the final weight of the frame by using different wall thicknesses of the frame tube and at the same time varying the density of the material in different most loaded areas of the frame. Typically, such a frame is denser at the joints, which is determined by the necessary margin of safety at these points, taking into account the increased load on the unit. Batting can be double or triple.