How to choose a bike system

Bicycle mounting method

  • Integrated Bottom Brackets. These are the bottom bracket shafts connected together with the bicycle crank. Due to this, strength increases, weight and cost are reduced;
  • Not integrated. they have a separate component, with the help of which a crank of a certain type is attached;
  • Cartridge and non-cartridge. In the first case, the bearings are pressed into the cartridge at the factory. For the second case, the principle is similar, but if the cartridge is not cartridge, dirt and dust may get in.

Varieties of carriages by design principle

There are several varieties divided into different groups:

Difference in the bottom bracket of a bicycle

They are connected using a thread: English, Italian, French. In addition, the sizes are distinguished: 68 mm, 73 mm, 83 mm, 100 mm. and etc.;

  • Eccentric fastening, based on fast scrolling of the carriage in the bicycle glass, after which it is fastened with bolts or nuts. The system is installed on vehicles with a planetary hub or fixed gear. Distinguish by diameter: landing (54 mm), standard (46 mm), BSA standard;
  • Press-Fit, used relatively recently. It has bearings hidden inside the carriage sleeve, into which an axle with a diameter of 30 mm is inserted. This method increases the reliability of the node. The division into types is carried out according to the diameters of the carriage glass.

What is a bicycle bottom bracket

The carriage assembly is located at the bottom of the frame, namely in the carriage glass. When a load is applied to the pedals, the bike moves. In addition to the force load on the carriage, dust and dirt contamination of the bearings is added due to the low position.

It is divided into collapsible and non-collapsible, but at the heart of all there are unchanged structural elements. According to which the bicycle carriage is classified as a mechanism that requires a special approach when choosing and installing. With its small size, it has a high cost and simple design:

  • The shaft or axis of the carriage is its moving core. It is located inside the body and has the shape of a cylinder. On the circles are connecting elements with connecting rods;
  • Body. the outer part of the bicycle carriage, on which the bearings are installed, the cups are placed, and the axis is placed inside;
  • The cups are the part connecting the bike glass to the bottom bracket. Depending on the variety, it can be screwed in or pressed into the glass of the frame;
  • The place where the connecting rods are connected is called the spline.

What to look for when choosing

Purchasing a new or replacing an old bicycle bottom bracket will require knowledge of some of the characteristics that may be required during the selection process. Prepare the following information if possible:

  • about the type and size of the carriage;
  • examine the carriage glass. If there is the necessary information in the passport, this will be the best option (type, size, etc.);
  • look at the chainline (this is a certain distance, parallel to the chain, which has an effect when the connecting rods and the shaft are coupled);


During maintenance, you will need a special tool that you will have to acquire if the replacement takes place at home. Special pullers and the disassembly process itself differ depending on the type of carriage assembly.

Before disassembling the carriage assembly, it is worth wiping the parts from dust and dirt. Next, start untwisting the left connecting rod, since the right side is more time consuming due to the presence of sprockets.

Certain types may have nuts that require a special wrench. You need to unwind carefully, without jumping off the tool, otherwise the edges of the parts will lick off.

Then, using a special key, insert it into the grooves and unscrew the cup on the left side. We take out the bearings from the assembly, remove the dirt inside and wash them in solvent, gasoline or any other degreaser. Then we lubricate them with bearing grease. The assembly is carried out in the reverse order, with the accompanying lubrication of the internal parts. Depending on the type of system, the process may take place slightly differently.

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The bike bottom bracket is not a large structural element, but deserves special attention as it can withstand high pedaling loads and provide a smooth ride for the wearer. Experienced cyclists, when choosing, highlight the importance of this detail and compare it to a shock absorber, which will seem ridiculous. However, understanding the bike and understanding its features of riding on a particular track, you can understand them.

bike, system

The choice of a bicycle carriage, like any other detail, requires a competent approach from the owner, which is often associated with experience, so an inexperienced person should carefully study the information available on this issue.


This attachment standard was created by Race Face as a response to the Octalink. It is slightly heavier than Shimanov’s design, but the splines work fully, providing the highest connection reliability. It is noteworthy that ISIS has an open industrial standard, that is, any manufacturer can freely produce such carriages without paying a percentage to the patent holder.

Both spline standards (Octalink and ISIS) are not compatible with each other. over, each of them has a differently designed bolt for attaching the connecting rod to the carriage axis.


In addition to the stars, other equipment can be attached depending on the conditions for riding the spider. For hard disciplines, instead of the outer star, the installation of rockring is characteristic. a plastic or metal pancake that takes all the blows of fate. In certain disciplines. downhill or dirt jumping. the system has only one star and is supplemented with a damper, the task of which is to keep the chain on the star under all conditions.

Leading Stars

For what they are intended, I think, there is no need to explain. Okay, I’ll tell you. They transfer the force from the spider crank pedals to the chain. Simple, right? Different materials are used in their production. steel, aluminum, composite, titanium. Even variations are possible: on budget bikes, some of the stars are made of aluminum, and some are made of steel.

The most commonly used ones are aluminum. Compared to steel, they are, firstly, lighter, and secondly, they are stronger in bending. The price, of course, is also higher, but the superiority of winged metal stars over steel stars is enormous. Steel, by the way, are different. There can be a chasm between stars made of this material: entry-level components are much softer than amateur-grade stars, and this directly affects switching clarity and resource.

In addition to materials, the stars differ in the shape and number of teeth. Some types of cycling use oval stars. Basically, there is only one such star in the system, since it is more difficult to switch when using this form. They need to be selected depending on the pedaling style of a particular athlete.

All stars, except for single-speed systems, that is, those that do not imply gear shifting, have a complex pattern of grooves, grooves and bumps. This is done to improve the switching quality. These elements guide the chain, help it move from star to star as accurately as possible. The teeth also have notches, some of them have a low profile, which helps the chain to go from a larger sprocket to a smaller one.

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There is a pin on the outer sprocket that prevents the chain from wedging between the connecting rod and the sprocket itself when the chain is dismounted. If it weren’t for him, if the chain got stuck, the bicycle would turn from a land vehicle into an air one. But the biker will not be able to fly for a long time, and the landing is unlikely to be soft and pleasant.

When installing stars on a spider, you should take into account their orientation relative to each other. To avoid any doubts, manufacturers have applied special marks. By lining them up in one line, you will install the set of stars correctly.

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We’re finally done with the shape, let’s move on to the number of teeth. The traditional combination for MTV is 44-32-22 and 48-36-24. There are other options, but the difference between neighboring stars should not exceed 12, and for road kits. 14. Otherwise, there is a high probability of fuzzy operation, jumping off and biting the chain. Who will love this? So experimentation is out of place here.

When choosing a system, you need to take into account the standard for attaching it to the carriage. Remember how Soviet bicycles had wedges in their cranks that loosened up all the time? Unfortunately, this design is still used on very cheap market bicycles, including domestic ones. This is one of the fastening standards, but it is hopelessly outdated, so we will not consider it. nerves are more expensive. Let’s dwell on the more modern standards of carriages and systems used today on bicycles.


The square is a monkey to analogy with Darwin’s theory of evolution, among the standards for fastening cartridge carriages. Old, but not yet obsolete. The advantages of such an attachment are low cost, acceptable level of reliability and ease of use. Often it is not recommended to assemble / disassemble the assembly, since the mount quickly renders the connecting rod seat unusable. In general, it provides a fairly strong connection. When a backlash appears, tighten the fixing bolt as soon as possible, otherwise you will have to change the connecting rod.


It is the link between the connecting rod and the stars. There are removable, non-removable and one-piece with a connecting rod. In some systems, its functions may be assigned to the first star of the system. On the market there are models of systems with a built-in power measurement sensor. This sensor is located just in the spider.

There are several design options. There are spiders designed for one, two, three, and even four stars. Currently, the most common spiders are three and two stars. Fastening type. from three to five legs.

If the stars are attached to the system with bolts (special bolts), then they can be changed if necessary. Such an opportunity is provided by high-level systems, while cheaper ones are made non-separable. the system changes only as a whole. The holes for attaching the stars (on each spider foot along the hole) are located in accordance with the BCD parameter. All manufacturers adhere to it.

Connecting rods

The cranks of the system are the levers that connect the pedal and the chainrings. Different materials are used in their manufacture. It can be steel, high-strength aluminum or carbon. Attempts were also made to use titanium, but such connecting rods were not widely used. But aluminum is the most popular. They are made by cold forging or milling.

The shape of the connecting rod is different. This is either a kind of channel, that is, a U-shaped sectional shape, or there is a cavity in the connecting rod, which makes it possible to lighten the structure without losing rigidity.

The connecting rod has a parameter such as length. It is measured between the centers of the pedal and carriage axes. The values ​​are standardized here, the values ​​are from 160 mm to 190 mm. Basic length. 170 mm. The length of the connecting rods should be selected depending on the rider’s height and riding style. It is logical that short cranks will be more convenient for short people, and longer ones for tall people. On bibs designed for extreme riding, it is preferable to use short cranks in order to increase the ground clearance. This reduces the likelihood of reaching the ground with the pedal when the suspension is fully deployed.

Integrated systems

This type of systems differs from the ones described above in that they also contain a carriage shaft, which is pressed into one of the connecting rods, mainly into the right one. The shaft is designed as a tube, that is, it is hollow, and has a larger diameter compared to traditional carriage shafts. Carriage cups in such systems are separate, with external industrial bearings. A plastic spacer is installed between the cups. The assembly algorithm is as follows: the cups are screwed into the frame together with the spacer, then a shaft is threaded through them and fixed with a bolt (bolts) of another connecting rod.

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This design is more advantageous in that due to the greater spacing of the bearings, such a design is stiffer, and the bearings themselves perform better. However, their wear is higher than bearings in carriages under a square.

There are several types of integrated systems. In addition to the standard (for MTB), an option is offered for road bikes with a bottom bracket length of 70 mm, and extreme bikes, due to increased loads requiring a more durable structure. the bottom bracket length on such bicycles is 83 mm.

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Separately, I would like to highlight the BB30 standard developed by Cannondale engineers. The connecting rod system here remains practically unchanged, the difference is that the bearings are not screwed into the frame, but pressed into it. Obviously, the frame must be designed for this. The carriage axis has an even larger diameter (30 mm) and the material is aluminum rather than steel. Even lighter and tougher.

The best part about buying an integrated system is that there are no compatibility issues. Cup sizes are the same regardless of carriage cup length or system model. The chainline will be correct anyway.


The system consists of the following components: two connecting rods, a spider and a chainring. Integrated systems also include an axis. Let’s dwell on each component in more detail.

Bicycle system device

A crankset (or “crankset” or “crankset” for short) refers to the mechanism that transfers power from the pedals to the chain. This is usually the third most expensive component on a bike (after the frame and fork) and has a pretty serious impact on the overall weight of the bike.

Materials (edit).

As for the materials, they directly depend on the price and use of the connecting rods.

The easiest in any discipline. steel. In more expensive models:

  • In mountainous and highways. aluminum and carbon (on pro-level bikes);
  • In extreme bikes, aluminum is supplemented (or replaced altogether) with chromium-molybdenum.

It is worth noting that aluminum connecting rods have almost completely replaced steel ones, even in the budget sector. Aluminum models often differ in design (cast, milled, hollow).

Always tighten the connecting rods well when installing. Poor tightening easily destroys even the most expensive models.

Mount types.

An important consideration when choosing a system is the type of carriage interface. Over the past years, the “square” has become the standard in the public sector. A more advanced (and more expensive) alternative is slotted interfaces, which are gradually becoming more available and are already found on lower models of bicycles of some manufacturers.

There are quite a few slotted standards (often each large manufacturer has its own standard), but there are also “general” ones, for example, ISIS. There are also systems with an integrated carriage. Today, this is the most modern type of fastening.


Consider a typical mountain bike crankset. It consists of:

  • Stars. There are steel (heavier and more durable) or aluminum (lighter, but less wear-resistant).
  • Star protection (optional). Protects clothing from grease and damage.
  • Fastening the stars. Rivets or studs (special bolts). If studs are installed, the stars can be changed as they wear out. Relevant in expensive systems with aluminum stars.
  • Legs. Stars are attached to them.
  • Carriage landing interface (read more below).
  • Connecting rods.
  • Place of attachment of pedals.

The left and right pedals have different threads. Do not mix them up when installing.

Types of stars.

In the middle and expensive segment, removable stars are used. This is true if you ride a lot and there is a possibility of wear on the stars (runs from 20 thousand km). The stars can be steel or aluminum. The former are heavier but more reliable, the latter are more suitable for sports bicycles. lighter but also less reliable.