How to properly install bearings in a bicycle bottom bracket


The carriage of a road bike, and indeed of any other bicycle, is perhaps its most loaded mechanism. Therefore, in carriages with external tapered bearings at moments of significant overloads, bearing cages are often destroyed, and the ball tracks on the cones of the carriage shaft are often damaged.

Intensive wear of the tracks also occurs when the bicycle is used on unpaved roads due to the ingress of dust into the carriage assembly. The easiest way to restore the mechanism to work is to replace damaged parts or assembly. This is usually done in repair shops. But such a solution is hardly acceptable for a zealous home-builder who will try to bring the regular parts back to life.

He will groove the carriage shaft to a diameter of 15 mm for almost the entire length, leaving only a place on one edge for installing a connecting rod with a drive sprocket. This dimension corresponds to the diameter of the inner bore of bearings of the 202 series. On the shaft until it stops against the shoulder, it will push a 60202 bearing with a protective washer outward (it is possible to use bearings of the 80202 type with protective washers on both sides).

The shaft will insert into the carriage body and press the bearing there flush with the ends, if necessary, slightly bore the threaded part inside the body pipe to the outer diameter of the outer ring. Then, on the other hand, it will push it onto the shaft and press it into the housing with the second bearing with a protective washer outward.

Next, he will grind the adapter sleeve for installing the connecting rod, cutting a groove in it for the mounting wedge and press it onto the protruding end of the shaft. The carriage mechanism repaired in this way often works until the bicycle is “written off”, but too much has to be machined, cutting off the entire cemented layer of the shaft, and the flat of the groove for the wedge remains very small. The connecting rod on this side can loosen from heavy loads, and then you have to think about how to repair this place too.

But the most undesirable thing with this repair method is that the special thread SPM 35×1 (on the one hand. right, and on the other. left) inside the carriage body will almost certainly be damaged, and the unit will become unrepairable. Therefore, I acted a little differently, although it was also not without turning work.

I pierced shallow grooves with a radius of 4 mm for balls with a diameter of 8 mm (more precisely, 7.94 mm) on the damaged tracks of the cones of the carriage shaft in such a way that the diameter of the journal of the shaft under the grooves was 14 mm. I took the balls from two old bearings 204. I ground the grooves, although this could not have been done. the balls themselves are able to align and even strengthen the tracks. The node was assembled in this sequence.

First, having thickly smeared the groove on one side of the shaft with grease, he drowned the balls in grease one to one and put the cup on the shaft and balls. The shaft was inserted into the carriage body and screwed in the cup all the way. I did the same on the other end of the shaft (on the opposite side of the carriage), screwing in the second cup until the shaft in the body began to rotate without play, but freely.

Instead of balls from bearings 204, you can take from 203. Their balls with a diameter of 7.14 mm are installed on the shaft on each side, nine pieces. But the grooves on the shaft need to be machined with a radius of 3.6 mm, leaving the journal on the shaft with a diameter of 15 mm.

The first way to repair bike carriages. I. shaft; 2. bearings 60202 (80202); 3. bushing; 4. carriage body

Installing the connecting rod on the shaft through the adapter sleeve: 1. shaft; 2. connecting rod; 3. bushing; 4. wedge; 5. washer; 6. nut

Modification of the carriage shaft according to the second repair method (the radius of the groove and the diameter of the journal for balls with a diameter of 7.14 mm from bearings 203 are indicated in parentheses)

Repaired carriage assembly assembled: 1. left connecting rod; 2. shaft; 3. lock nut; 4. left cup; 5. balls from bearings 204; 6. carriage body; 7. right cup; 8. leading sprocket; 9. the right connecting rod

Types of carriage assemblies.

All carriages can be divided into open and closed, so called cartridges or capsules. Sometimes you can also find half-cartridges. In the first case, the shaft rotates in bearings installed in cups, which in turn are screwed into the carriage tube of the frame. Disadvantages of this type of carriage. the need for precise manufacturing of the frame to avoid distortions and the complexity of organizing high-quality protection of bearings from the external environment.

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The bottom bracket cartridge avoids these problems: the bearings are housed in a rigid housing that screws into the bike frame. This eliminates misalignment of the bearings and the need to adjust the carriage. A good quality shaft seal can be conveniently accommodated in the cartridge. In addition, the bearings will be protected from rust, which can crumble from the inside of the frame tubes. Most cartridges are non-collapsible, but some are collapsible, such as the inexpensive Shimano cartridges. It is advisable to choose cartridges with a chrome-plated outer coating (for example, Shimano Deore LX and above) and lubricate generously to avoid sticking to the frame.

At the same time, one cannot say: open carriage. bad cartridge. OK. For example, if dirt gets into the open carriage, it can be cleaned and collected with new grease, while the cartridge will quickly wear out and fail under such conditions.

Bicycle bottom bracket (bottom bracket)

The bottom bracket is a bearing assembly that rotates the cranks with pedals and sprockets relative to the bicycle frame. The purpose of the carriage assembly. transfer torque from the pedals to the bicycle wheel with minimal losses. The location at the bottom of the frame, directly behind the front wheel, leads to its constant throwing of dirt and water, therefore, the carriage bearings must be well protected from the external environment.

Types of carriage shaft connections with connecting rods.

On very cheap bicycles of unknown make, you can often find carriages in which the carriage shaft and connecting rods are a single piece. Such disposable carriages do not hold up to scrutiny.

For bicycles of Soviet and Russian production, the connection of the carriage shaft and connecting rods with a key (wedge) is characteristic. In the existing version. an unreliable design that often looses if the key was not screwed in properly before the first ride (and on new bicycles it is very often loosely screwed in). The only advantage of this type of connection lies in the possibility of fairly easy removal of the connecting rods without special pullers.

Most imported bicycles use a square crank connection. The ends of the shaft in such carriages are made in the form of a square cone. The connection turns out to be very rigid and does not loosen over time, since the main load goes to the shaft itself, and not to the key, as in the previous type. The shaft and connecting rod are bolted together with a 15mm open-end or 8mm Allen key on the cheapest BBs such as the Shimano Tourney. the connecting rod is secured with a nut. In this case, you have to use a special puller to remove the connecting rods.

advanced bicycles, both mountain and road, now use a splined connection of the crank shaft and connecting rods. There are two standards: Shimano OctaLink. which is only used by Shimano in Deore groups. XTR. and, introduced in 2000 (due to licensing requirements from Shimano) ISIS Drive. backed by well-known companies like Bontrager. Chris King. FSA. Race Face. Stronglight. Truvativ. Both types of connections are incompatible due to the different number of splines and their configuration. The spline connection allows you to achieve even greater rigidity than a square one, and also to use large diameter hollow shafts in the carriages to reduce weight and increase the rigidity of the latter.

Carriage dimensions.

When installing the carriage, consider the following dimensions: bottom bracket shell, right flange type, axle length and chain line parameter.

The carriage tube width can be one of three sizes: 68 or 73 mm BSA type or 70 mm Italian type. In addition to dimensions, the third type also differs in threads. The most common are the first two standard sizes, and there are also the so-called E-type carriages with an enlarged rim on the right side for attaching the front gear derailleur.

The length of the carriage shaft, in combination with the use of a specific system, determines at what distance the stars of the system will be relative to the center plane of the bicycle frame (parameter chain line). Typical values. 47.5 and 50 mm. Typical shaft lengths for splined connections. 113 and 118 mm, and there are a lot of them for a square: from 116-127 for Shimano Tourney, 116 for Shimano Altus to 108-113 for higher groups.

It is sometimes necessary to repair the carriage of a bicycle. An unpleasant crunch appeared in the carriage. it is imperative to pay attention to it. If the carriage fails, then replacing it for an uninformed user and non-specialist at home is a difficult task, here we are talking about a modern mountain bike.

Carriage with thrust sleeves and bearings

To remove the pedal connecting rods, you will need a special socket wrench and a special squeezing of the connecting rod from the carriage axis.

A crackle in the carriage, which means in the bearing, indicates that it is necessary to change, and it is necessary. The bearings themselves are protected against dust and moisture and cannot be repaired, only replaced. It is necessary to disassemble the carriage.

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Unscrewing the thrust sleeve on the frame, which closes the carriage, is also difficult, if not impossible, without a special key. The replacement of the carriage itself, together with the bearings, will not cause difficulties, only the removal of the carriage.

There are enough types of carriages, but in principle they are the same on modern bicycles. We can only say that the most durable are sealed bearings, and the lightest ones on the move are their bulk balls. My bike has bearings.

If you have all of the listed keys and a new bottom bracket specifically for your bike, then we proceed to replace the bottom bracket. First, remove the plastic plugs from the pedal cranks at the ends of the carriage axis with a simple screwdriver. The next action with a socket wrench is to unscrew the connecting rod tightening bolts.

Some of the cranks have a triangular seat on the axle, I have a square seat on my bike with a variable square thickness to the frame. This must be taken into account when buying a new replacement unit. At the triangular cross-sectional axis of the carriage, there is also a gradual thickening of the axis towards the frame, so the connecting rod is tightened very tightly with this bolt and to remove the connecting rod, a squeeze will be needed. For her, a fine thread is cut in the connecting rod. We turn out the pusher almost to the end and screw the squeeze into the connecting rod. We screw in the pusher and the connecting rod, together with the squeeze, should come off.

Carefully remove it from the axle and wipe the boot from dust and dirt. Access is opened for removing the thrust sleeve of the carriage. Here again you need a special key. It is necessary to take into account the direction of the thread on the sleeve when removing it. on the right side of the bike, it turns clockwise, and on the left side of the bike, counterclockwise. Insert a special key into the slots under it and unscrew the thrust sleeve with an adjustable wrench or a suitable size.

Only now we remove the connecting rod from the other side of the bike in exactly the same way as described earlier. Remove and clean the boot on the other side of the carriage. We take out the carriage and throw it away mercilessly. If you have the opportunity to get exactly the same bearings on the carriage, then you can simply replace them, they can be easily removed and replaced. The bearing number can be found on the bearing itself. The cost of the carriage assembly for me is the lesser evil for the price and the hassle with getting the bearings, so I just pulled out the carriage and used it elsewhere. swivel mechanism for the TV antenna. I changed everything to new.

properly, install, bearings, bicycle, bottom

It is assembled in the reverse order, no special settings are required, you just need to tighten it better. Be careful when installing the anthers, do not damage them, they are installed in the groove of the thrust sleeve of the carriage.


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How to replace and repair a bearing in a bicycle bottom bracket?

Absolutely all mechanisms wear out after a certain time, as they are subject to external environmental factors. They require service, repair, or complete replacement with a new part.

To make sure what actions need to be taken, you will definitely have to remove the bike carriage, figure out which parts have become unusable, and then make a decision: make repairs or make a complete replacement.

Open carriage

The latter, in turn, are screwed directly into the bottom bracket of the bicycle frame. This type of carriage is serviceable and can be easily removed, lubricated, sorted out and reassembled. If necessary, it can also be replaced with a new one.

Maintenance of a bicycle carriage means disassembly, lubrication of its parts, installation and adjustment.

Bearing types

Bearings are support devices for the moving parts of a bicycle. They hold the parts in place and help the mechanism to function properly, making the pedals rotate smoothly, for example. The rest of the components of the bicycle structure work in the same way.

Since bearings on a bicycle can be in different places, the principle of their operation is different, which means that before changing them, you need to know what types of this product are. They are divided into three types:

  • Ceramic;
  • Plain bearings;
  • Rolling bearings.

Let’s dwell on the extreme option. In total, two types of rolling bearings are used for a bicycle: a cone-cup (or bulk) and non-separable, which are called “cartridge”.

Bulk consists of a set of balls and a cup built into the bike. Cartridge are two rings with balls. They do not need adjustment, since such bearings just need to be changed if the need arises.

Non-separable carriage service

If problems arise with a carriage of this type, it is replaced. When choosing a new carriage, it is important to know the length and width of the shaft, as well as the type of connection with the connecting rods.

  • Start by loosening the locknut. Tighten the adjusting cone counterclockwise until it rests against the bearing, then unscrew it 1/4 turn back.
  • Tighten the lock nut.
  • Grasp the connecting rod and wiggle it to check for any play. If present, loosen the lock nut and slightly tighten the adjusting cone. Re-tighten the lock nut and check again.
  • Repeat the process of checking and tightening the cone until you feel any looseness.
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Replacing Bearings In A Bottom Bracket

Note: In one-piece systems, the bearings are not carefully polished. Slight adjustment error is possible. Adjust the bearings to ensure free play, but no backlash

How to disassemble and remove the bicycle carriage yourself

Perhaps lovers of simple periodic bike reels are not familiar with this term, but those who often use a bicycle as a vehicle, and even more so, professionals in the field of cycling, are aware of what a bottom bracket mechanism is.

Like any mechanism, this part over time is exposed to external influences, wears out or completely becomes unusable, which requires maintenance, full or partial replacement. In any case, you first need to remove the carriage, establish the suitability of the part, and then decide whether to repair it or replace it with a new one.

Troubleshooting: maintenance, cleaning, replacement

Dismantled the carriage, pulled it out of the frame and what do we see? The condition of the bottom bracket depends on how much dirt gets into it and how much the bearings are worn out. Sometimes the bearings simply shatter and require a complete replacement. This often happens if the carriage assembly has been in operation for more than three to five years.

First, all parts must be checked for defects. This primarily applies to bearings. Then we inspect the carriages, cups with latches. If any component has visible damage, then you need to change it to a new one. The rest of the parts are cleaned in a solvent. The most difficult thing will be to clean the bearings: dirt is very firmly adhered between the balls.

The space inside the carriage glass is cleaned with a rag. It is better to sprinkle fine dirt with a lubricating spray (WD-40, for example) and wipe the walls with a soft dry cloth.

Required tools

Intensive use of transport leads to the fact that the structure is regularly exposed to external factors. In this regard, rust appears on the surface of the parts, mechanical damage is possible. You can eliminate negative signs with the help of systematic, competent maintenance of the bicycle carriage.

Any mechanism, regardless of type, is installed in a special glass. That is why, in order to carry out repair work, it is required to dismantle it. This procedure must be carried out in an equipped room using suitable equipment. If a breakdown occurs on the road, you can remove the carriage using a standard set of tools. You will need:

  • wrenches with optimal sizes and shapes;
  • squeeze for the connecting rod;
  • flat head screwdriver;
  • pullers for pressing out bearings;
  • small light hammer.

Beforehand, it is recommended to thoroughly wash all the elements of the bike, which will greatly facilitate the work. The frame must be securely fastened to reduce the risk of injury. Dismantling is carried out in accordance with the instructions of the manufacturer indicated in the technical documentation.

properly, install, bearings, bicycle, bottom

How To Remove And Install External Bearing Bottom Brackets By Performance Bicycle

Despite the variety of tools required, the process of removing and disassembling the carriage on a bicycle is the same, regardless of the type of mechanism. The main thing is not to forget that the left-hand thread is used on the right side.

Wrenches Connecting rod extractor Flat head screwdriver Bearing pullers

Ball bearing carriage lubrication

It should be noted that carriages of this type are short-lived, so maintenance and adjustment of bearings should be carried out quite often.

How to troubleshoot

The machine will last longer if it is properly cared for. The carriage is replaced for various reasons:

  • seasonal maintenance consisting of cleaning, lubrication, bulkhead;
  • elimination of backlash;
  • tight turning of the axis;
  • jamming of the mechanism;
  • the appearance of extraneous sounds in the pedals when the device is operating.

The first warning signs of damage to the rear carriage are characteristic sounds. A squeak occurs when there is insufficient lubrication, a crunch occurs when dirt gets into the bearings. In the presence of such features, the mechanism is analyzed.

It is impossible to visually determine the malfunction; problems appear only while driving. Even minor breakdowns do not allow full acceleration, cause difficulties when turning the pedals. Repair of the bicycle carriage will be required if there are backlashes, which indicate bearing wear, axle misalignment.

How To Overhaul A Bike Bottom Bracket. Remove/Clean/Install New Bearings

In some cases, the “standing ride” method is used to diagnose problems. To do this, you need to gain high speed, then stand up, leaning on the pedals. If there is a loud cracking noise, noise, the bicycle carriage will have to be replaced or repaired.