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65-414: The term "bracket" refers to the tube fittings that are used to hold frame tubes together in lugged steel frames which also form the shell that contains the spindle and bearings; the term is now used for all frames, bracketed or not. There is some disagreement as to whether the word axle or spindle should be used in particular contexts. The distinction is based on whether the unit is stationary, as in

130-408: A bicycle is the distance between the pedal attachment points on the crank arms , when measured parallel to the bottom bracket axle. It may also be referred to as the " tread " of the crankset. The "Q" stands for "quack", a reference to the wide stance and waddling gait of ducks. The term was coined by Grant Petersen during his time at Bridgestone Bicycles . Q factor is a function of both

195-429: A mandrel , bending them to shape, and then welding the seams. These lugs are of constant thickness resulting in stress risers , if large amounts of file work are not done to alter the thickness of the lug. They are easily identified by the visible seam. Lugs used today on higher performance bicycles are investment cast (aka lost wax process). Copies of the lugs are made in wax, and they are attached together into

260-555: A "tree". The tree is surrounded by ceramic and fired in a kiln, thereby melting the wax and setting the ceramic. Finally, molten steel is poured in to produce the lug. Cast lugs have many advantages over stamped lugs: they allow much finer detail, tighter tolerances (and correspondingly less manipulation and file work), and more accurate angles, and they can be made from superior materials ( chromoly or stainless steel ). The disadvantages of cast lugs are few: casting doesn't allow for long points or cutouts (done for aesthetic appeal), it

325-589: A 100 mm (3.9 in) shell. Spindles come in a wider range of lengths (102–140 mm [4.0–5.5 in]), and are sized to match not only the shell width but also the type of crankset it will support (longer for triple, shorter for single, etc.). Spindle length, along with the crank's shape, determines the Q factor or tread. There are a few standard shell diameters (34.798–36 mm [1.3700–1.4173 in]) with associated thread pitches around 1 mm (24–28 TPI). Lugged steel frame construction Lugged steel frame construction

390-591: A 2-degree taper, there are two competing standards, defined by the measurement across the flat at the end of the spindle. The JIS size is used by Shimano and most other Asian manufacturers. The ISO size is primarily used by Campagnolo and other European manufacturers, in addition to cranks that adhere to the Nihon Jitensha Shinkokai (NJS) keirin standards (Sugino 75). Some manufacturers make cranks and bottom brackets to both specifications. Some square tapered bottom bracket axles are threaded at

455-509: A 50 mm bottom bracket notably used by Jan Ullrich in the 2003 Tour de France riding for Team Bianchi , and from 2004 to 2006 for T-Mobile Team . The bike also had a narrow rear hub spacing of 110 mm, which is 20 mm narrower than the 130 mm that was standard on road and time trial bikes at the time, resulting in the bike needing custom cranks and custom rear wheels. Narrow Walzer bikes are also said to have been owned by Michael Rich and Lance Armstrong , but for Armstrong

520-439: A bicycle frame, builders may use a small positioning structure called a jig to hold the tubes in place and maintain their precise alignment and frame geometry. Four lugs which may be used to construct a typical diamond frame include: The two rear dropouts (which join the seat stays to the chain stays, and hold the axle of the rear wheel ) may have integral lugs in some designs. The fork dropout or ends may be joined to

585-561: A broken tube can be removed by the application of heat to un-braze (known as sweating) its joints, enabling tube replacement. Steel frames generally are easier to repair than aluminium or exotic materials, and for this reason steel frames are preferred by many bicycle tourists , who often ride long distances in remote areas. Lugs also reinforce the joints, often resulting in a stronger frame, this gives lugged frames in particular an advantage for touring cyclists. Traditional stamped lugs (aka pressed lugs) are formed by pressing sheet steel over

650-423: A cartridge assembly. Independent of the type of bearing used, the cartridge often has some sealing to protect the assembly from the environment. Sealed cartridge bottom brackets are normally two pieces, a unit holding the spindle and bearings that screws into the bottom bracket shell from the drive side and a screw-in support cup (often made of light alloy or plastic) that supports the spindle and bearing assembly on

715-430: A crankset made for one standard into another. For example, a Shimano (two-piece Hollowtech II 24 mm outer diameter spindle) road crankset can fit into a BB30 bottom bracket shell (42 mm inner diameter) using aftermarket adapters. T47 is a size for bottom-brackets in 47mm with threads. This will account for enough room for an oversized axle, while also having enough room for big ball bearings, this in comparison to

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780-556: A hirth-like joint to form the spindle. Schlumpf makes a bottom bracket that incorporates a two-speed epicyclic transmission. As well as the different means to fit the bottom bracket into the frame, there are a number of ways of connecting the crank arms to the bottom bracket spindle. Shimano introduced a proprietary splined interface named "Octalink". Several other manufacturers (King Cycle Group, Truvativ, and Race Face) created an " open" standard called "ISIS Drive" or simply "ISIS", for International Splined Interface Standard. One of

845-399: A hub, or rotates, as in a bottom bracket. American bicycle mechanic and author Sheldon Brown uses axle once and spindle four times in his bottom bracket glossary entry. This article uses spindle throughout for consistency. Bottom brackets are available in several types, and can be split into whether they are assembled and disassembled with screw threads or whether they are pressed into

910-412: A later version that used solid, nutted spindles for improved reliability. In recent years Shimano has migrated much of their product line away from square taper to a spline attachment called Octalink and to external bearing types. In late 2006, Campagnolo announced that it was abandoning the square taper interface for double chainsets in favor of an outboard bearing design called Ultra-Torque , which uses

975-540: A letter or symbol code identifying the maker, and possibly the angle. From the late 19th century until the 1970s, this method of frame construction was favored because the lower temperatures of brazing (silver brazing in particular) had less of a negative impact on the tubing strength than high temperature welding , which can seriously weaken many steel alloys. Brazing thus allowed relatively thin walled, lightweight tubes to be used without loss of strength. However, recent advances in metallurgy have created steel tubing that

1040-490: A proprietary external bearing bottom bracket, oversized spindle and crank system. The design resembles the external bottom bracket designs marketed by FSA, RaceFace and Shimano. The modern versions used the same sealed bearing size (6805-RS, 25 mm inner diameter, 37 mm outer diameter) and the original mounting tool fits. The crank had intricately CNC machined wide hollow crank arms made of two halves glued together. However, Cannondale moved on from that system and developed

1105-759: A similar splined design to the Shimano bottom bracket. The difference is an 18-tooth versus a 20-tooth as per the Shimano design. Bottom brackets have several key size parameters: spindle length, shell width, and shell diameter. There are a few standard shell widths (68, 70, 73, 83, or 100 mm [2.7, 2.8, 2.9, 3.3, or 3.9 in]). Road bikes usually use 68 mm (2.7 in); Italian road bikes use 70 mm (2.8 in); Early model mountain bikes use 73 mm (2.9 in). Later models (1995 and newer) use 68 mm (2.7 in) more commonly. Some downhill bikes even use an 83 mm (3.3 in) bottom bracket shell. Snow bikes use

1170-613: A smaller bottom bracket shell. Frames with either Italian or English bottom bracket shell diameters (independent of threading) may be fitted with Thompson bottom brackets. Thompson bottom brackets are rare. The design is similar to a typical hub bearing and theoretically supports the load better but is hard to seal effectively against dirt and water. Since around the late 2000s, several designs with integrated bottom brackets with outboard bearings have emerged. The sales pitch of these systems have been to enable reduced weight and increased stiffness compared to internal bottom brackets. Because of

1235-409: A spindle either 19 mm or 19.05 mm (3/4″), 22 mm or 22.2 mm (7/8″), or 24 mm in diameter. The majority of newer or Asian parts are made to metric round numbers, and mixes of metric and non-metric (e.g. 19 mm and 19.05 mm) spindles and bearings may not be compatible, and can result in stuck parts. In some cases, the spindles are splined and the number of splines depends on

1300-403: A splined interface between spindle halves. Several different competing standards for splined interfaces exist. The tool drive for installing and removing these bottom brackets is often also a spline, instead of drives for regular hand tools. The Octalink system uses a spindle with eight splines. The splines provide a contact area between crank and spindle for an interface. Octalink exists in

1365-443: A steel cylinder with a slightly-modified bearing cup at each end. The cylinder, bearing and spindle are placed in the shell and held in place by the bearing cups, each of which has a narrow flange that bears against the edge of the shell. The Bayliss-Wiley Unit Bottom Bracket was introduced in the mid-1940s. It was fitted to various English lightweights through the 1950s and was used by Royal Enfield on its 'Revelation' small wheeler in

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1430-429: A wedge to match the spindle land. When tightened, this produces a simple and effective interface. The problem is that normally the interface cannot be tightened enough without a cotter pin press, a highly specialized type of clamping tool , though still produced and for sale. Cotters can also be installed with an improvised tool designed for another purpose, such as a ball joint splitter or hammer, with mixed results. All

1495-672: Is a method of building bicycle frames using steel tubing mated with socket-like sleeves, called lugs. For most of the bicycle's history , steel has been the primary material for bicycle frames, with lugged construction the primary assembling method. Steel continues in use by builders of high-quality steel frames, though its dominance as a frame material has waned since the mid-1990s displaced largely by aluminum and carbon fiber; lugging has been displaced by TIG welding . Lugged steel construction uses standard cylindrical steel tubes which are connected with lugs, external fittings made of pieces of steel (sometimes stainless steel ) which fit over

1560-420: Is attached to one of the crankarms, or at least a spindle which can be threaded through after the bearings have been mounted. Due to fixed spindle length and diameter, cranksets designed for one pressed standard may not be compatible with another. For example, a crankset made specifically for BB30 will not fit in a BB86 bottom bracket and frame. There are other instances where third-party adapters can be used to fit

1625-681: Is difficult to bend the lug to change the angle (requiring framebuilders to order lug sets that precisely match the desired frame geometry ), and they are more expensive. A relatively recent trend has been toward the use of stainless steel for investment cast lugs, as shown in the picture on the right. These lugs do not require painting, but must be brazed using silver filler rod, which necessitates much better heat control and better fit of lug to tube. Cast lugs are found on higher quality production bikes, and virtually all custom bikes now made; stamped lugs are found on less expensive production bikes, and older custom bikes. Lugs are usually stamped with

1690-604: Is more like a traditional bottom bracket in that the spindle is not permanently pressed into the right crank. Again, the Howitzer spline looks similar to the ISIS Drive standard spline but is actually different, so as to prevent the usage of ISIS Drive cranks on the external bearing bottom bracket, which would affect chainline and Q-factor. In late 2006, Campagnolo introduced an outboard bearing design called Ultra-Torque, which has both crank arms permanently attached to halves of

1755-433: Is not adversely affected (or may even be improved) by high temperature welding. This has allowed both TIG and MIG welding to displace lugged steel construction, in large part because these methods lend themselves more easily to automation and reduce the cost by eliminating the lugs. Conversely, lugged steel construction remains popular among builders of custom-fit bicycle frames, and among amateur framebuilders, since it

1820-526: Is one of the simplest methods of constructing a bicycle frame by hand in a small workshop. Despite the fact that lugged steel frames are no longer mass-produced, frames are still available. There is a trade of used bicycles in North America, especially in large cities and college towns . Because of their durable construction, many lugged steel frames from the 1980s, 1970s, and earlier remain in usable condition. Japanese- and French-made frames from

1885-555: Is that assembly and disassembly of press-fit bottom bracket bearings require expensive special equipment. Some hobby-mechanics assemble and disassemble themselves using simple hand-tools, but there is a certain risk that the frame may become damaged. Another disadvantage is that many users report that they start to creak after a certain time. A third disadvantage is that there has become a wealth of competing and incompatible press-fit bottom bracket standards introduced by various bicycle manufacturers. The current pressed-bearing standards (and

1950-408: The bike boom are particularly common in North America. These range widely in quality: low-end frames are made of ordinary high-tensile steel using thick, heavy tubing and stamped steel dropouts. Better frames are nearly always made of some variant of chromoly steel alloy and include forged or investment-cast dropouts. Higher-end frames are often made of butted steel tubing, which is thicker at

2015-495: The SI cranks and the new BB30 unthreaded press-fit bottom bracket standard. BB30 requires special frames which have a 42 mm diameter unthreaded bottom bracket shell (which is larger than the 34.9 mm threaded ISO standard threads) allowing use of internal sealed bearings while their top level SI crankarms are still two machined aluminum halves glued together. Another precursor of the current external bearings/through spindle design

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2080-412: The bearing balls, reinstalling the spindle, and adjusting the cups. The design is nowadays mostly found on affordable bikes due to its simple and affordable design, and is also an easily serviceable design. The Bayliss Wiley unit bottom bracket is a self-contained unit that fits into a plain, slightly larger-than-usual bottom bracket shell in a bicycle frame. It comprises a standard spindle and bearings in

2145-402: The bottom bracket shell. Since the 2000s and especially the 2010s, a lack of standardization, or rather the constant introduction of new standards that disappear after relatively short periods, has been described as a complex topic to deal with for those who want to buy bicycle components or maintain bicycles. Many bicycle brands have introduced their own dimensions for bottom bracket bearings, and

2210-421: The bottom bracket unit being a pre-mounted assembly containing the spindle (or axle) as well as its bearings, as opposed to them being separate parts which must be mounted separately. Cartridge hence refers to the functional assembly unit, and does not indicate what type of bearings the cartridge utilizes. Either loose ball bearings (adjustable cup and cones), sealed bearings or other types of bearings may be used in

2275-419: The bottom bracket width (axle length) and the cranks. Bottom brackets axles vary in length from 102mm to 127mm. Mountain bike cranks are typically about 20mm wider than road cranks. A larger Q factor (wider tread) will mean less cornering clearance (while pedaling) for the same bottom bracket height and crank length . A smaller Q factor (narrower tread) is desirable on faired recumbent bicycles because then

2340-468: The corporations marketing the systems. These external bearings are compatible with those from other manufacturers. With this new standard have come several cranksets designed to use the external bearings of other manufacturers, such as DMR's "Ex type" and Charge Bikes "Regular" cranks. In the early 1990s at Magic Motorcycle, a small USA component manufacturer later purchased by Cannondale, and re-formed into Cannondale's CODA brand (Coda Magic 900 cranks), made

2405-560: The deeper-grooved v2. The system is proprietary and protected by Shimano patents and license fees. ISIS Drive, the International Splined Interface Standard, is a non-proprietary splined specification for the interface between a bicycle crankset and the bottom bracket spindle. It was created by King Cycle Group, Truvativ, and Race Face. ISIS Drive is open source and free to the public to be used as seen fit. BMX 3-Piece bottom brackets typically use

2470-451: The different use of terminology by the various manufacturers has been described as confusing. An old American term for the bottom bracket is hanger . This is usually used in connection with Ashtabula cranks, alternatively termed one-piece cranks. In typical modern utility bikes, the bottom bracket spindle is separate from the cranks. This is known as a three-piece crankset (spindle, left crank-arm and right crank-arm). The cranks attach to

2535-429: The driveside (right) crankarm and the bottom bracket spindle are an integrated unit and the bearing cups are placed outside of the bottom bracket shell, threaded into the bottom bracket shell. There are a number of versions of this design available: Shimano's Hollowtech II, RaceFace's X-type, FSA's MegaExo. The terms 'X-Type' and 'Hollowtech II' are both used to refer to any design of this type, but are in fact trademarks of

2600-406: The earliest standards of crank interface, 'cottered cranks are now considered obsolete in developed countries, but are still in common use in developing nations. The spindle is a cylinder and has a flat region across it (a land). The crank has a hole through it to fit onto the spindle, with a transverse hole for the cotter pin. The cotter pin is cylindrical with one side flattened at an angle to form

2665-462: The elements and easily contaminated, although this rarely causes failure. Ball retainers (caged bearings) are used to facilitate assembly and to reduce the number of balls required. The Thompson bottom bracket uses adjustable spindle cones and cups pressed into the bottom bracket shell like the Ashtabula bottom bracket. Unlike the Ashtabula crank, the non-drive side crank is removable, allowing for

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2730-448: The end of the lug. At increased expense, frames may have lugs which are cut and filed by hand into fancy shapes, both for slight weight savings and as a display of craftsmanship. In addition many frame builders file the lugs to thin them, in order to reduce stress concentrations. These ornate or fancy lugs may be painted to accentuate their appearance. Lugged steel frame can be repaired more easily than MIG or TIG welded steel frames;

2795-543: The ends and thinner in the middle, reducing weight but increasing the cost. New lugged frames are manufactured, often to custom geometry from a number of speciality manufacturers. The utility bicycles manufactured in large quantities in China and India , (such as the Flying Pigeon ) and exported to countries in the region, are made from lugged steel. Q factor (bicycles) The Q factor or quack factor of

2860-464: The ends and use nuts. Other square tapered bottom brackets are hollow, allowing for crank bolts to thread into the ends. Titanium has been used in an effort to make bottom brackets lighter, but early attempts were not entirely successful. Several manufacturers have built bottom brackets with titanium spindles and alloy cups but their durability was lower than that of steel. Early Campagnolo Super Record titanium spindles (which were hollow) were replaced by

2925-422: The ends of the tubing. Before assembly, the builder cuts the tubes to the desired length and precisely mitres their ends, providing a tight fit. The end of the tubes are inserted into the lugs and subsequently brazed with a silver or brass filler metal. The lug greatly increases the strength of the joint by distributing the molten filler metal over a larger surface area via capillary action . When brazing

2990-524: The fairing can also be narrower, hence smaller and lighter. Sheldon Brown said that a narrower tread is ergonomically superior because it more closely matches the nearly-inline track of human footsteps. Research from the University of Birmingham in the United Kingdom suggests narrower Q factors are more efficient, likely due to improved application of force during the pedal stroke, as well

3055-403: The fork blades using a similar method as well. The fork crown, which joins the steering tube to the fork blades, may have either an external or internal socket design. In most lugged steel frames, the lugs have a simple pointed shape. The lug's curves maximize the strength of the joint, while minimizing the possibility of stress risers , which would otherwise make the frame prone to cracking at

3120-446: The ingress of water and dirt. The early Shimano LP bottom brackets from the 1990s had the support cup on the drive side and used loose bearings inside; they could be dismantled and serviced much like adjustable cup and cone bearings. [1] In general use, the term 'three piece' refers to the former design, with sealed bottom brackets being seen as the 'standard'. Designs utilizing separate bearings are usually found on low end bikes, due to

3185-400: The load is on one very small area of the cotter pin and the crank land, the cotter pin deforms plastically under normal use and must therefore be replaced regularly. If this is not done the crank and the spindle wear and must be replaced. The rider will get a warning through a characteristic creak sound that aging pins cause the cranks to make. Previously referred to as 'cotterless', since this

3250-649: The low cost. With a one-piece (also called Ashtabula) crank and bottom bracket, the spindle and crank arms are a single piece. The bottom bracket shell is large to accommodate removal of this S-shaped crank. Bearing cups are pressed into the bottom bracket shell. The crank holds the cones, facing in; adjustment is made via the left-threaded non-drive side cone. One-piece cranks are easily maintained and reliable, but heavy. They are found on BMX bikes as well as children's bicycles and low-end road and mountain bikes. They fit only frames with American sized (also known as "Pro size") bottom brackets. The bearings are normally open to

3315-427: The manufacturer/model of the crankset, or in other cases, the spindle is specific to the crankset. There are other designs in use that have varying degrees of popularity. One is Truvativ 's PowerSpline interface. It is a 12-spline spindle proprietary to Truvativ offered as a lower cost alternative to other spline designs. It is essentially a beefed-up square taper spindle with splines instead of tapers. Phil Wood uses

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3380-453: The manufacturers who developed them) are: In the BB30 (Cannondale), BB90 and BB95 (Trek) systems, the bearings are pressed directly into the frame. For PF30 (SRAM), BB86 and BB92 (Shimano), BB79 (Cervelo), and BB386EVO (FSA) the bearing is housed in a nylon plastic cup that is pressed into the frame’s bottom bracket shell. Pressed-in standards usually require two-piece cranksets where the spindle

3445-403: The marketplace in two variants Octalink v1 and Octalink v2, and the two are not compatible with each other. The difference between the two can be seen by the depth of mounting grooves on the bottom bracket spindle. v1 spline grooves are 5 mm long, while v2 grooves are 9 mm long. Shimano 105, Ultegra 6500 and Dura Ace 7700 cranksets mate to v1 spindles, while later mountain bike designs use

3510-415: The mid-1960s. However, the unit bottom bracket was never popular and it had a reputation for being troublesome. A lack of positive location allowed it to rotate within the frame, loosening the bearing cups. Contemporary users overcome the problem by fixing the unit in the frame using adhesive or a screw. Many modern bicycles use what is called a "cartridge" bottom bracket instead. "Cartridge" here refers to

3575-402: The non-drive side. Other designs are three piece, the spindle is separate, but the bearing cups incorporate cheaply replaceable pairs of standard industrial sealed bearings. Either arrangement makes servicing the bottom bracket a simple matter of removing the old cartridge from the bottom bracket shell, and installing a new one in its place. Cartridge bottom brackets generally have seals to prevent

3640-407: The potential for reduced knee variability and risk of injury. "Old Faithful" was a homebuilt bike that Graeme Obree famously used in 1993 to 1995 at his attempts at the hour record , which had a very narrow bottom bracket measuring only 40 mm wide, and famously also used " washing machine " bearings. Walser model 5 designed by Andy Walzer from Switzerland was a narrow time trial bike with

3705-543: The relatively small 1.37″ (34.9 mm for ISO, or 36 mm for shells threaded to the Italian standard) diameter shell, designs that place the bearings inside the shell can either have large bearings and a thinner spindle, which lacks stiffness, or smaller bearings and a thicker spindle (such as the original Shimano Octalink), which lacks durability. External bearings allow for a large diameter (hence stiff) and hollow (hence light) spindle. They also offer more distance between

3770-445: The right crank. The left side spline interface looks similar, but is different so as to prevent installation of older ISIS Drive crankarms—which are no longer compatible because Q-factor and chain line cannot be maintained using these older cranks with an external bearing bottom bracket. Truvativ refer to this design as 'Giga-X-Pipe' or 'GXP.' They also make a heavier duty external bearing bottom bracket called 'Howitzer.' The Howitzer BB

3835-400: The right-side bearing being internal inside the bottom bracket shell, and the left-side bearing being external (and having the 6805-RS sealed bearing, too). Giga-X-Pipe was Truvativ's (later bought by SRAM in 2004) approach, and is an evolution of the ISIS Drive bottom bracket, but with a longer spindle and the bearings outside the bottom bracket shell. The spindle is permanently pressed into

3900-444: The spindle (called semi-axles), which then join in the middle of the bottom bracket with a Hirth joint and a bolt. Bicycle frames utilizing pressed bearing standards do not have any threads inside the bottom bracket shell. The bottom bracket is pressed directly into the frame. Using pressed in standards allows frame manufacturers greater flexibility in the frame design, and can offer greater stiffness and reduced mass. A disadvantage

3965-415: The spindle via a common square taper, cotter or splined interface. Earlier three-piece cranks consist of a spindle incorporating bearing cones (facing out), a fixed cup on the drive side (with a cone), an adjustable cup on the non-drive side (also with a cone), and loose bearing balls (or held by a cage). Overhauling requires removing at least one cup, cleaning the cups, cleaning or (more usually) replacing

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4030-408: The traditional BSA in 34.6mm. A bottom-bracket made for 46mm pressfit can be threaded up to a fit for a 47mm bottom-bracket and will have approximately a 46mm inside diameter. The T47 standard had a shell width of 68mm. The T47a has a width of 77mm. The T47i has a width of 86.5mm. Lightning Cycle Dynamics, Inc. offers a carbon crank bottom bracket assembly with semi-axles that connect in the middle via

4095-459: The two bearing surfaces, which contributes to stiffness while allowing lighter components (but also may increase the Q factor ). A different approach than to move to threaded external bearings could be to standardize on one of the larger diameter press-fit BMX shell standards for all bicycles, or the press-fit BB30 standard originally introduced by Cannondale. Several implementations of external bearings have been brought to market. In one design,

4160-409: Was developed by Sweet Parts, a micro-manufacturer of high end cranks and stems. Their Sweet Wings cranks from the early 1990s incorporated the through spindle concept by attaching the two half pipes coming off each crank arm and held together with a single bolt that resided within the cavity of the spindle itself. Their bottom bracket bearing arrangement was a hybrid internal/external bottom bracket, with

4225-472: Was the design that was introduced after cottered spindles, square taper was once the most popular (and only) style 'cotterless' crank. This interface consists of a spindle with square tapered ends that fit into square tapered holes in each crank. It is still manufactured in great numbers for bicycles and maintains popularity for such applications as bicycles. Not all square taper crank and bottom bracket combinations are compatible. Although nearly all spindles use

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