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93-449: Starting times are at equal intervals, usually one or two minutes apart. The starting sequence is usually based on the finishing times in preceding races (or preceding stages in the case of a multi-stage race) with the highest ranked cyclist starting last. Starting later gives the racer the advantage of knowing what time they need to beat (and also makes the event more interesting to spectators). Competitors are not permitted to draft (ride in

186-591: 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

279-463: A España Fastest Tour de France Time Trial longer of up to 20 km Fastest Tour de France Time Trial longer of up to 40 km Fastest Vuelta a España Time Trial longer than 20 km Fastest Non-Prologue Stage of Giro d'Italia [REDACTED] Media related to Individual time trial at Wikimedia Commons Drafting (racing) Drafting or slipstreaming is an aerodynamic technique where two moving objects are aligning in

372-408: 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 the bottom bracket shell. Since

465-423: 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

558-492: A close group to exploit the lead object's slipstream and thus reduce the overall effect of drag . Especially when high speeds are involved, as in motor racing and cycling, drafting can significantly reduce the paceline 's average energy expenditure and can even slightly reduce the energy expenditure of the lead vehicle. Drafting is used to reduce wind resistance and is seen most commonly in bicycle racing , motorcycle racing , car racing , and speedskating , though drafting

651-430: 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

744-475: A final individual time trial in Madrid in which the winner is often decided, providing much drama and excitement at the end of the stage race. In recent years, Óscar Sevilla and Roberto Heras have seen their lead evaporate in the time trial in Madrid. The Grand Prix des Nations was a semi- Classic event; professionals may also compete in the annual World time trial championship . The individual time trial

837-559: 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

930-412: 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

1023-738: A line of cars could sustain higher speeds and/or use less fuel (resulting in fewer pit-stops) than a single car running by itself. In recent years, as aerodynamics have become increasingly critical to the performance of stock cars on "intermediate" oval tracks (between 1.33 and 2 mi) and superspeedways not requiring restrictor plates (such as the Indianapolis Motor Speedway ), the effect of turbulent, or "dirty", air when following closely behind another car has become much more akin to that described above in open-wheel racing (a situation described in NASCAR circles as aero push ), and

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1116-490: A much better aerodynamic position. They were first brought into the time trialling public eye in the 1989 Tour de France when Greg LeMond overcame a 50-second deficit in the final day's time trial to win the Tour by 8 seconds from Frenchman Laurent Fignon . Fignon was using conventional handlebars, Lemond the new triathlon style. The concept has changed little since then, with only Scotsman Graeme Obree attempting to improve

1209-490: 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

1302-466: A race is called a peloton where cyclists ride in a long formation with each (but not the first rider) drafting behind the others before them. When cyclists ride fast they form a paceline . Each cyclist, except the first, is drafting behind another one. In order to ride very fast, a team of some skilled cyclists may form the "Belgian tourniquet". Successively, each cyclist leads the group. Drafting can be cooperative : several competitors take turns in

1395-556: A result, passing is often the result of cooperation between two or more drivers or is achieved by sucking air off the side of the car being passed, a technique called side-drafting. Bump drafting is a tactic used at Talladega and Daytona. The technique was initially popularized by the Archer Brothers in the SCCA Sportruck series during the late 1980s. It begins as normal drafting, but the following car pulls up behind

1488-759: 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

1581-614: 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

1674-410: 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

1767-403: 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

1860-444: 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

1953-586: A team car carrying coaches and spare parts, but the cyclists are not permitted to draft behind the vehicles. Race regulations typically dictate a minimum distance behind the cyclist which the car must maintain and a minimum gap that must exist between two cyclists before the car may enter that gap. Individual time trials are often used as stages in stage races such as the Grand Tours ; these vary from short prologue time trials over no more than eight kilometres (designed to create an attacking racing style earlier in

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2046-477: A way that made the tandem impossible, in order to return to pack racing. In 2014, bump drafting was banned by NASCAR in the Nationwide Series and Camping World Truck Series . Tandem drafting made a return when NASCAR removed the restrictor plate and replaced them with tapered spacers, and with the flat noses and bumpers of the modern Gen 6 cars, drivers could more easily tandem and gain speed, much like

2139-430: 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

2232-472: Is a possibility of the engine overheating. Most motor sport aerodynamic analysis is performed using wind tunnel testing. This becomes difficult for drafting cases, if only because a very large wind tunnel is needed. CFD, a kind of virtual wind tunnel, is used by race teams to understand the car's performance while drafting. Racing games , such as most in the Mario Kart series, simulate drafting by giving

2325-497: Is also an Olympic event in which professionals are allowed to participate. Many of the top stage racers have also been top performers in the individual time trial, such as Lance Armstrong , Eddy Merckx , Alfredo Binda , Jacques Anquetil , Bernard Hinault , Fausto Coppi , Laurent Fignon , Greg LeMond , Miguel Indurain , Jan Ullrich , Ivan Basso , Alberto Contador , Cadel Evans , Fabian Cancellara , Tom Dumoulin , Bradley Wiggins and Chris Froome . Most recent winners of

2418-423: Is also different for time trialing. One-piece skinsuits that do not flap in the wind are common; tight lycra shoe covers help improve airflow over buckles and straps; long pointed helmets channel air down the riders back (the position of the helmet above the rider's back is crucial, it must be as close to the body as possible; too high and the air will just flow underneath the helmet. This is often hard to achieve as

2511-420: 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

2604-428: Is little time to react. Platooning is under study as a means to get the benefit while also increasing safety. Computer simulation ( computational fluid dynamics or CFD) is increasingly being used to analyse drafting. It is important to understand the aerodynamic behaviour of a motor vehicle when drafting, for example if the rear car is too close to the front car, the air supply to its radiator will be reduced and there

2697-604: 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

2790-427: Is occasionally used even in cross-country skiing , downhill skateboarding , and running . Some forms of triathlon allow drafting. Drafting occurs in swimming as well: both in open-water races (occurring in natural bodies of water) and in traditional races in competition pools . In a competition pool a swimmer may hug the lane line that separates them from the swimmer they are abaft of thereby taking advantage of

2883-435: Is often cited as a main reason for a decrease in the amount of overtakes. Drafting is most important at NASCAR's restrictor plate tracks, Talladega Superspeedway , Daytona International Speedway , and Atlanta Motor Speedway where the plates mean that much less power is available to push the large bodies through the air. Race cars reach their highest speeds on these superspeedways, so the aerodynamic forces are highest and

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2976-472: Is prevalent, and penalized drivers who are too rough in bump drafting. The 2010 NASCAR season allowed drivers more freedom; bump drafting was allowed anywhere, including turns. Kyle Busch is largely responsible for a different type of bump drafting, which is now referred to as "two-car drafting" and "tandem drafting". At a 2007 test session in Talladega, he asked Ryan Newman to push him from behind, and

3069-559: 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

3162-450: The Tour de France have been good time-trialists; exceptions include Marco Pantani , Carlos Sastre , and Andy Schleck , who were climbing specialists . To do well in an ITT, cyclists must Beginners are often criticized for putting in a J profile effort, meaning that they often go out too hard in the beginning, compensate by reducing their efforts in the middle, and then realize towards

3255-444: The crankset (chainset) to the bicycle and allows the crankset to rotate freely. It contains a spindle to which the crankset attaches, and the bearings that allow the spindle and crankset to rotate. The chainrings and pedals attach to the cranks. Bottom bracket bearings fit inside the bottom bracket shell , which connects the seat tube , down tube and chain stays as part of the bicycle frame . The term "bracket" refers to

3348-401: The "slingshot pass" is the most dramatic and widely noted maneuver associated with drafting. A trailing car (perhaps pushed by a line of drafting cars) uses the lead car's wake to pull up with maximum momentum at the end of a straightaway, enters a turn high, and turns down across the lead car's wake. The combination of running downhill and running across the zone of lowest aerodynamic drag allows

3441-410: 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 the different use of terminology by

3534-495: 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

3627-448: The UK the front wheel must have a minimum of 45% open area when viewed from the side, for safety reasons. UCI events still permit the use of disc wheels for the front, but it is very unusual. Many components are modified for aerodynamic efficiency, and manufacturers are now developing more integrated systems, such as brakes built into the fork or frame so as not to disturb the airflow. Clothing

3720-506: The aerodynamics expert Robby Ketchell at the University of New Hampshire to experiment with and select a formation of pacemakers that would best minimize drag on the professionals it sponsored in the project it termed Breaking2 . A Wired magazine report that interviewed various experts affiliated and unaffiliated with Nike found they universally expected more coordinated pacing efforts to occur in running after Breaking2, with two of

3813-412: 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

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3906-421: 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

3999-468: 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

4092-560: 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

4185-400: The defined parameters and must adapt their positions to fit the rules. Equipment used is very specialized, and component manufacturers can spend vast sums of time and money on wind tunnel testing to ensure their product is faster than the competition's. Deep section or solid disc wheels are often used to reduce turbulence around the spokes, but these can affect handling in windy conditions. In

4278-429: 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

4371-407: 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

4464-599: The early 2010s. After Ryan Newman's scary crash in the 2020 Daytona 500 , NASCAR made efforts to change drafting at superspeedways, where less horsepower was used: the removal of aero ducts to eliminate tandem drafting and decrease closing rates, and a smaller throttle body to lower the amount of air into a racecar. Some drivers have been known to draft behind other vehicles, particularly tailgating larger vehicles, to save fuel. For example, hypermilers using this technique can achieve 75 mpg or more (a 10% increase in efficiency of certain hybrid vehicles). Some sources say that

4557-401: The effects of drafting are strongest. Since restrictor plates were first used as a safety device, their effect has changed the nature of drafting. Vehicles no longer have sufficient horsepower or throttle response to maintain their drafting speeds upon exiting the draft; they can pull out and squeeze ahead but lack the response to clear the car being passed. This negates the slingshot maneuver. As

4650-463: 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

4743-522: The end that they have not put out enough effort during the race. As a result, the time trial is often considered the most difficult part of any major competition for young cyclists. Special aerodynamic time trial bicycles , clothing, helmets, aerobars and other equipment are often used in ITT events. Generally, components are designed to be as aerodynamic as possible, as most of the rider's effort goes into overcoming aerodynamic drag. The rider's position makes

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4836-464: 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

4929-427: The faster speedways and superspeedways used by NASCAR and ARCA , two or more vehicles can race faster when lined up front-to-rear than a single car can race alone. The low-pressure wake behind a group's leading car reduces the aerodynamic resistance on the front of the trailing car, allowing the second car to pull closer. As the second car nears the first, it pushes high-pressure air forward so less fast-moving air hits

5022-402: The front bird will create up-wash circulations. The birds flying behind will receive lift force from these up-wash vortices. Thus other birds in the flock do not need to work as hard to achieve lift. Studies show that birds in a V formation place themselves roughly at the optimum distance predicted by simple aerodynamic theory. Bottom bracket The bottom bracket on a bicycle connects

5115-411: The greatest difference, and most use the now-standard tuck position, using tribars to allow the rider to position their arms inline with the wind and allow their back to sit as low and flat as possible, reducing frontal area and improving air flow around the body. TT bikes often have lower handlebars than normal road racing bikes to facilitate this. Also, the saddle is sometimes moved forwards relative to

5208-440: The handlebars and bottom bracket to allow the hips a more natural angle of motion, improving performance (for UCI -sanctioned events, the saddle must be a certain distance behind a vertical line drawn through the center of the bottom bracket). Up until the late 1980s, low-profile 'bullhorn' handlebars were used, and normal drop handlebars before them. Then in the late 1980s triathletes developed so-called tri-bars that allowed for

5301-533: The idea. His arms-under-the-torso tuck was revolutionary, helping him and others to break world records and win World Championships. The UCI banned it in 1994, but he came back with the 'Superman' position, an evolution of the traditional tri position, but with the arms fully stretched out in front. This was also banned, and there are now strict rules governing the dimensions of handlebars, which can make life difficult for taller riders who fall outside

5394-447: 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

5487-520: The lead car and bumps into the rear of it, pushing the lead car ahead, to maintain momentum . If done roughly or in the wrong position (e.g. close to the entry of the turn), this tactic can destabilize the handling of the lead car, sometimes causing a crash. Use of the tactic in this manner is known as slam drafting . Due to the danger, NASCAR has attempted to limit the bracing on bumpers on cars, disallowed bump drafting in turns, introduced "no bump zones" on certain portions of speedways where this practice

5580-434: The lead car's spoiler. The result is less drag for both cars, allowing faster speeds. Handling in corners is affected by balance changes caused by the draft: the leading car has normal front downforce but less rear downforce. The trailing car has less front downforce but normal rear downforce. A car with drafting partners both ahead and behind will lose downforce at both ends. Similar to the "Belgian tourniquet" in cycling,

5673-436: The lead position (which requires the most effort and energy consumption). It can also be competitive or tactical : one competitor will try to stay closely behind another, leaving the follower with more energy for a break-away push to the finish line. Drafting behind another runner can conserve energy when facing a headwind . Generally the effect is much less pronounced than in cycling due to lower speeds. Nike worked with

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5766-432: The liquid slipstream in the other swimmer's wake. Drafting also occurs in competitive longboarding . It is believed, but not yet conclusively proven, that thoroughbred racing horses draft each other, especially in longer races. In cycling , any time one bicyclist is riding behind another, energy is conserved, especially at higher speeds. In road bicycle racing , the main (largest) group of tightly packed cyclists in

5859-400: 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

5952-649: 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

6045-427: 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

6138-453: 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

6231-403: 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

6324-416: 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

6417-421: The most common tailgating does not save gasoline even at freeway speeds because one is likely to accelerate and brake so frequently that any aerodynamic savings are lost through the brakes. On the show MythBusters , drafting behind an 18-wheeler truck was tested and results showed that traveling 100 feet (30 m) behind the truck increased overall mpg efficiency by 11%. Traveling 10 feet (3.0 m) behind

6510-402: 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

6603-466: The player a speed boost. Animals have been observed to use true drafting behavior reminiscent of auto racing or cycling. Caribbean spiny lobsters for example are known to migrate in close single-file formation "lobster trains". Vortex surfing is a related phenomenon that is currently being investigated by the US Air Force to save fuel on long-distance flights. The idea is to fly aircraft in

6696-480: The quoted experts predicting that behavior like "cooperative drafting", or races that incentivize cycling-peloton-like behavior could improve running times. In single seater, open wheel racing series such as Formula One and the IndyCar Series , as well as to a lesser extent in sports car racing , a technique known as slipstreaming is used. Along a long straight a car following close behind another uses

6789-420: The race) to longer distance events over flat or rolling courses, to timed ascents of mountain roads (mountain time trial). In the 1989 edition of the Tour de France , eventual winner Greg LeMond made up a 50-second deficit to runner-up Laurent Fignon over 24.5 km during the individual time trial on the final stage to win the race by 8 seconds, the smallest margin ever. The Vuelta a España often features

6882-543: 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

6975-417: The rider moves his head due to the suffering endured during a hard race). Fastest Stage (including Prologues) Fastest Non-Prologue Stage (including Stages of up to 20 km) Fastest Stage (including only Stages of up to 20 km) Fastest Stage (including only Stages of up to 40 km) Fastest Stage of Tour de France Fastest Prologue Stage of Tour de France Fastest Prologue Stage of Vuelta

7068-445: 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

7161-400: 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

7254-448: The slipstream created by the lead car to close the gap between them, hoping to be able to overtake the leader under braking for the next corner, or if they have a straightline speed advantage, to pass on the straight. However it is very difficult for cars to follow each other close together in fast corners as the "dirty" ( turbulent ) air that comes off the lead car unbalances the trailing car as its aerodynamic devices provide less grip. On

7347-419: The slipstream) behind each other. Any help between riders is forbidden. The rider with the fastest time is declared the winner. Bicycle construction is limited by regulations covering dimensions and other features such as weight. UCI Regulations At the professional level, time trials (TTs) are frequently accompanied by motorcycles , some carrying video equipment or race officials, and riders may be followed by

7440-445: 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

7533-415: 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

7626-409: 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

7719-469: The trailing car to carry extra speed and pass on the inside of the leader. Drafting was discovered by stock car racers in the 1960 Daytona 500 , when Junior Johnson found that he could use drafting as a strategy that helped him overcome the fact that his Chevrolet could not keep up with other cars, allowing him to win the race. Like Johnson, other drivers found they picked up speed running closely behind other cars, and as they experimented, they found that

7812-427: The truck produced a 39% gain in efficiency. Additionally, on the same episode, MythBusters demonstrated that it can be very dangerous for the following car if one of the truck's tires (or their recaps ) delaminate , as the chunks of ejected rubber can be large enough to cause serious harm, even death, to a driver following too closely. Drafters also face the danger that, if the vehicle in front stops suddenly, there

7905-411: 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 a hub, or rotates, as in

7998-460: 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,

8091-543: The two-car draft dominated the 2011 Daytona 500 and Budweiser Shootout . This strategy had also been very prominent at Talladega. In 2011, two-car tandem drafting was used for the extent of the Aaron's 499 , with many drivers drafting their own teammates (e.g., Jimmie Johnson and Dale Earnhardt Jr. drafted together, as did Jeff Gordon and Mark Martin ). For the 2012 season, the Sprint Cup series cars were modified in

8184-449: The upward part of the wingtip vortex of a leading aircraft. In 2003, NASA said one of its F/A-18 test aircraft had a 29% fuel savings by flying in the wingtip vortex of a DC-8 . The DC-8/F-18 flight was an exploratory investigation of large aircraft vortex-induced performance benefits on a fighter-type aircraft. The aircraft flew at 25,000 feet with a separation of about 200 feet nose-to-tail. The F/A-18 slowly moved in laterally to explore

8277-416: 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

8370-403: The vortex effects, NASA said at the time. The Air Force has also tested vortex surfing with C-17s using auto pilot in 2012, and indicated a 10% fuel saving. Tests in 2013 produced even greater fuel savings. Cooperative fluid dynamics techniques like drafting are also found in nature. Flocks of geese and some other birds fly in a V formation because the wingtip vortices generated by

8463-409: 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

8556-487: Was stunned to realize he was two seconds faster with Newman's help. At the newly paved Daytona International Speedway in 2011, Busch was the first to realize that the corners were smooth enough to allow a two-car draft for the complete length of the track. During test sessions on the track, when Busch was pushed by his brother Kurt 's Penske Racing teammate Brad Keselowski , they ran 15 mph faster than single cars. Other drivers quickly picked up on Busch's strategy, and

8649-473: 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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