Inboard brake
Encyclopedia
An inboard braking system is an automobile
technology wherein the disk brakes are mounted on the chassis of the vehicle, rather than directly on the wheel hubs. The advantage is a reduction in the unsprung weight
of the wheel hubs, as this no longer includes the brake disks and calipers.
Inboard brakes are fitted to a driven axle of the car, as they require a drive shaft to link the wheel to the brake. Most have thus been used for rear-wheel drive cars, although four-wheel drive and some front-wheel drives have also used them. A rare few rear wheel drive racing cars have also used inboard front disks, accepting the need to provide a drive shaft just to gain the unsprung weight advantage.
Inboard brakes for early racing cars have rarely used drum brake
s, although nearly all inboard brakes date from the disk brake era.
Excepting the case of vehicles with beam axles and vehicles having no suspension, in practice it is normal for inboard brakes to be mounted rigidly with respect to the body of the vehicle, often to the differential casing. This is done to move the weight of the braking mechanism from being carried by the wheels directly (unsprung weight
), to being carried indirectly by the wheels via the suspension (sprung mass). This then necessitates a means of transferring braking torque from the brake mechanism to the wheel, which is capable of operating despite the relative movement between body and wheel. Driven wheels already have shafting (or in older vehicles chains) which serve this purpose so there is no penalty for them, but undriven wheels require a similar mechanism which is then called a brake shaft.
The benefit of such a system is primarily the reduction of unsprung weight which improves handling
and ride
. The suspension does not have to resist twisting when the brakes are applied. The wheels don't enclose the brake mechanism allowing greater flexibility in wheel offset
, and placement of suspension members. It is also much easier to protect the brake mechanism from the outside environment, and protect it from water, dust, and oil. Of secondary importance is flexible brake pipes are avoided and rigid pipes allow increases in brake fluid pressure, allowing a smaller disks for a given braking torque.
The mechanical disadvantages are largely those of added complexity. Undriven wheels require a brake shaft. It is more difficult to arrange for cooling air to flow over the wheel, and air ducting can be required, to prevent brake fade.
There can be practical difficulties,in servicing the brake mechanism. Instead of simply removing a wheel to renew pads and discs, the vehicle may need to be jacked up, so a mechanic can work underneath the vehicle. Additionally renewing brake discs can require dismantling the half axle. This greatly discourages their use in motorsport, and the additional time makes for greater labour cost when servicing these parts.
This system was more common in the 1960s, found on such cars as the Jaguar E-Type
and Citroën 2CV
. The Hummer H1
is one of the few modern vehicles fitted with inboard brakes, to accommodate each wheel's portal gear
system.
Hybrid gasoline/electric vehicles may be considered to have partial inboard braking, because the devices used for the regenerative part of the braking are usually mounted inboard.
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...
technology wherein the disk brakes are mounted on the chassis of the vehicle, rather than directly on the wheel hubs. The advantage is a reduction in the unsprung weight
Unsprung weight
In a ground vehicle with a suspension, the unsprung weight is the mass of the suspension, wheels or tracks , and other components directly connected to them, rather than supported by the suspension...
of the wheel hubs, as this no longer includes the brake disks and calipers.
Inboard brakes are fitted to a driven axle of the car, as they require a drive shaft to link the wheel to the brake. Most have thus been used for rear-wheel drive cars, although four-wheel drive and some front-wheel drives have also used them. A rare few rear wheel drive racing cars have also used inboard front disks, accepting the need to provide a drive shaft just to gain the unsprung weight advantage.
Inboard brakes for early racing cars have rarely used drum brake
Drum brake
A drum brake is a brake in which the friction is caused by a set of shoes or pads that press against a rotating drum-shaped part called a brake drum....
s, although nearly all inboard brakes date from the disk brake era.
Excepting the case of vehicles with beam axles and vehicles having no suspension, in practice it is normal for inboard brakes to be mounted rigidly with respect to the body of the vehicle, often to the differential casing. This is done to move the weight of the braking mechanism from being carried by the wheels directly (unsprung weight
Unsprung weight
In a ground vehicle with a suspension, the unsprung weight is the mass of the suspension, wheels or tracks , and other components directly connected to them, rather than supported by the suspension...
), to being carried indirectly by the wheels via the suspension (sprung mass). This then necessitates a means of transferring braking torque from the brake mechanism to the wheel, which is capable of operating despite the relative movement between body and wheel. Driven wheels already have shafting (or in older vehicles chains) which serve this purpose so there is no penalty for them, but undriven wheels require a similar mechanism which is then called a brake shaft.
The benefit of such a system is primarily the reduction of unsprung weight which improves handling
Car handling
Automobile handling and vehicle handling are descriptions of the way wheeled vehicles perform transverse to their direction of motion, particularly during cornering and swerving. It also includes their stability when moving at rest. Handling and braking are the major components of a vehicle's...
and ride
Ride quality
Ride quality refers to the degree of protection offered vehicle occupants from uneven elements in the road surface, or the terrain if driving off-road. A car with very good ride quality is also a comfortable car to ride in. Cars which disturb vehicle occupants with major or minor road...
. The suspension does not have to resist twisting when the brakes are applied. The wheels don't enclose the brake mechanism allowing greater flexibility in wheel offset
Offset (wheel)
The offset of a vehicle's wheel is the distance between the centerline of the wheel and the plane of the hub-mounting surface of the wheel. It can thus be either positive or negative, and is typically measured in millimeters...
, and placement of suspension members. It is also much easier to protect the brake mechanism from the outside environment, and protect it from water, dust, and oil. Of secondary importance is flexible brake pipes are avoided and rigid pipes allow increases in brake fluid pressure, allowing a smaller disks for a given braking torque.
The mechanical disadvantages are largely those of added complexity. Undriven wheels require a brake shaft. It is more difficult to arrange for cooling air to flow over the wheel, and air ducting can be required, to prevent brake fade.
There can be practical difficulties,in servicing the brake mechanism. Instead of simply removing a wheel to renew pads and discs, the vehicle may need to be jacked up, so a mechanic can work underneath the vehicle. Additionally renewing brake discs can require dismantling the half axle. This greatly discourages their use in motorsport, and the additional time makes for greater labour cost when servicing these parts.
This system was more common in the 1960s, found on such cars as the Jaguar E-Type
Jaguar E-type
The Jaguar E-Type or XK-E is a British automobile, manufactured by Jaguar between 1961 and 1975. Its combination of good looks, high performance, and competitive pricing established the marque as an icon of 1960s motoring...
and Citroën 2CV
Citroën 2CV
The Citroën 2CV |tax horsepower]]”) was an economy car produced by the French automaker Citroën between 1948 and 1990. It was technologically advanced and innovative, but with uncompromisingly utilitarian unconventional looks, and deceptively simple Bauhaus inspired bodywork, that belied the sheer...
. The Hummer H1
Hummer H1
The Hummer H1 is a civilian off-road vehicle based on the M998 Humvee, which was created by AM General. The vehicle was produced from 1992 through 2006, and was the first of what became the Hummer line...
is one of the few modern vehicles fitted with inboard brakes, to accommodate each wheel's portal gear
Portal gear
Portal axles are an offroad technology where the axle tube is above the center of the wheel hub.-Description:Compared to normal layout, portal axles enables the vehicle to gain a higher ground clearance, as both the axle tube and differential casing are tucked up higher under the vehicle.Due to...
system.
Hybrid gasoline/electric vehicles may be considered to have partial inboard braking, because the devices used for the regenerative part of the braking are usually mounted inboard.
Cars with inboard brakes
- Alfa Romeo AlfasudAlfa Romeo AlfasudThe Alfa Romeo Alfasud is a compact car made by Alfa Romeo of Italy from 1971 to 1989. It was considered one of Alfa Romeo's most successful models, sold 893,719 examples from 1972 to 1983 plus 121,434 Sprint versions from 1976 to 1989. A common nickname for the car is ’Sud...
, an unusual example where the front wheels have inboard disks. - AlfettaAlfa Romeo AlfettaAlfa Romeo GTV redirects here. For 916 series GTV see Alfa Romeo GTV & SpiderThe Alfa Romeo Alfetta is an Italian rear-wheel drive executive saloon car and fastback coupé produced from 1972 until 1987 by Alfa Romeo...
, GTV, GTV6, GiuliettaGiuliettaGiulietta may refer to:*Giulietta Masina – Italian actress.*Alfa Romeo Giulietta – Alfa Romeo's various anniversary cars.-See also:*Romeo and Juliet *Juliette *Juliet...
, 75 / MilanoAlfa Romeo 75The Alfa Romeo 75, sold in North America as the Milano, was a compact sports saloon / compact executive car produced by the Italian automaker Alfa Romeo between 1985 and 1992...
, 90Alfa Romeo 90The Alfa Romeo 90 is an executive car produced by the Italian automaker Alfa Romeo between 1984 and 1987.Designed by Bertone and introduced at the 1984 Turin Motor Show, the 90 was pitched between the Alfa Romeo Alfetta and the Alfa Romeo Alfa 6, both of which were soon discontinued after the 90's...
, SZAlfa Romeo SZThe Alfa Romeo SZ or ES-30 is a high-performance limited-production sports car/road-concept car built between 1989 and 1991 with partnership via Centro Stile Zagato, Centro Stile Alfa Romeo and Centro Stile Fiat... - Audi 100 LS
- British Racing MotorsBritish Racing MotorsBritish Racing Motors was a British Formula One motor racing team. Founded in 1945, it raced from 1950 to 1977, competing in 197 Grands Prix and winning 17. In 1962, BRM won the Constructors' Title. At the same time, its driver, Graham Hill became World Champion...
: Some BRM racing cars had a single inboard disk brake, acting on both back wheels. - Citroën 2CVCitroën 2CVThe Citroën 2CV |tax horsepower]]”) was an economy car produced by the French automaker Citroën between 1948 and 1990. It was technologically advanced and innovative, but with uncompromisingly utilitarian unconventional looks, and deceptively simple Bauhaus inspired bodywork, that belied the sheer...
, DSCitroën DSThe Citroën DS is an executive car produced by the French manufacturer Citroën between 1955 and 1975. Styled by Italian sculptor and industrial designer Flaminio Bertoni and the French aeronautical engineer André Lefèbvre, the DS was known for its aerodynamic futuristic body design and innovative...
, GSCitroën GSThe Citroën GS and Citroën GSA are small family cars produced by the French automaker Citroën. The GS was voted European Car of the Year for 1971, and was probably the most technologically advanced car in its class when launched, with class leading comfort, safety and aerodynamics.-Market...
, SMCitroën SMThe Citroën SM is a high-performance coupé produced by the French manufacturer Citroën from 1970 to 1975. The SM placed third in the 1971 European Car of the Year contest, trailing its stablemate Citroën GS, and won the 1972 Motor Trend Car of the Year award in the U.S. in 1972.-History:In 1961,...
, AmiCitroën AmiThe Citroën Ami is a supermini produced by the French automaker Citroën from 1961 to 1978. The Ami and stablemate Citroën Dyane were replaced by the Citroën Visa and Citroën Axel . The Ami was for some years the best-selling car model in France...
, DyaneCitroën DyaneThe Citroën Dyane is an economy car/supermini produced by the French automaker Citroën from 1967 to 1983. Based on the Citroën 2CV, 1,444,583 examples were manufactured...
, AxelCitroën AxelThe Citroën Axel was a supermini automobile produced between 1984 and 1990 and developed in co-operation by Citroën of France and Automobile Craiova, a joint venture company with the Romanian government....
and other CitroënCitroënCitroën is a major French automobile manufacturer, part of the PSA Peugeot Citroën group.Founded in 1919 by French industrialist André-Gustave Citroën , Citroën was the first mass-production car company outside the USA and pioneered the modern concept of creating a sales and services network that...
models - DKW JuniorDKW JuniorThe DKW Junior was a small front wheel drive saloon manufactured by Auto Union AG. The car received a positive reaction when first exhibited, initially badged as the DKW 600, at the Frankfurt Motor Show in March 1957...
plus other models - Hummer H1Hummer H1The Hummer H1 is a civilian off-road vehicle based on the M998 Humvee, which was created by AM General. The vehicle was produced from 1992 through 2006, and was the first of what became the Hummer line...
- Jaguar E-TypeJaguar E-typeThe Jaguar E-Type or XK-E is a British automobile, manufactured by Jaguar between 1961 and 1975. Its combination of good looks, high performance, and competitive pricing established the marque as an icon of 1960s motoring...
, Jaguar XJJaguar XJJaguar XJ is the designation that has been used for a series of luxury saloon cars sold under the British Jaguar marque. The first XJ was launched in 1968 and the designation has been used for successive Jaguar flagship models since then. The original model was the last Jaguar saloon to have had...
(until XJ40), Jaguar XJ-S - Lancia AureliaLancia AureliaThe Lancia Aurelia is a car that was produced by the Italian manufacturer Lancia. Designed by Vittorio Jano, the Aurelia was launched in 1950 and production lasted until the summer of 1958....
- Lotus Twelve racing car, and most other racing Lotuses after.
- Lotus EliteLotus EliteNot to be confused with the Lotus Elise.The Lotus Elite name was used for two vehicles from Lotus Cars.-1957:The first Elite or Lotus Type 14 was an ultra-light two-seater coupé, produced from 1958 to 1963....
, ElanLotus ElanLotus Elan is the name of two convertible cars and one fixed head coupé produced by Lotus Cars. The original Type 26, 26R Racing version , 36R Racing version , 36 Fixed Head Coupe, 45 Drop Head Coupe, and the "Type 50" +2 Coupe, circa 1962 to 1975, are commonly known as the '60s Elans...
and Esprit - Mercedes-Benz W196Mercedes-Benz W196The Mercedes-Benz W196 was the Mercedes-Benz Formula One entry in the and Formula One seasons, winning 9 of 12 races entered in the hands of Juan Manuel Fangio and Stirling Moss....
and 300SLRMercedes-Benz 300 SLRThe Mercedes-Benz 300 SLR was a sportscar racing car for the 1955 World Sportscar Championship season, which it won.-Technical highlights:... - Monteverdi Hai 450 SS
- Oldsmobile ToronadoOldsmobile ToronadoThe original Toronado began as a design painting by Oldsmobile stylist David North in 1962. His design, dubbed the "Flame Red Car," was for a compact sports/personal car never intended for production...
- OltcitOltcitThe Oltcit was a Romanian car developed in co-operation with Citroën of France in the 1980s. It is a small three-door hatchback, based on the Citroën Prototype Y and built in Craiova at the Automobile Craiova plant.-History:...
- Rover P6Rover P6The first P6 used a 2.0 L engine designed specifically for the P6. Although it was announced towards the end of 1963, the car had been in "pilot production" since the beginning of the year, therefore deliveries were able to begin immediately. Original output was in the order of . At the...
- Subaru GSubaru GThe Subaru FF-1 G was a compact car from the 1970s, replacing the FF-1 Star. It was a front wheel drive vehicle with a typical Subaru EA61 or EA62 flat-4 engine. A fully independent torsion bar suspension and rack and pinion steering were impressive for the time. The inboard front drum brakes...