Vehicle steering

In plain language

Steering is how a driver points a vehicle where it needs to go. In earlier designs the front wheels turned together on a pivoted axle, so they had to share a common arc in a corner. Georg Lankensperger's stub-axle arrangement, dated to 1815 or 1816 in the sources, let each front wheel turn on its own pivot, so the two wheels could follow the different arcs they trace in a turn.

Over time the steering wheel replaced the tiller, gears were added to make the wheel easier to turn, and power assistance followed to reduce the effort a driver needs. The geometry is named after Rudolph Ackermann, whose agent patented it in England in 1818 for horse-drawn carriages, although Georg Lankensperger of Munich is credited with inventing the arrangement.

Technical explanation

Ackermann steering geometry uses steering arms set at an angle so that the two front wheels turn about a common centre. In a turn the inner wheel turns more sharply than the outer one, so each wheel follows its own circle. The original parallel-arm version had a defect, which Jeantaud overcame. Motor Sport's 1954 article judges 'Ackermann-Jeantaud' the fairest description of the system then commonly used. Wikipedia notes that Erasmus Darwin may have a prior claim dating from 1758, but this profile does not rely on that claim.

Pure Ackermann geometry is a low-speed approximation. It ignores dynamic and compliant effects, so modern cars do not use it unmodified. Some racing cars use reverse Ackermann geometry at high speed to compensate for the large difference in slip angle between the inner and outer front tyres during cornering.

By the turn of the twentieth century, the standard gear comprised a steering wheel, column, worm reduction gear, cross-shaft, drop arm and Ackermann linkage. Motor Sport's 1954 history records that direct tillers on early Panhards were judged dangerous at useful speeds, that the worm reached a peak around 1914 before declining during cost-cutting, and that a rack-and-pinion steering gear appeared on Pecqueur's 1828 wagon. The article notes that rack-and-pinion gears were then rapidly coming into favour. Arthur E. Bishop's US patent 3,753,378 for a variable-ratio rack and pinion steering gear was published in 1973.

Power steering adds hydraulic or electric assistance to the linkage. Wikipedia reports that Francis W. Davis of Pierce-Arrow invented and demonstrated the first practical power steering system in 1926, and that General Motors later calculated his refined hydraulic design would be too expensive to produce. Chrysler introduced the first commercially available passenger-car power steering, called Hydraguide, on the 1951 Chrysler Imperial, and Cadillac followed in 1952. Electric power steering first appeared on a mass-produced passenger car on the Suzuki Cervo in 1988. In 2023 a Lexus model was introduced with a steer-by-wire system that eliminates the mechanical linkage between the steering wheel and the wheels.

What the evidence says

Each statement is typed by the strength of its evidence and linked to the source that supports it.

Limitations and open problems

• Historical attributions differ across sources. Lankensperger's invention is dated 1815 by one source and 1816 by another, and Erasmus Darwin may have a prior claim. Only one source gives a patent number for the 1818 patent (2 412), and the other sources do not confirm it, so this profile gives no number.
• Pure Ackermann geometry is a low-speed approximation that ignores tyre compliance and dynamic effects, so it does not describe steering at speed.
• Early claims of power steering, such as an 1876 installation credited to a man named Fitts, are poorly documented and are not included here.
• The sources reviewed do not agree on whether the 1951 Chrysler Hydraguide was standard or optional, and no verified price is given.
• Steer-by-wire removes the mechanical link to the road wheels, so its safety depends on electronic redundancy. The sources reviewed do not cover long-term reliability data for these systems.

Possible future uses

Timeline

1. 25 May 1816A Bavarian privilege dated 25 May 1816 is cited for Georg Lankensperger's steering invention in Munich. Sources: [3], [2]
2. 1818Rudolph Ackermann, described as Lankensperger's agent in England, patents the steering geometry that now bears his name. The patent covers horse-drawn carriages. Sources: [4], [1]
3. 1828Motor Sport's 1954 history records a rack-and-pinion steering gear on Pecqueur's 1828 wagon. Sources: [5]
4. 1926Francis W. Davis of Pierce-Arrow is reported to have invented and demonstrated the first practical power steering system. Sources: [6]
5. 1951Chrysler introduces Hydraguide, the first commercially available passenger-car power steering, on the 1951 Chrysler Imperial. Sources: [6]
6. 21 Aug 1973US patent 3,753,378 for a variable-ratio rack and pinion steering gear, by Arthur E. Bishop, is published. Sources: [7]

Glossary

Ackermann steering geometry

A linkage arrangement in which the front wheels turn about a common centre, so the inner wheel turns more sharply than the outer one.

Tiller

A straight lever fixed to the front axle or steering column, used to turn the front wheels before steering wheels became common.

Rack and pinion

A gear pair in which a toothed pinion on the steering shaft moves a straight toothed bar, the rack, to turn the wheels.

Slip angle

The angle between the direction a tyre is pointing and the direction it is actually travelling, which grows as cornering forces increase.

Sources

1. other
   Ackermann steering geometry
   Wikipedia (English), 21 Sept 2026. Accessed 22 Oct 2026.
2. other
   Georg Lankensperger
   Wikipedia (English), 30 Mar 2026. Accessed 22 Oct 2026.
3. other
   Lankensperger, Georg, in Neue Deutsche Biographie 13
   Hans Christoph Graf von Seherr-Thoß. Deutsche Biographie (Neue Deutsche Biographie, vol. 13, pp. 617 f.), 1982. Accessed 22 Oct 2026.
4. other
   Rudolph Ackermann
   Grace's Guide to British Industrial History, 1 Dec 2025. Accessed 22 Oct 2026.
5. other
   Historical Notes: Steering Gear
   Motor Sport magazine, Jan 1954. Accessed 22 Oct 2026.
6. other
   Power steering
   Wikipedia (English), 7 Nov 2025. Accessed 22 Oct 2026.
7. patent
   Rack and pinion variable ratio steering gear
   Arthur E. Bishop. Google Patents (record for US patent USRE28740E), 23 Mar 1976. Accessed 22 Oct 2026.

Revision history

3 changes since this profile was created.