Hydrosteer was the name given by Hydrosteer Limited of Luton, England, (later Cam Gears Ltd) to its automotive power steering system of the 1960s and early 1970s. Based on a cam and peg system, it was characterised by its fully integrated design and variable steering ratio. Introduced in 1960, it was fitted to several, mainly British, luxury automobiles of the era. Frequently described by road testers as too light and lacking in road feel, it was largely supplanted by other systems in the 1970s, notably the Marles Varamatic.
The 1960s Hydrosteer system should not be confused with Hydrosteer Pty Ltd, an Australian company established in 1981 as a provider of heavy truck steering technology in that country.
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The Hydrosteer power steering system was fitted to the following vehicles:
Facel Vega II (optional)
Humber Super Snipe Series V (optional)
Humber Imperial
Rover P5 3-Litre Mark 1a (optional)
Rover P5 3-Litre Mark 2 Saloon and Coupe
Rover P5 3-Litre Mark 3 Saloon and Coupe
Rover P5B 3.5-Litre Saloon and Coupe
Vanden Plas Princess 4-Litre
Wolseley 6/110 (optional)
[1] The Hydrosteer system was based on a conventional cam-and-peg mechanism, except that the cam is surrounded by the skirt of a piston within the body of the steering box. Hydraulic power from the power steering pump is transmitted directly from the piston to the peg carrier. A spool type hydraulic valve moves along the axis of the cam in response to steering wheel movement, causing oil pressure to be applied to one side or other of the piston according to the direction the steering wheel is turned.
Tha cam track is not a regular helix but varies in pitch angle and depth. The variation in steering ratio between straight ahead and full lock results from the variance in pitch angle of the track. The more the steering wheel is turned, the lower the steering ratio becomes. In the Rover P5B, for example, [2] the ratio of the power steering unit was 16:1 at the straight ahead and 11.3:1 at full lock.
The effect of the variable ratio is to give very light and relaxed steering at the straight ahead, with increased reaction when cornering. The system was designed to be fail-safe, so that the driver should still be able to steer in the event of a failure of the power system.
The major benefit of the Hydrosteer system is reduction in the amount of steering effort required of the driver, particularly at low road speeds or when a lot of turning is involved. Also, the Hydrosteer system was fully integrated into the steering box with no external jacks, giving it an advantage over earlier systems with external jacks, which needed more space and were heavier.
Whilst advanced for its time, the Hydrosteer system did have certain drawbacks, in common with all variable ratio steering systems. It was more complicated and expensive than a constant ratio power assisted system. It could also catch drivers out when they attempted to correct for understeer or oversteer, the non-linear response of the steering working against the driver in such circumstances.
The Hydrosteer system was also criticised for feeling far too light under most circumstances. A particularly scathing article appeared in Car magazine in January 1968[3] stating “Not even an octagenarian with Parkinson’s disease could possibly run such a risk [of losing control of the car due to sneezing] with the rival Rover [Hydrosteer] system, which is also progressive but with a complete absence of feel. This is power steering in the true American sense; we find it difficult to call to mind any virtues that anyone could claim for it apart from the obvious observation that parking would probably be impossible for a woman or an old man without some sort of assistance; on the other hand, we can think of every reason why it should be changed for something more sophisticated …”.
Indeed, use of the Hydrosteer system in cars effectively died out with the generation of 1960s models to which it was fitted. For example, the Rover P6B 3500S that followed the Rover P5B used the Marles Varamatic variable ratio system, which was slightly heavier in most circumstances and arguably had more road feel, although that system too failed to survive much beyond the 1970s.
![[2]](http://www.gracesguide.co.uk/images/8/82/Im19621003Mot-Hydrosteer.jpg){kind=link}