<VV> Steering

[Alan and Clare Wesson]

Wrote this for another group I am in, but I thought I would send it to VV because the Corvair had the potential to have the best steering in history, but they blew it by gearing it unnecessarily low. I would be interested to hear the comments of the group - particularly engineers and people who know about steering and suspension design.

These comments apply to European cars (in particular the 1955 car I have in mind is the Lancia Appia, but those figures are also typical of most smallish (1100cc) European sedans from that era, most of which have FANTASTIC steering in comparison with the modern rubbish), but if you change the figures and dates a lot of them apply to American cars as well.

Cheers

Alan

P.S. Sorry about the metric measurements. Like most Brits I use Imperial, but this was written for a metric group.


Steering is the single most important aspect of vehicle design (apart from the gear lever and the seat base it is your only point of contact with the vehicle). And the tyres, your interface with which it controls, are your only point of contact with the road.

And it is the issue where I can best illustrate my oft-repeated statement that new is not necessarily better (in fact in the case of steering new is definitely worse).

The three issues governing steering quality are weight, feel and gearing. The weight of the steering is influenced by three things: a) the weight of the vehicle; b) the width of the tyres; and c) whether the car has front-, rear- or four-wheel drive. A light vehicle with narrow tyres and rear-wheel drive will naturally have light steering. If you increase the weight of the vehicle, the width of the tyres or switch from rear wheel drive, those factors will result in an increase in weight at the steering wheel rim.

The way that the weight of the steering at the wheel rim can be controlled (i.e. reduced) is by making it more low-geared (i.e. increasing the number of turns from lock to lock). The ideal is 2 - 2.5, because that means you almost never have to 'shuffle' your hands round the rim, and can turn the wheel very fast in an emergency situation. In the 50s most cars had narrow tyres, rear-wheel drive and 2-3 turns from lock to lock, and the steering was fantastic - extremely 'nervous', and giving you a sense of intimate contact with what was happening under the tyres (which, if you think about it, is pretty important from the point of view of controlling the vehicle, as it is your only feedback of information about the road surface you are travelling on). So if you encounter a patch of ice, mud or oil, or the car begins to slip or slide for some reason (intentional or otherwise...), you are instantly aware of it and able to control it.

Here is a timeline explaining how those issues have been compromised by industry developments, and why the steering on cars circa 1955 really was better than it is now.

1955-65 - rear wheel drive, average weight about 750 kg, tyre width about 5 inches, gearing 2-3 turns. This was the golden age - it would be very hard to improve on this.

1965-75 - rear wheel drive, average weight about 850 kg, tyre width about 5.5. inches, gearing 3-3.5 turns. The slide from perfection is beginning, influenced at first by increasing weight and slightly wider tyres.

1975-85 - rear wheel drive, average weight about 800 kg, tyre width about 5.5 inches, gearing 3.5-4 turns. A bit worse than 10 years before but not much.

1985-95 - front wheel drive, average weight about 950 kg, tyre width about 6 inches, non-powered steering, gearing has to be quite a bit lower to compensate for the extra weight, FWD and tyre width. Mostly 4-4.5 turns lock to lock, which feels very low-geared when being driven, and means that if you lose grip on a slippery surface you are unlikely to be able to turn the wheel fast enough to 'catch' the car. Andrew's Clio is one of this generation, and although Renault are better at engineering steering than most, I surmise that it will be around 4 turns if you go out and twirl the wheel.

1995-2000 - front-wheel drive, average weight about a tonne, tyre width 6-6.5 inches, hydraulic power steering. Gearing can be improved because of the power steering, and so goes back to about 3 turns lock to lock (Alfa Romeos are 2, which is the best available). Satisfactory 'feel' because the hydraulics allow that, but not as 'nervous' as the non-powered steering of the 50s. As the power steering is one of the many factors adding to vehicle weight, the cars from this period are also less economical than the generation before.

2000-2009 - front-wheel drive, average weight about 1.25 tonnes (a Golf weighs about 1400 kg), tyre width about 7.5 inches, electric power steering, about 2-3 turns lock to lock, but no sensation of being actually connected to the wheels whatsoever.

Vehicle weights now so high that manufacturers are coming under heavy pressure from the environmental lobby and the EU to reduce them (and so reduce fuel consumption), and so are looking for ways to achieve this. One way is to replace the hydraulic power steering with electric. This reduces the drag on the engine (is it not belt driven) and also reduces weight, but offers nowhere near the quality of steering feel. The gearing can at least be kept satisfactorily high, so a typical 2009 vehicle has high-geared and extremely light steering which gives no sensation whatsoever of contact with the road.

So we have made our cars massively heavy (which makes them worse to drive and less economical) and then sought to alleviate this slightly by saving a few kg by fitting electric steering, which makes them even worse to drive but gives a minute improvement in fuel consumption.

And that, ladies and gentlemen, is why steering nowadays is considerably worse than 10, 40 or 50 years ago (but only a bit worse than 20 and 30 years ago). I am not making it up - it is an uncontroversial statement and easily demonstrated, and the reasons lie in the design priorities forced on the manufacturers. 

It is just that we have got those design priorities all wrong...

Cheers

Al