Joined: Aug 2017 Posts: 176 Threads: 11
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Location: Upton upon Seven
Car type: 1931 RN, 1933 RP
A separate handling problem.
My RN has stopped trying to kill me!
I was running with it’s Longstone tyres at the recommended (by Longstone) at 30lb.
100% concentration was required to keep on the road as it was so skittish.
Handling was improved if I had a heavy passenger.
I have now reduced the pressure to 25lb and the handling performance in a straight line (as well as around bends) is transformed. It is wonderful now!
Roly
1931 RN, 1933 APD
Joined: Jan 2019 Posts: 1,481 Threads: 17
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Location: Bala North Wales
Car type: 1933 RP Standard Saloon
I note, on re-reading this thread, that it originally started out as an inquiry as to the advisability of altering the caster angle to make the car more stable. Somewhere on 'U Tube' there is a video of comparative driving tests on several pre-war Austins including a 10, 12/4 and an18/6, which I now cannot find. The commentator remarks (as I recall) that all the cars had very little self-centering characteristics because the caster angle was not very great. All the cars seemed stable at speed however, which , in the case of the 18, was about 70.
When I bought my first Austin Seven in the late '60s, all the front suspension and steering was shot and it was all over the road like a frightened rabbit. Overhauling everything in sight behind the front wheels cured the problem.
During the late seventies and early eighties, I had a special, built mostly out of bits I had acquired during ownership of my first one. This ran on standard suspension with a Girling front axle. This car was tuned and was capable of 70mph in a straight line. During the build, all the shackle pins, and all the steering gear was completely overhauled and, running on 4.50X17 tyres at (as I recall, as the car was probably not more than 6 to 7 cwt. all up) about 22psi, the car behaved itself very well indeed.
I am aware (from my days with the special) the important effect that tyre pressures have on handing. I replaced the tyres on my car shortly after buying it with 3.50 x 19 Mitas's and run them at 26psi front and rear. This appears perfectly satisfactory for a half ton car.
All the cars that I have ever driven with solid beam front axles tend to bump steer to a greater or lesser extend. My Series 3 Landrover does, as well as the Seven but you soon get used to allowing the car to pick its way over the lumps and bumps with a relaxed grip on the steering wheel.
I am lucky with my present saloon, inasmuch as it is an 'un-got-at' car, but I recently began to have handing problems beyond 40mph. Once again, the front suspension is all good and tight. I have the correctly handed radius rods (yes, after reading the comments in this thread I did check) and the only thing that I could find amiss was that the nearside track rod end had play in it. As I commented earlier, correcting this has not only sharpened the steering response, but has cured the car's waywardness (such as it was) at speed.
The RP, with its perpendicular architecture and narrow track, is never going to handle as well as a more modern car but, on the standard setup in well maintained condition, it behaves itself very well.
The moral of the tale is: if you are having handing problems,especially on a standard car, make sure that all the suspension and steering joints are in good order and lubricated and that the correct bits have been fitted and correct any faults found before playing around with the steering geometry. I have discovered that even a small amount of play somewhere can have a profound effect on the car's behaviour.
Joined: Aug 2017 Posts: 2,748 Threads: 31
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Location: Auckland, NZ
re Roland Alcocks comments,
I can only guess exactly why stiff tyres cause wander. Curiously, high pressure sharpens handling of moderns; radials now run near 10 psi higher then when first on the scene.
I wonder how Sevens on modern very flexible single wall ply tyres compare with the thick multi cotton ply original tyres when new. These were run at lower pressure than currently but were still mighty stiff. Late Edwardian and early vintage cars ran with small section multi ply cotton tyres at very high pressure. Possibly there were not sufficent fast sealed roads for handling on them to be a consideration.
Wrong toe in can introduce instability. It takes very little to distort the track rod.
(in modern times tyres had/have a ply rating but it is no longer the actual number of plies)
Joined: Aug 2017 Posts: 862 Threads: 16
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Location: North Yorkshire
Another thought about steering. I think there is the temptation to adjust the steering box with the wheels in the straight ahead position to eliminate play at the steering wheel. Due to the age of the steering box and the way in which they wear, this will cause the steering to be stiff on either lock. This is why you sometimes see Sevens going along a perfectly straight road in a series of zig-zags, the driver gripping the steering wheel with white knuckles and sweating profusely!
Joined: Aug 2017 Posts: 848 Threads: 22
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Location: Near Cambridge, UK
Car type: 1928 tourer (mag type), short chassis Gould Ulster
I understand that the hour-glass steering box was introduced to allow adjustment of play in the box to be at a minimum in the straight ahead position, with play designed in as you moved to left and right extremes. As these boxes wear you need to be careful when adjusting to ensure that they operate freely thoughout the range.
Robert Leigh
Joined: Sep 2019 Posts: 20 Threads: 7
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Location: Dorking Surrey
Car type: 1931 Sports boat tail
22-10-2019, 05:03 PM
(This post was last modified: 22-10-2019, 05:07 PM by Gibbo.)
Hugh. I am methodical, the radius arms are in good nick and same length and has the same angle at axle end obviously handed. I am working on an idea that will not efect the original inasmuch I can revert. Taking my time but radius arms off and parts being made. Will keep in touch Gibbo John
Hi Reckles Rat. I am an engineer and I dont bugger about I aproach all and any problems with care and respect. gibbo John
