Talk Morgan Forums Morgan Sports Cars Morgan Plus Four, Supersport & Plus Six (CX & CXV Generation Vehicles) Plus 6 'skipping' on full lock

This is not a power steering 'feature' by any chance? I don't get this with my Trads.

I don't get it on my CX P4 nor did I get it with my 4 trads

Yep, I'm with CooperMan and Akermann's principle. Prior to motor vehicles coming into being they even used a simple variation of this theme on horse drawn wagons to aid tight turns but with driven wheels a differential was required to allow the inner rear wheel to have less rotation than the outer wheel even under a driving force(rear wheels only originally) when turning but then they found that more accuracy was required to let the steering wheels behave whilst traveling on different circumferences and not fight each other to acquire a different steering track ie. to drive on a parallel track whilst turning. There is a limit of range in which this can be achieved and at the extremes of steering lock it starts to go out of a compatible angle, coupled with the tyre profile and footprint of the inner wheel it becomes unable to track a suitable radius in both wheels and so in effect drags or skips on the inner wheel and I suspect this is what you are experiencing. The Morgan is light and so isn't damped by a heavy engine at these extremes of tyre drag and having a fairly long wheel base and narrow track coupled I imagine with perhaps a degree or so more steering lock than would restrict this happening so much: in order to achieve the best slow speed maneuverability I imagine, was seen as acceptable as after all you won't be using that amount of steering lock when driving normally which will then be well within Ackemanns steering criteria. Imagine the car being twice as long you would in fact have very little maneuverability, well if Morgan hadn't allowed the steering rack to produce a lock slightly beyond a perfect result then tight and slow maneuvering would present problems. How this is fully achieved requires more detail than I want to go into here and in trying to keep it simple I hope I haven't done the opposite. Martin.

Not had it on a 3.7 Trad with PAS

Hi, if it’s a metallic noise and not a caoutchouc noise I had this on my 2020 plus Six… it was the inner “corner” of the alu wheel that was touching the back of the bellow front suspension triangle.
It happen only with me because of my 120 kg 🥵
(Sorry for the approximative English)

Could this not be due to, or at least be exacerbated by the run flat tires with fiirm sidewalls? I also experienced this effect with other cars. I guess it is even worse when tires are cold.

Whilst Ackermann steering is a very easy to understand concept where the wheels turn to follow a radius with the same centre, as below, it only works at very low speeds. Tyre slip is the dynamic that spoils this otherwise ideal at higher speeds, so modern cars use a version by way of compromise.



Taken to the extreme of F1 some cars go as far as using anti-ackermann where the outside wheel turns in more than inner benefitting high speed cornering. Clearly though with a sports car on wide tyres the compromise will lead to tyre scrub on full lock at manoevering speeds.