Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Bumb steer and vertical angle of wheels

Like most decent wishbone front suspension systems, the Morgan is unequal lengths with the lower wishbone being longer than the upper one. This means as you deflect, the camber becomes more negative, and that is exactly what you want when cornering as you lean harder on a wheel that goes more negative camber. Counters tyre roll amongst other things.

But, for good design this also means the arc described by the steering arm must be such that there is no steering force with deflection. So if the steering system effectively forms a third wishbone fitting in with the other two, no bump steer results.

With a 'droopy' steering arm that is not parallel to either wishbone you will get pronounced bump steer as quite obvious to me at least, were you to jack the car, disconnect the spring (quite easy on a 5 speeder) you'd be free to move the wheel up and down.

On this car, looking at the right wheel, it would turn left as you raised the wheel, and right as you lowered it.


But on this one were you to do the same thing, it would stand a much better chance of having no wheel movement, so no bump steer.

I’ve just re-used the pictures that are already in this thread as they show the point perfectly.

Thanks with regards to the term "camber angle". I'm a stupid Dane, so I had no clue as to the English term. Also thank you very much for the rest of the explanations

Martyns explanation sounds logical, but do the factory designers not know this stuff? Maybe they actually designed bump steer in, to make the driving experience more 'interesting'?

And btw AQM, there is no need for self castigation or the explanation of 'stupid Dane'. If I could speak Danish only half as well as you speak English I would be very happy.

Thank you, Paul, much appreciated

Love the photos,

I think you need to do something about your horizontal alignement in the first photo and in the second it seems OK but I really think its about to go pear shaped again

Wow a 5 wheeler, I will stick to my three!

Minor correction to last night's post, the right hand wheel is of course actually the car's left wheel (car left and right is taken from sitting in the driving seat).

As for whether designers know this stuff, I'd hope so, one could not describe oneself as an automotive engineer otherwise. I'm not, I'm an electrical engineer!

That's the point I was making Martyn, auto designers do know all this basic stuff, so why is the 5 speeder so twitchy - it's almost as if they have made it so on purpose? Despite customers protestations, nothing has yet been done to remedy the situation either.

What about a mass demand to go back to the earlier front, or at least an explanation as to why they did it?

It can't be because of safety, there has to be another reason. I fear it's cost cutting too.

One would think they had already done the cost calculations, and figured they could make good money by introducing this, even in smalller quantitites. And now when they had to step up production because the market was bigger than they predicted, they make something worse because of costs?

I sure hope it's not cost related, because if so, they just got greedy.

It would be interesting to know if Morgan regard this as a problem and whether they feel it needs to be sorted or indeed if they are working on it.