Morris Minor Owners Club

Nnnooooooooooo, I say keep the lever arms !

Just joking - a well engineered double wishbone with good geometry where the outboard wheel doesn't go +ve camber on bump will be worth having I'm sure!

outboard wheel doesn't go +ve camber on bump

Thinking of this from basic geometry (I'm no suspension expert) but to achieve this you just need parrallel arms (or whishbones) at loaded condition where the top arm is shorter so when travelling towards the bump stop it will give progressivelly more -ve camber.
This would allow the outer wheel to stay better aligned to the road on hard cornering...
Am I missing something, as this method does not seem to be used much?

This suspension spring rate lark has got me confused. When I fitted my diesel I wanted some extra strength in the bounce up front. I did the whole conversion with out modifying the body or chassis in any way beyond easy conversion back to standard in future. So the bolt-on coil overs seemed the answer. I kept the standard torsion bar setup at the standard ride hight and added the coil over system in aswell.
Surely though if the torsion is 220lbs and the coils are 120lbs that makes 340lbs of bounce. But i'm wrong?

That's right Robins - ideal for increased frontal weight and/or for anyone wanting a 'stiffer' front end! I think the comments are perhaps rather aimed at the design limitations of the Kit in question.
Ray - yes - wishbones as you describe with the upper one shorter and positioned to move inwards as it arcs upwards! The trick is to have the lower wishbone as long as possible - so it's movements in an arc have as little horizontal movement as possible on the tyre tread contact patch - so the track (at road surface level) remains constant or nearly so. And of course the whole lot nicely restrained fore and aft - and the steering connected in a manner that minimises bump steer!
Roll Centre and Centre of Gravity need to be considered too of course - but now we are getting into racing suspension rather than just improving the handling of a road car.

WHS ^^^ Brilliant stuff.

Spring rate is spring rate - yes the torsion bars are not 'progressive' - each degree of twist will give the same poundage resistance. Progressive bars would give relatively more resistance the more they are twisted - I have no idea how that would be done. Lowered or not - the T bar has to twist excatly the same amount to counter the car's weight! Adding another spring is just that - so 200 + 100 (or whatever the figures are) = 300. ie It will now take 300 lbs to compress the suspension by 1 inch where before it took 200 lbs. This assumes the extra spring has been added at the kingpin - and is being compressed by one inch for each inch of suspension compression. If its' inboard' (as these certainly are) - and only being compressed by say 1/2" for each inch of suspension deflection - then effectively it's only going to add half it's force to the equation - so 50 lbs in this case. The damping will also only be 'half effective'.

Quoting spring poundages is meaningless, you need to work out the wheel rate, if the spring mount is located on the wishbone right near the lower trunnion, the wheel rate will be higher than if the lower spring mount is located half way along the arm. The angle of the shock also affects the wheel rate and the angle of the lower arm to the ground.
In the early nineties, I added coil over shocks to my fiat engined Minor, the torsion bars were no way near stiff enough even with telescopic shocks (you should not be relying on shocks to prop the car up, the springs should be doing the work with the shocks controling the suspension mass). I ended up using 400 lb/inch springs with torsion bars with the coils springs giving an additional wheel rate of around 320 lb/inch (added to the torsion bar rate). Admitedly this was for track use, but handled brilliantly on the road and soaked the bumps up provided the shocks were not set too stiffly. It really is a case of tailoring the suspension to your driving requirements.
Don't think it is just the Minor which has suspension issues, I have been helping a friend who has a Westfield Megabusa to sort his suspension, and what an abortion Westfield made of the suspension geometry, it really is awful!! We are now getting it to handle properly after many months of work!

Suspension is easy to modify, time consuming to get right.

Martin