18 replies to this topic

[LD_Framework]

great to hear this then. Sorry you all have hilo and adjustable cone in your minis?

[Ethel]

The rubber cones do look basic, but there's actually some sophisticated engineering in the design. The rubber isn't just compressed, like a coil spring. The trumpet stretches the outer circumference allowing the trumpet to go partially inside the cone, allowing more suspension travel where a steel coil would bind up. 

 

It's also why tired old cones can be harder to squeeze out of the subby tower than getting new ones in.

[Cooperman]

Technically the rubber cone springs are what is known as 'rising rate' springs. That means that the actual spring rate, which in old money is measured as lbs/inch of deformation. As the cone is deformed upwards, the initial load/inch increases steadily until there is a much higher rate at near maximum deflection.

On rougher roads there is a need for a low initial rate to give a smoother ride and those Mini Spares cones do achieve this. There are also some road-rally cones which achieve the same thing.

Old cones get hard and the initial spring rate increases which gives a harsh ride. Once new ones of the optimum spec are fitted the ride improves enormously.

Coil springs are bad because even if they are 'rising rate', the rate may well not suit the Mini which was designed for rubber cones or hydrolastic units. Thus they are either too stiff on initial rate, which is OK for racing on smooth tracks, or soft but will 'coil bind' at higher deflections over bumps and damage/break the suspension or sub-frame.

[Spider]

The rubber cones, along with an appropriate flange trumpet, I feel is wildly dismissed as something cheap and nasty. Nothing could be further from the facts, they in in my view, a work of genius. Not only does that combination of cone and trumpet give variable rate, it has a lot of self damping (shock absorber) qualities that no other spring has. This is why, despite have a very much heavier spring rate, the coil springs (be it springs or coil overs) give a 'wollowing' ride and lots of body roll - they have no self damping. Coil Springs also lack travel when fitted in place of the Cones.

 

This is a typical used genuine Cone

 

 

There's the 2 rates there, one taken while compressing, the other in rebound. There is also a time factor involved here and that doesn't come out in this graph.