Another suspension topic - The deal with droop
05-27-2014, 07:33 PM
Post: #1
Another suspension topic - The deal with droop
Right, I’ve been doing a little bit of research surrounding the optimisation of coilover suspension for the road. For the last few years I’ve been running Driftworks CS2 Coilovers, which for those who don’t know have a bespoke spring set of 8kg/6kg and 16 way adjustment in all dampers. I’ve always liked the setup for its stability and level of adjustment in the dampers, but one thing I’ve never toyed around with is spring preload for droop adjustment.

In recent times, my car has gone back to becoming a daily driver, so it sees more country road action, which for the UK means some very bumpy and pothole covered bits of tarmac that can spell trouble for a lowered car with stiff springs. Due to the discomfort I get from hitting the smallest bumps and potholes even with the dampers on the softest setting, I looked to see if there was anything that could be done to make this a little more bearable.

The first thing I considered was looking into softer springs (6kg/4kg seems to be the preference to many here, so it was my first thought), but upon looking around, a lot of people say it wouldn’t make a noticeable enough difference. Also, after questioning Kam at Driftworks, his response was to sell my CS2s and get a whole other setup to eliminate my issue, as everything about the CS2s is bespoke and works together.

The next thing I looked into was adjusting the droop. There doesn’t seem to be a lot of technical information surrounding this that gave me the information I was after, with the exception of some information on the MX5 forums and on the Driftworks forums, which implied that this could improve the “harshness” of the ride as the shock absorber would not be “topping out”, which is why I’ve come here for more in-depth information.

Out of the box, the manual with the CS2s suggest that the preload on the springs should be set to 0 with just enough ability to move the spring inside its casing with your hands. Now, thinking about this in my head (I tend to work better with diagrams), I could imagine that, should one wheel fall into a pothole, the immediate effect encountered by the wheel hitting the further edge of the potholes on the way up would cause the damper to reach its full extent sooner and more rapidly due to the spring load pushing the damper up as the wheel compresses the spring and damper.

Now, thinking about it differently, if the spring had a negative preload (droop) of say 20mm (leaving a gap of 20mm at the top of the spring when the wheel is at full downward travel), when the same thing happens at the end of that previously mentioned pothole, the wheel would move up 20mm before engaging the spring, which would then in turn push up on the damper allowing an extra 20mm before the damper reaches its fullest extent, meaning you wouldn’t effectively feel the damper “topping out”, or if you did, it would be somewhat softened by the springs compression before it reaches that point.

What I’ve taken away from this is, you’re basically getting the effect of a progressive spring without actually having a progressive spring. The only downfalls being, you will reduce the amount of bump travel (which would be minimal considering the stiffness of the spring, that the negative preload isn’t wound off too far and if the dampers are adjusted accordingly) and you would be having a loose spring at full travel/droop, which is an MOT failure. My next step, should anyone advise this as the best route to take, is look at getting customised helper springs to help with this, as it means that the spring will still be held captive at full travel/droop.

I’m still trying to make logic of this setup and I haven’t ruled out the idea of going back to a standard lowering spring and shock setup, but I think that would defeat the object and it would be nice to try and get more from what I have. Could anybody confirm my thought process or provide any input to help me with my thinking?

Thanks in advance as always.
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Another suspension topic - The deal with droop - Jezza_hr - 05-27-2014 07:33 PM

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