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| Re: Gemini coils in CA18 1200.... Where to cut? |
Subject: Re: Gemini coils in CA18 1200.... Where to cut?
by dattodude on 2008/1/2 10:48:29
A spring is a complex bit of technology. You need it to sit at a certain height. And for the street, that involves a little compression of the spring from it's free length. The maximum corner weight then needs to be calculated in terms of static corner weight 'traded off against' the dynamic corner weight estimated during a 1G->2G hard turn on a race track.
For race, you'd set it up for the dynamic corner weight, for the street you'd be looking more closely at the using the static corner weight and suspension travel.
The length of the shock travel completely determines the spring rate. If you shorten a 180B strut (like I have) I now have to arrest the car from bottoming out 2 inches quicker.
If I have 5 inches to arrest 500pds of corner weight, then using 110 pound/inch springs is fine. After 4.54 inches the springs will support the weight.
If I've changed the suspension travel to 3 inches, I'd want to be supporting the weight after in 2.5 inches, that would need 200 pound springs.
So by removing 1/2 the travel (or bump), I'm required to double the spring weight.
These are totally hypothetical, and I'd recommend 250 pound/inch springs at 225mm free length for a 1200 with shortened/recupped 180b struts.
These numbers are for the weight being supported by the spring, the angle of the strut and it's relation to the vertical force (gravity) is what I'm talking about. It's not necessarily just the corner weight.
Totally off the topic of what to do with your gemini springs.. just thought you'd like to have a think about the things that have kept me awake during my 1200 rebuild, with both custom front and rear suspension. Tuning my suspension has been expensive and time consuming. But I'm finally getting happy with it all.
Most of this stuff was learned by me reading a few 'racing suspension' books, and reading Ferrol Errols website (datrats.com.au), thanks Errol. Errol's website no longer has the information I learnt from, but I wisely took a copy, if anyone wishes to read the same.
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