Quote:
Originally Posted by Eatoniashoprat
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Hi Mike, there is either an error in the text or they have automatically factored in a different constant. The equation that I use is:
WR{
wheel rate} = (SF{
spring frequency}/187.8)^2 x SW{
sprung weight}. You can check this out on the Eibach Spring site for convenience:
http://performance-suspension.eibach...sion_worksheet as an example - just rearrange the equation or alternatively plug in the figures. You will see that the Cycles Per Minute (or Hz) are 80+. Remember on the front Macpherson struts the spring rate = the wheel rate for all intents and purposes and I have not deducted the unsprung weight from the corner weight as this is negligible.
Quote:
Originally Posted by Eatoniashoprat
That's a great thread, I'd forgetten about it. It should almost be linked in the suspension sticky.
I think I might just go with some 100lb springs for the front, see how it works, and then upgrade to 944 TB when I actually find some. Just hopefully with 100lb up front and stock out back it doesn't do anything weird.
Humble how do the 200lbs/inch ride on the street? There are a bunch of sources telling me that 100lbs/inch would be about right for my car seeing mostly street and some track but you have a lighter car with double the spring rate. Could this be due to a different rating system? I'll probably go with the QA1's as you have but I don't want to order the 100lbs/inch QA1's and have them too soft.
Mike
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If the standard spring rate on the front is 70-80lb/in then conventional wisdom suggests a 30% increase in rate for fast road that comes out to 91-104lb/in so that the 100lb/in is about right but the final value very much depends on your corner weight with all the extras you are carrying. On the rear where you suggest retaining the standard torsion bar the spring frequency is 95CPM on Humble's corner weights that will be too close to the front CPM of around 93CPM - that will induce uncomfortable pitching for and aft as the two frequencies are too alike, there needs to be at least a 10% difference. Why not add some coilovers to the rear with some light springs to increase the wheel rate?. The damper top mount will have some load capacity for light springing and if you get stiffer springs you could always add a 5 bar KC brace.
Clive