Jersey Posted July 20, 2004 Share Posted July 20, 2004 Hey all. I installed a set of custom springs on my 240 a while back but don't know their rates. I'm going to be replacing my struts soon so i was wondering if there was anyway to check the rates while they're out? Thanks in advance. Quote Link to comment Share on other sites More sharing options...
johnc Posted July 20, 2004 Share Posted July 20, 2004 11,250,000 - Torsional Modules For Steel (Constant) CSPWD - Coil Spring Wire Diameter (How thick is the wire?) 8 - Constant NOAC - Number Of Active Coils (Coils that are free to move. Not coils seated. It may be that 1/2 of the top and bottom coil is seated causing a spring with 8 coils to have the distance of 7 free.) CMD - Coil Mean Diameter (The diameter from center to center of the coil. Measure the diameter of the coil from wire center to wire center. If you know the coil is .5 inches thick and the outside diameter of the coil spring is 3 inches, then the Coil Mean Diameter would be 2.5 inches) (11,250,000 x (CSWD x 4)) / (8 x NOAC x (CMD x 3)) Quote Link to comment Share on other sites More sharing options...
Jersey Posted July 21, 2004 Author Share Posted July 21, 2004 Thanks John. Quote Link to comment Share on other sites More sharing options...
Clifton Posted July 22, 2004 Share Posted July 22, 2004 Or if you have a press you can stick one in it on a bathroom scale and compress it down an inch and see what the scale reads. That's what I did. Quote Link to comment Share on other sites More sharing options...
Jersey Posted August 7, 2004 Author Share Posted August 7, 2004 What the heck am i doing wrong? While replacing my struts tonight, i took some spring measurements. Here's what i came up with: CSPWD = .5 NOAC = 7.5 CMD = 3.875 so.... (11,250,000 x (.5 x 4)) / (8 x 7.5 x (3.875 x 3)) = 22,500,000/8 x 7.5 x 11.625 = 22,500,000/697.5 = 32258.06...? Quote Link to comment Share on other sites More sharing options...
johnc Posted August 7, 2004 Share Posted August 7, 2004 I goofed and I think I posted the calculation for stress. Here's the right one: rate = ( wireDia^4 * 1470000 ) / ( coilDia^3 * numCoils ) "^" means: to the power of. Using you numbers above we get: (.5^4 * 1,470,000) / (3.875^3 * 7.5) = 210 lb. in. Sorry. Quote Link to comment Share on other sites More sharing options...
Dat260 Posted August 7, 2004 Share Posted August 7, 2004 Hi Johnc, This is good information, should be in the sticky section. Ari Quote Link to comment Share on other sites More sharing options...
Jersey Posted August 7, 2004 Author Share Posted August 7, 2004 Well, then... it looks like they can handle a heckofalotta stess! lol. Thanks again John. Great help. Now i need to see if the valving in the KYB's are too light and just can't handle a 210lb spring rate. Completely blew out the seals in the last set. Quote Link to comment Share on other sites More sharing options...
johnc Posted August 8, 2004 Share Posted August 8, 2004 Blown seals sometimes are caused by the shock bottoming or topping out. Are you running bump stops? Quote Link to comment Share on other sites More sharing options...
Jersey Posted August 8, 2004 Author Share Posted August 8, 2004 Running stops and these are the rear which never bottom. With my old Eibach springs, the KYB's seemed fine. A week after i swapped these stiffer springs in, the seals blew leaving a big mess all over the rear suspension. I guess we'll see if these hold up. BTW, a blown strut will make the @ss of a Z shift alllll over the place. Amazing how much it affected the response of a slight bump. Thanks for all the help and responses. Quote Link to comment Share on other sites More sharing options...
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