Quote:
Originally Posted by frojoe
Just to avoid misinformation, there are essentially 3 lengths of springs available for our cars and all have vastly different spring rates:
1) Stock spring (uses spring pockets on subframe as well as LCA's) I believe is in a 12"-14" range (changes depending if OEM vs aftermarket vs aftermarket lowering, etc) and are generally quite soft (200-300lb/in?)
2) Traditional design "conversion coilovers" like QA1/Viking that re-use the subframe spring pocket however have a threaded collar on the shock body to support the bottom of the spring. These are in the 10-11" uncompressed length if I remember correctly, and usually have spring rates available in the 350-550 range (for our cars 400lb/in is quite soft and 350lb/in would almost be undriveable)
3) Newer "coilover conversion" design like the Ridetech, where the spring is entirely captured by collars on the shock body and the shock itself has a Tbar mount on the bottom and a pillow ball like upper stud mount. Because the spring is entirely captured on the shock body, and has to clear the subframe as well as the LCA, the spring has to be a much shorter uncompressed length of 8" in order to clear everything (spring rates available from 500-800lb/in)
The shorter the spring gets, the higher the spring stiffness needs to be to get the same ride quality (obviously as the spring gets shorter, then available travel also decreases).
When I switched from QA1's with 10" 450lb/in springs to the same control arm setup but with 8" 700lb/in Ridetechs, for curiousity sake I calc'd that the equivalent rate of the new springs would've equalled ~430lb/in if in the length needed to fit the old QA1's.
Rod P's setup of 750lb/in 8" springs is now what I'm running, and that should have an equivalent ride feel to maybe a 475lb/in spring that is the proper length to fit a QA1/Viking conversion coilover, or maybe a rate of ~325lb/in for a stock-suspension length spring.
When you ask what peoples' spring rates are you have to take into account the length of the shock they're using, for stroke as well as uncompressed overall spring length.
-Joe
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Um, spring rate is spring rate, regardless of spring length. It still takes 'x' pounds to compress the spring 1 inch.
However, the
wheel rate can be affected if the top and/or bottom of coilover 'x' is mounted in a different spot than coilover 'y'.