Friday, Mar 30, 2007 at 08:46
Sorry I didn't make it clear that it's 200 lb/inch for each spring. Two springs = 400 lb/inch total, that's why it'd only be about 1/2".
Progressive springs are would with unevenly spaced coils. The wire size is the same all the way round, it's just that the more closely wound coils close up first and so the spring rate increases with load. A straight-rate spring has evenly would coils - all coils will close up at the same time, at the limit of compression.
Spring spacers simply raise the vehicle and the spring rate is unaffected. Polyairs are like adding another spring in parallel and so increase spring rate. An increased spring rate will reduce overall wheel travel.
You can think of adding spacers as fine-tuning. They are available in lengths as short as 10 mm and let you make small adjustments to the level of the vehicle, eg where you have an additional fixed load that is not great enough to justify jumping to the next available spring rate or length.
Polyairs are more to allow for larger variable loads, so you can adjust ride height depending on load.
If you raise the vehicle too much with spring spacers you may need longer shocks or travel limiting straps or you may need to extend the bump stops, just as if you fitted different springs. 30 mm should not be a problem with a landcruiser.
Firmer springs/polyairs are more appropriate than spring spacers if you are bottoming out regularly, or if you just want a firmer ride on the bitumen.
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