Join Date: Nov 1999
Location: Central California, USA
Re: Multi-leaf spring isolator pad query
The stock shackle length is critical to stock spring performance. It's length and installed angle does a lot more than people realize. It provides a rising spring rate in compression for mono-leaf and multi-leaf springs. If you install longer shackles, the spring rate does not rise as fast as designed. If your springs sag, the shackle angle changes and the spring package delivers a stiffer rate. I'm not saying aftermarket shackles are no good, but they should be stock length hole to hole to work as the manufacturer intended.
Mono leaf springs only have a register welded to the bottom of the leaf and if not clamped tight enough the axle can slip forward on the leaf and tear the pads. The mono-leaf lower spring plates are thinner than a multi leaf plate and tend to bow when tightened so they are not capable of clamping the leaf spring very tight. They also can crack more easily, probably due to flexing. I prefer to use a spacer or thin lowering block on top of the leaf and let the leaf register fully engage the hole in the spring plate so the axle does not slip.
Check my web page for First Gen Camaro suspension info:
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67 RS 327 original owner. 1965 Lola T-70