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Originally Posted by sewin
Firstly being able to turn the rebound springs by hand at static load is frankly rubbish. As far as I'm aware this all came about when suspension systems were being messed with and to make the older steering as light as possible rebound springs were being shortened to suit the car and reduce steering friction, the guide then was.... should be able to turn it by hand at static load! This is not applicable now to the later steering systems with no damper blades and bearings. If you see a suspension system hung up and the hub carrier sitting clear of the rebound spring the issue will lie with either: worn pins/bushes, lack of lubricant or overly weak main springs, Possibly a shortened rebound spring if you let a muppet loose with his grinder!
Lack of correct lubrication within the hub is a very real problem as firstly the hub will fail to slide effectively on the pin. any ingested grit will not be effectively expelled as the suspension will not be able to expel a small amount of grease on the larger thumps to the suspension. This is why Morgan have always recommended what seems to be an over regular greasing regime, It can't need that much grease but it needs the pressure from within to maintain longevity by cleaning the inter bearing face.! In normal use the suspension will frequently find the hub lifting clear of the rebound spring.... it's meant to work like that and the rebound springs function is to damp the hubs return as the main spring pushes the hub back down. These springs are matched pairs... well should be anyway and are designed to work in harmony as a unit. This system was introduced way before shock absorbers were invented. Read H.F.S.'s explanations and then Peter Morgans story of why he installed front shocks!

My own understanding is that rebound springs were historically shortened as a bodge (as per CBY post) to reduce static pre-load on rebound springs which in turn resulted in the fact based massively high spring rate of having both springs in play. This in turn causing uncomfortably hard suspension but then sagging into corners due to inside main spring compression taking rebound spring out of play and effective spring rate reducing to that of main spring alone. Several owners and at least one magazine test of Plus 8 brought this fact to light many decades ago. Peter Ballard explained it and mentioned that ironically as main springs weakened with age the issue could dissapear. Suggesting the rebound pre-load test is rubbish for an entirely different and less important reason is not a fair comment. Its as relative today for trads as ever.


Richard

2018 Roadster 3.7
1966 Land Rover S2a 88
2024 Royal Enfield Guerrilla 450
1945 Guzzi Airone