Thanks again Ross. It is surprising. 4 inches of total movement is about all of I'd expect it to move in use and it's doing that with only 900lbs. Any more and the axle is on the frame. 4.5 inches is about as much as I'll get from a shock absorber. And an inch of that is a bump rubber.

 

I would also believe that you would have to take into consideration that you have the poly liners which would reduce friction thereby allowing the springs to deflect more than without them. But then again what do I know.

 

For that to be true the stock spring pack would need to have been measured with a substantial amount of friction in order to give the 225 lb/in figure supplied by Ross. They would have been new steel and most probably oiled or graphited. If I manage to source some then we will soon see and I'll put it here. There seems to be an issue getting them though. There is a Chinese version, quality unknown. Or there is US version which were very high priced in comparison, availability unknown. Waiting to hear.

 

I talked to a guy at Eaton. He wasn't their engineer, but seemed to know what he's talking about. I asked if it was possible that the springs could lose their rate, but still have close to their normal arch. He said, Yes, we have had rusty old springs that are shot in house, taken them apart and they still have their arch, but no strength. I asked if the liners would affect spring rate, he said no, neither liners nor "buttons" (on the ends of the leaves) change the rate.

He said he couldn't say whether losing 50% of rate was possible, seemed surprised it was that much.

I am left with the feeling that what you have are not stock springs, but replacements that were cheaply made (not heat-treated enough), or made for lowering or softening the ride. If you want new ones, they make them to order (they don't stock them), said it would take a couple of weeks from ordering date. I have to believe someone on your side of the pond can make you a set for less money and without huge shipping costs.

 

I really appreciate you going to that effort Ross. Thanks mate. I don't know if they could have come from somewhere else. I guess they could be from a similar vehicle but with such low stiffness they would be of little use to almost anything. The truck showed signs of neglect but was otherwise remarkably original. One odd thing I did notice when I was checking the frame for straightness was that the wheelbase was only 109 inch. But since it was equal both sides I didn't think too much about it. By that stage, the rear fenders were off so not sure if the rear wheels were centred. Maybe that was a sign something was not as it should be because I think it should be 110 inch.

I phoned the company who made my U bolts today and the guy said he would likely be able to do something for me. Which will involve manufacturing new ones, re-tempering the old ones or adding leaves. He did say it sounded like the re-tempering probably wouldn't be enough because of how much they have lost. So I will pull them off tomorrow and send them down to him to see what my options are. At least now I have all the info I need to make them. Thanks again.