21A1806 Hydrolastic Helper Springs 3

Measuring the Spring Tension (Take 2)

After measuring the NOS springs, I decided to the remove the right hand side spring (as it’s the easiest to get off) and profile it and the NOS spring using a different method.

What I did was to mount a Craftright Quick Action clamp in my vice with the movable clamp reversed so that when you moved the grip it went up the clamp rod so that it extended the spring along with the digital scale. Anyway a pictures worth a thousand words so here is some pictures.

Bottom of spring. Note black instead of orange… any ideas folks as to why?
Primitive indicator on top of spring. Don’t knock it, it works!
Top attached to bottom of spring scale.
Top of spring scale attached to movable clamp handle.
Don’t get any ideas about pinching my patented steady method!

I found the new and improved method a lot more repeatable due to the very fine movement offered by the grip handle. If you were wondering what the rope was for at the top, it’s to stop the thing flexing, and giving inaccurate results!


The measured spring rate of the old spring was 29.9lb/in a 5.2% difference. Not a vast difference at all. One thing is the old spring that came of definitely does not look like it is a 47yo spring, so maybe they have been replaced in a former life.

I will be looking at replacing both the front upper suspension arms (yes including the elusive L/H one which I’ve managed to source NOS), as these were repaired after the suspension knuckle wore the holes. The repairer at the time used some sort of epoxy to fill the holes. Unfortunately he didn’t shim the knuckles, with washers, to bring up the ride height. I also suspect the hydro bags have sagged, but other than swapping them for the rears, there is nought I can do.

Finally if anyone wishes to send me an known old spring so I can measure it that would be great.

Here is the Spreadsheet: Hydrolastic Helper Springs

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