Ascertaining Spring Rates?

[Fluoxetine]

With springtime nearly here, I'm about to dust off the fancy Tein coilovers I bought for my shed last autumn, and actually fit them to the car.

(All the talk of CLCM reminded me... )

Anyway, I ended up with x2 sets of springs when I purchased them - The standard set, and another set the previous owner had bought, which he reckoned were a lower spring rate than OEM.

Unfortunately he couldn't recall the rate - And there's no serial / part number on them...Just a little 'Tein' logo...

Anyone know of anywhere with a rig that can test spring rate?

TIA!

[robin]

It's easy to compare relative spring rates if the springs are loose (i.e. not assembled onto dampers, etc.). All you need is a known (preferably quite heavy) weight, e.g. a stage weight like the ones that are in Lawrence's garage. Measure the unladen spring length, then put the weight on and measure the length again (or at least mark it on the wall/door/piece of cardboard). Repeat with the same weight on each spring you have in hand. The one that deflects the least is the strongest spring. If you want to know the actual spring rate you'll need to measure the deflection and know the weight of the object you're using.

As springs are measured in pounds per inch (yuck) you might as well know the weight in pounds, and measure the deflection in inches. Then if you put on a 30lb weight and the spring compresses 1/10" of an inch you have a 300 lb/in spring. At least that's what I think ...

If you're struggling for something heavy enough, use a plank of wood over a pair of springs, then stand on the plank and mark the before-and-after heights on the wall with a marker

Cheers,
Robin

[campbell]

Fascinating !!

[Fluoxetine]

Cheers Mr Fisics!

That makes sense, and seems fairly obvious when you now think about it...

Quite bizarrely, Tein quote their kit spring rates in kgf/mm - Think the standard kit (already on the coilovers) works out at F- 392(LB's per inch) R- 336...Be interested to see what the other set measure at...

[robin]

kgf is unit that means a kilogram as a force ... (kilogram is a unit of mass really, but when subjected to gravity it becomes a weight which is a force).

For normal use (i.e. anywhere on earth ) you can treat kgf to mean kg, so 1 kgf/mm = 1 kg/mm = 2.2 lbs/mm = 56 lbs/inch. So 392 lbs/inch = 7 kgf/mm and 336 lbs/inch = 6 kgf/mm.

But I may be totally wrong

Cheers,
Robin

[Rich H]

lb/in makes old skool sense but Kgf/mm is just daft!
No doubt thought up by the marketing dept who thought that the numbers sounded better like that...