How to measure spring rate?

[DavieSV]

Hi all.
Any one know how I can measure the spring rate using scales?

I have put a spring on some scales and slightly compressed it.
zero'ed readout.
Compressed it 10mm and the scales read 70kg,
Compressed it another 10mm and the scales read 149kg.

Can anyone determin the spring rate from these figures or am I just barking up the wrong tree

I cannot compress the spring any more because the scales will only go to 156kg.

Ideally by taking it to someone who has a spring tester. If you post it to me and cover the return postage I can do it for you on ours.

[andrewsmith]

best to get done on a test rig.

Is it a stock shock by any chance?

Originally Posted by DavieSV

Hi all.
Any one know how I can measure the spring rate using scales?

I have put a spring on some scales and slightly compressed it.
zero'ed readout.
Compressed it 10mm and the scales read 70kg,
Compressed it another 10mm and the scales read 149kg.

Can anyone determin the spring rate from these figures or am I just barking up the wrong tree

That is the way, spring tester is scale. You just need precise way to measure compression of spring. 70kg for 10mm would be 7.0 spring.

Don't know what rate you want, but it works out to be ~415lb/in which is a standard spring rate measurement which you could convert to any other standard rate easily.

Actually ~390lb/in

Originally Posted by zadar

Actually ~390lb/in

Depends which scale measurement you take:

149kg = 327lb for 20mm compression

20/25.4 = 0.7874

327/0.7874 = 415.29lb/in


70kg = 154lb

10/25.4 = 0.3937

154/0.3937 = 390lb/in

We just use 55.88 for conversion factor.
(1kg/mm)*(25.4mm/1in)*(2.2lb/1kg) => 1 kg/mm = 55.88 lb/in

[DavieSV]

The spring is off an RSVR which I replaced my standard shock for a while ago.
I thought the standard spring was around 600lb, so I was expecting readings of around 105 @ 10mm and 210 @ 20mm.

Although it handled OK with this spring on and I could set the sag spot on, I was a bit worried about it being too stiff.
I replaced the spring with a 475lb spring I got off 21Quest, Setting the sag was only just within recomended limits and under hard acceleration with just a tail pack on, it squats like a jipsy who's drunk too much tea.

I have now got 1.0kg springs in the front so was considering putting the stiffer rear spring back on but thought I would try and determin what rate it actually was.

I think the scales are pretty accurate (but they have not been calibrated for years) and the displacement was crack on, I used the quill of a vertical miller to compress the spring and used slips to set the distance.

RSVR as aprilia 1000? those are usually in 500lb range for race bike with lighter rider.
If you using 1.0 in front you should be around 550 on rear.