Understanding spring rates


#1

Stop guessing at what springs to use. Soft or stiff are relative terms that really don’t mean a great deal. Get some base line data for what you have with this online spring calculator and figure out what you really need. In relative terms with front to rear difference the end of the car with softer springs will have more grip. So if you have understeer then stiffen the rear (yes sway bars can alter such dynamics too but it’s best to start with springs).

http://www.acxesspring.com/spring-pitch-calculator.html


#2

Thanks Mr Gromsby, once again I appreciate the lesson.
I have punched in the spec to the calculator and have discovered the springs from the Hi-Jet that are in the L60 are massively too stiff at 240 lb/inch.
I am slowly working out what I want and know the standard L60 spring rate is about 80lb.
Thanks.


#3

How do we know What the springs are made out of for this calculator ?


#4

If you have looked at the calculator it gives you the option to choose from a range of materials. It’s up to you to determine what your springs are. Normally 5160, 9260 or some sort of high-alloy low carbon steel. Just use the default in the calc if not sure. Compared to having “no idea” on rate it will provide a ball park figure. If you are really anal and worried that ordering a replacement would be a problem then the calc will at least give your percentage rate diff front to rear (assuming orig springs are factory or from same manufacturer). Then go and order a front and rear set from the same place with a diff percentage split.

You could take one of your springs to a lab that does x ray fluorescence testing and pay for their services.

To know the rate “for sure” I use a friend’s load cell that is set up in a hydro/pneumatic press just for this purpose.

If none of that works for you just go back to the subjective feel of “hmm that feels soft/hard”.


#5

Here is some more useful information regarding springs and showing other formulas for load, spring rate ect.
https://www.acxesspring.com/compression-spring-calculations.html

Here is a list of OEM springs by moog showing all specs and dimensions, the part numbers can be cross referenced with other OEM spring manufaturers
http://www.moog-suspension-parts.com/universal_coil_springs.asp


#6

Some more useful info on handling below.

It is always interesting seeing on facebok the "did it ‘cause it looks cool bro’ " mods. A little knowledge is dangerous. Just because you find some low springs and or have a cut off wheel on an angle grinder does not mean you should put those S13 springs in. And the huge wheel offsets that look good in a photo are a big step backwards - not just from a performance point of view but also an awful thing even to drive down the shops for milk.

https://l.facebook.com/l.php?u=http%3A%2F%2Fwww.morsemeasurements.com%2Fwheel-lift%2F&h=ATMtWhjy_Adb7l1VHIUKoZEgVAjCH1fWj-3EKbpVOdRy8_sf77Yr6BzWqCJ4TqhN8zbE_wPb8maF2BcEZAaSCmShtrY4e4mu5UeSqxhigS2iSJD3hw&s=1


#7

A great rescource for fine tuning suspension, the tables describe how different adjustments affect how the car reacts. Great for Troubleshooting.
http://www.rapid-racer.com/suspension-tuning.php