# How can I soften a spring rate?



## Handy Dan (May 13, 2011)

I have some after market disk brakes on the back wheels of my truck and the return spring for them is made for a car that has a foot actuated e-brake and mine is an old Toyota pull handle under the dash.

How can I soften the spring so I can set the brake and not feel like I'm trying to pull a semi truck down the road with by hand?

Do I heat them up and just let them cool? I don't want to cut them because I need the full spring height so they fit properly (and they'll still be too stiff anyways).

TIA


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## ukrkoz (Dec 31, 2010)

if you cut a spring, for the same length it will still have to work through, you'll make it STRONGER.

you can anneal them.

http://www.efunda.com/processes/heat_treat/softening/annealing.cfm

i am not sure to what specific hardness yours supposed to be. back from my tool maker times, we kept springs at about 50 Rockwell. springs are made out of special spring steel. they were brought up to about 870 C and dropped into room temperature oil. annealed to dark brown.

this is what i am referring to:

*Stress Relief Annealing*








*Stress Relief Anneal* is used to _reduce residual stresses_ in large castings, welded parts and cold-formed parts. Such parts tend to have stresses due to thermal cycling or work hardening. Parts are heated to temperatures of up to 600 - 650 ºC (1112 - 1202 ºF), and held for an extended time (about 1 hour or more) and then slowly cooled in still air.


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