How to check the condition on springs? How can I know that is it good or bad? Please give me some idea.

 

Coil springs don't really go bad...it's usually the shock that fails...

 

I mean the stock or aftermarket springs.

 

Well, if they are visually okay, and you're still not satisfied, you can remove them from the shock/spring assembly and send them to someplace like Truechoice or maybe Ground Control. They have machines to measure spring rate. But if you're going to do that, why not just order new springs in the rate that you want?

 

I have a really newbie question to ask... Why do people change stock springs for aftermarket springs? i know they want stiffer... ie high spring rate constant... but doesn't the shocks also determine how stiff your car will be?

 

because I want to buy a set of used springs.

 

Cheers,

Wow you just gave yourself away about how little you know about suspension

Shocks are dampers. They control the springs. People switch out their OE style (4-inch outder diameter) springs to lower the ride height and increase the stiffness. When you get stiffer springs, you need stiffer shock damping to control the stiffer springs, otherwise your car will oscillate (move up and down) uncontrollably over bumps!

With new 2.5-inch springs shocks, you can now adjust the stiffness and ride height based on track surface conditions.

I recommend you do some reading. Carrol Smith's Tune to Win would be an excellent introduction to suspension tuning.