66 front spring.

[bbp]

Do i use a factory spring or a shorter performane spring? Any one good advice? Some one must have tried these both.

 

[Chainshot]

The newer shorter ones are way easier to install compared with the taller originals. I would go with the new shorter ones in the spring rate that I desired.

 

[JohnZ]

To achieve the same ride height, a spring with shorter free length will have a much higher rate (like F-41 springs); if you want shorter free length just for ease of installation, be prepared for more ride harshness. Seems like a bad compromise long-term just for a slightly simpler one-time installation.

 

[Chainshot]

Hmm...I thought the diameter of the wire made up the spring rate ? Shorter but with a thicker dia. wire made them equal to what you are replacing.

I can't question Johnz though. He is THE man.

 

[Tom Bryant]

I think that is just what John was getting at. If you want the same installed height from the shorter spring as you would get from the longer stock spring, resulting in the same ride height, you would have to have a thicker diameter wire on the shorter spring. This would give it an increased spring rate and make it ride harsher. Spring rate is not solely determined by the wire diameter. It is also determined by the total length of the wire. If you were to take a tall stock spring and simply cut off a couple coils to shorten it you would also be increasing it's rate. For any given diameter, the longer the wire the easier it bends.

Tom

 

[Chainshot]

That makes sense - I hadn't even thought about the difference in ride height. I remember a terrible wrestling match trying to stuff my original springs back in and others talking about the newer, shorter springs and how much easier they were to install.