4kq

[Jason Gray]

Doh... I knew that about under/oversteer, just typed too fast. I stand corrected, stiffer front springs should normaly increase understeer, not oversteer (thus the suggestion of adding the R Swaybar). 

I maintain that the advice in the archives concerning relative front/rear spring rates for the 4kq is flat wrong and there is also plenty of advice in the archives to support the assertion that front springs are stiffer than rear.  My firsthand observation is that the two different stock 4Kq I have check out had stiffer rear springs than front. Use a vernier caliper and you can easily check that the wire diameter of the rear springs 0.527" is larger than the wire diameter of the front 0.504" springs. Rear springs have 5 active coils, front springs have 6 active coils and the OD of the coil is 5.75". Plug this into a spring equation and you can derive the approx spring rate;
http://www.kaila.net/tl125/spring.html 

The stock rear spring rate for the 4Kq is right around 45% stiffer than the front spring rate. I completely agree that the factory spring selection was poor, all the more reason to change it.  I would bet that the spefications for the 90q front springs are closer to the 4kQ front springs than the rears (softer). I would invite anyone with actual measurements of the 90q spring to share them (measure the wire diameter and # of free coils). 

-Jason Gray
Anchorage AK


  Message: 5
  Date: Wed, 17 Mar 2004 15:47:20 -0500
  From: "Brady Moffatt" <bradym at sympatico.ca>
  You sure about that? The hot setup is supposed to be 90q front springs on
  the front, and 4kq front springs moved to the back. Intuitively, front
  springs should be stiffer, due to their supporting almost 60% of the weight
  when the car isn't even moving. Throw in weight transfer under braking and
  cornering and that percentage goes even higher.

  Unfortunately, this mod raises the car. Not what was being sought in the
  original post. Hmm thread creep happening again!

  This has been discussed before. Check the archives.

  Cheers,
  Brady
  Urq, 4kq, Z