IW STi Forum banner

08 STi Factory Spring Rates?

16K views 18 replies 7 participants last post by  PGT  
#1 ·
Hey guys, I've been looking for a while now. Does anyone know what the F/R Factory Spring Rates are on the GR STi? Looking for an answer in lb/in but any answer will do (kg/mm is cool too).

Thanks,
Steven
 
#3 ·
I posted this about a month ago in this section. Thread title was pretty much the same as yours as well. I would give them to you now, but don't have them on this computer.
Is this what you are looking for TiC?
Front spring rate: 38 N/mm ~ 217#
Rear spring rate: 34 N/mm ~ 194#
 
#7 ·
Crazy that the spring rates would be nearly identical to earlier STI's even though the motion ratios are different. To make an old STI feel like the new one, replace the rear springs and dampers with parts from a WRX. That's close to what Subaru's new setup is when measured at the wheels.
 
#15 · (Edited)
Wheel rate = spring rate * motion ratio ^ 2.

So if you have a 100lb/in spring with a motion ratio of 0.5, your wheel rate is only 25lb/in.

This is because for every inch of wheel movement, the spring only compresses HALF an inch. Additionally, the wheel has leverage over that spring, so it only needs to exert 50lbs for every 100lbs of resistance at the spring. Thus, you multiply the spring rate by the motion ratio twice to get the wheel rate.


Edit: Can anyone confirm that the motion ratio in the rear is 0.8? I don't own a GR. I thought Turn-In Concepts measured this, but I searched and couldn't find it. I hope I'm not completely making that number up, but my mind has done stranger things before.
 
#18 ·
so then that means..assuming a similar weight distribution from the GD to the GR, A typical coilover springrate of 500/400 (9kg/7kg) (ie RCE T2), for the GR would need to be 500/625 (9kg/11kg) in order to behave similarly. true?
why don't GR coilovers come like this then? and would revalving be necessary to support the rear spring rate...