cab

I know the vast majority of discussion on this forum revolves around the F-bodies (which I've owned three of), but my question is a both more generic and specific to my 2005 GTO. The late model GTOs are generally acknowledged to be under sprung from the factory. Stock springs sag, and it is pretty common over medium or larger bumps to have them crashing into the bump stops, etc. The rears are generally considered to be worse than the fronts. To that end I swapped out my springs for Lovells STOCK HEIGHT aftermarket springs. These springs are NOT drop springs - they are stock height. They are however, a higher rate spring as follows:

Stock Front Spring Rate: approx 150 lbs (linear)
Stock Rear Spring Rate: approx 300 lbs (somewhat progressive)

Lovells No drop Front Spring Rate: approx 165 lbs linear
Lovells No drop Rear Spring Rate: approx 400 lbs linear

For you F-Body guys - don't freak out at the high rear rate. The suspension geometry on a GTO is totally different - the springs sit at a bit of an angle, away from the wheels etc. 400 lbs is considered a "soft" street spring in the GTO world...the "serious" guys run 500+ lbs and the really serious guys much more.

Anyway, the factory struts/shocks are made by Monroe and are oil/air in the front strut and a oil/gas shock in the rear. When I replaced the springs (at 29K miles) I went ahead and tossed a set of Monroe Sensatracs on both ends. Yes, Yes I know these are not "performance" shocks. However, they are at least a slight upgrade in that a.) they are new, and b.) the front moved from an oil/air setup to oil/gas.

From a ride perspective my car no longer bottoms out (i.e. crashing into the bumpstops) when going over medium or larger bumps, and it certainly handles better. Over smooth freeways it feels virtually stock. However, at freeway speeds when I hit a bit of a whoop-de-do type of bump I am practically thrown into the air. At low speeds (this is even more aggravating) if I hit series of mild bumps a few feet apart the car seems to almost start "rocking" back and forth. I am wondering if the car is underdamped, especially in the area of rebound and while the compression stroke of the shock is OK, the Monroes are having trouble controlling the speed of rebound of the higher rate spring causing the spring to essentially over extend instead of simply returning to the cruise ride height in a smooth controlled manner. If I am correct, it would appear a dampener (particularly in the rear) with a tighter rebound would benefit the ride...although perhaps at some expense to the compression stroke and thus impact harshness. Any thoughts on this? Am I even remotely on the right track? I don't want to drop a bunch of coin only to find out my logic was flawed.

Thanks,

Chris

Magic Man

I think what you did was put heavier springs but still have a stock shock and the springs are stiffer to keep from collapsing on bumps but the rebound is a lot faster than the shocks can control and they aren't working on compression well either.All of this is what you basicaly said but you could put on some heavier shocks but how much so you might try some adjustable ones where you could set for the springs which with the springs will stffen up the ride.Or you could just put on some stock type springs and probably be where you want on the ride.Now that I'm lost I hope this is ok and helps you.

cab

On single adjustables (i.e. Konis) does the tightening of the rebound alter the compression or is the compression a constant? Any other opinions on my situation?

Magic Man

On the single adjustment it is on both as you adjust up the compression and rebound get stiffer.