I posted something similar when I first joined the forum, but maybe someone has researched this further since then. I am trying to determine certain perameters in the suspension systems of the sedan and coupe. As we all know, the coupe is lower than the sedan, but I believe there are more differences than that between the two systems. I have the service manuals for the two vehicles, and have noticed this: The coupe seems to have more bracing for the front and rear suspension members. The front has the most noticeable difference; it has a tubular brace that seems to tie the suspension member and the chasis together, thus reinforcing it. The sedan does not have this (according to the manual). This could prove to be a major advantage (as far as deflection goes) between the two.
I am also trying to determine where the roll centers are for the front and rear. I believe that the suspensions are essentially the same (bolt-on sub systems). Unfortunately, the manuals do not provide part numbers for the larger parts, so I can not compare. If this is true, however, then we can assume that lowering the sedan to coupe specs will not harm overall handling due to roll migration from lowering the roll center too far. If this is not true, then I question how far we can lower the sedan before we run into issues with body roll, as well as bump steer, excessive understeer, etc. (Anyone who has experienced bump-steer due to lowering the vehicle please let us know). I just want to know how much room there is in the factory tolerances. I am also curious as to which roll center is at a higher plane, the front or the rear? This would help determine how far to lower the vehicle for optimum handling. If anyone knows any information that may be helpful, please let me know. My goal is to come up with the optimum suspension setup for this vehicle. Thanks for any help.

'03.5 Brilliant Silver AT Sedan, Premium, Aero Kit/Package, Sport, Winter, Stillen Air Box, Z pipe, Clear Corners, Alum. Pedals, Polk Tweeters, Clifford RSX 3.5, Gram Light 57F Pro's (on the way!)

 

hmm, i dont know about your specific questions, but i have the 350Z suspension on my car, lowering it 7/8 in front and 1 1/8 in back, and there is no bump steer. as for the body roll, i have gotten used to the reduced body roll and now it seems too much again. although wwaaaay better than stock. please post your findings if you ever get any.

G35S 6MT
Technosquare ECU
350Z Springs & Struts
6-wire ground kit

 

I am sure we could get extended tie rod ends for the bump steer problem, if we ever encountered it. There are many companies that make them. What I was saying about body roll is, yes, it is reduced when you add stiffer springs and sways, but this is more of a "band-aid," rather than a fix when lowering a vehicle. The sways and spring rates should work WITH the suspension, instead of over-compensating for it's lack of correct suspension geometry. I want to see how much room we have in the geometry before it gets thrown out-of-whack. Thanks for the post. Anyone else?

'03.5 Brilliant Silver AT Sedan, Premium, Aero Kit/Package, Sport, Winter, Stillen Air Box, Z pipe, Clear Corners, Alum. Pedals, Polk Tweeters, Clifford RSX 3.5, Gram Light 57F Pro's (on the way!)

 

still a very intersting topic. maybe if you post this in the FA forums or the mod forums, more people will see it. i dont think that many people view this specific one as often.

G35S 6MT
Technosquare ECU
350Z Springs & Struts
6-wire ground kit

 

ttt

'03.5 Brilliant Silver AT Sedan, Premium, Aero Kit/Package, Sport, Winter, Stillen Air Box, Z pipe, Clear Corners, Alum. Pedals, Polk Tweeters, Clifford RSX 3.5, Gram Light 57F Pro's (on the way!)