You should probably get a least some better lower control arms but the biggest issue is this:
The factory springs were meant to work as a system and together just like the Steeda Sports. Despite the factory hardware not being exactly brilliant, they do complement each other just like the Steeda springs do. The spring rates are all out of wack. Plus your rake has increased as well, throwing off the dynamics of the car. Because of this, your car is now very front domant in geometric balance. Choose one: factory springs all around or the Steeda springs all around.
Yeah! I hear you. The Sport springs dropped the front end only about a ½ inch, while the rear dropped by a full inch. Car was levelled, no rake, and that did not look good at all and did not handle well either, creating understeer. To get the original rake, the Sport springs would need to be a ½ inch taller. So to use the Steeda springs in the back, i would need ½ inch spring spacers and i don't know if that would be a good idea or where to look for quality parts. I have also been looking at the Route 66 Speedshop MUSTANG 55D SPRING KIT as those would lower about ½ inch with a spring rate closer to the Steedas than the OE spring.
Steeda now warns buyers about the light V6 in the 2011+ and do not recommend the use of Sport Springs.... but that was not the case when i purchased my springs.
The front end is great, so i would prefer fixing the back instead of going back to stock springs in front. Swapping rear springs is also a quick and painless operation.
Keep the comments coming, my Mustang handles great, but i need to tweak the rear end.
Canadian 2012 V6, MT, Perf.White Pony Package (3.31 gears). Koni Sport Shocks & Struts. Steeda Sport Springs w/HD Mounts, Route 66 SpeedShop 55D rear spring kit. Boss 302 Strut Tower Brace. BMR Adj PHB. BFG G-Force Sport Comp2. Pioneer TS-D6802R Front SPeakers, Clarion 80W/Ch Amp. JL Audio 8 Inch Sub And 175W Amp. GT500 Steering Wheel. 2012+ Tilting Headrests