Eibach pro kit lowering springs installed, passenger rear side sits 7/8" higher than driver side.

[07 Boss]

It is actually a proven fact that they should e facing a specific direction. Even Eibachs directions talk about spring orientation. I personally have experienced this issue myself.

Eibach instructions talks about the the up and down orientation of the springs. The rear springs are coiled differently on the top and bottom and the instructions tell you to have the logo being right side up to make sure the tighter wound coils are up top. Rear shock perches are flat and have no relief for the pigtail of the coil. Ride height will not change no matter which way you orient the spring. Front springs are different because the the pigtail has to sit properly in the perch to acheive the proper ride height.

 

[86GT351]

Eibach instructions talks about the the up and down orientation of the springs. The rear springs are coiled differently on the top and bottom and the instructions tell you to have the logo being right side up to make sure the tighter wound coils are up top. Rear shock perches are flat and have no relief for the pigtail of the coil. Ride height will not change no matter which way you orient the spring. Front springs are different because the the pigtail has to sit properly in the perch to acheive the proper ride height.

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On a Mustang, the rear coil springs should be installed with the "pigtail" (the small loop at the end of the spring) pointing towards the driver's side of the car; this means both rear springs will have their pigtails oriented in the same direction, towards the driver side, ensuring proper alignment and function.

Key points about Mustang rear coil spring orientation:

• Pigtail direction: The pigtail should always face the driver's side on both rear springs.

 

[07 Boss]

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View attachment 102826
On a Mustang, the rear coil springs should be installed with the "pigtail" (the small loop at the end of the spring) pointing towards the driver's side of the car; this means both rear springs will have their pigtails oriented in the same direction, towards the driver side, ensuring proper alignment and function.

Key points about Mustang rear coil spring orientation:

• Pigtail direction: The pigtail should always face the driver's side on both rear springs.

Installed/swapped springs at least a dozen times, twice with eibach and I've never seen that in their instructions or any other brands I have installed. I have never oriented my rear springs. I can guarantee you though that clocking the springs will have zero effect on ride height.

 

[Autokyrios]

Sorry, my brain was latched onto my current coils which are flat. I don't have my stock rear seats anymore, but I don't recall the seats being shaped. Either way, I do have one of the old springs and the coil seems nowhere near thick enough to cause that kind of deviation if the end wasn't sitting right. Little, maybe, but this is nearly an inch, right? I'd be more inclined to think the coil orientation has more to do with compression characteristic than idle height.

I'm still with swapping them left to right and seeing if there's a change. Or throwing the stock springs back in and seeing if it goes back to normal.