non-lowering rear springs??

Eibach drag launch springs aren't supposed to lower the car at all

Mach 1 springs with polyurethane iso's dont lower a fox much at all if any.

As others have stated, if you just want "fresh" new springs in there, don't bother - keep the ones you have (as long as their not damaged) - they don't really "wear out".

If you want to changing the handling characteristics, go with the Mach or Bullitt springs - though there is no guarantee that the ride height will not change with those. It may slightly.

Just replacing the shocks and control arms is going to make the car feel much better anyway. Save your money where you can!

christessmer420 said:

im replacing the shocks and installing tubular upper and lower control arms and spring isolators so i figured i would replace the springs as well. interesting...so ur sayin that basically unless they are broken, cut, etc. then there is no need to replace them? i was just under the assumption that, like everything else on my car, the springs were worn out. also i was told to look into getting different springs to improve handling and so on. but it seems like all aftermarket springs are lowering springs. should i just stick with the stock springs?

Click to expand...

Nope, stock springs do not wear out. The isolators DO WEAR OUT! Get new ones!

As was mentioned, Mach1 rear springs with poly isolators will lower a STOCK Fox about ~1/4" or less (5 speed, battery in stock location up front, no "extra weight" in the back from stock, etc).

Poly isolators don't compress. So, they raise a Fox approx ~1/4" (+/- ~1/4").

So, if you "must" get new/newer springs, and don't want the rear lowered, then get Mach1 springs and use poly isolators.

Also, I strongly suggest that you measure your fender height before you take anything apart. Check and set your tire pressures! It'll take a few minutes at most.

Then, do the swap. With new isolators (stock or poly) the car will sit high for a few weeks! You'll have more drop with new stock isolators since the springs dig into them more. You'll have only a little drop with poly isolators.


Long term:
In the back, with stock isolators, you'll loose a little height over the years until the bottom isolator eventually "disappear".

In the front, the upper stock isolators slowly compress over ???5-10 years???. The front lower stock isolator will also isolator eventually "disappear". And that also causes you to loose a little height over the years.


Basically, even if you put on new stock isolators and your old springs, the rear of your car will raise a little.


BTW: Since I have an '86 with fenders that aren't as wide, and I want to run 245's up front and 275's in the back, I do not want to roll my fenders (I like my stock '86 body!), and I want better handling, I also keep the approx stock height for a GT (which is already low by OEM standards!).
Mustang 86 - Mach1 Springs


Hope the above helps!

Good Luck!

If spring is loaded too much that it deforms plastically it may be lower than stock. Steel springs also are eaten by corrosion so the wire gets thinner and that way it may loose it rate a bit.

If one spring is broken it is recommended to replace both springs on same axle. One reason is that on some cars coil springs are the weak points and if one is cut soon will be the other one on same axle.

But I have seen cars with only one replaced spring and they sit as uneven as with that broken spring just on the other side. It may be caused by aftermarket stock replacement springs which not necessarily the same rate and specs as springs from production line.

It also may be cause of spring creep or relaxation which may occur in metal springs. So that is one reason to change both sides especially on older cars which our foxes now are and they are getting older. It is impossible to which kind of (ab)use our old mustangs have had so replacing springs among other suspension gearif doing restoring is not such a bad idea.