Holy cow... No, when installing lowering springs on a coilover/McPherson strut car like the Mustang you
DO need a spring compressor. Very much so! A typical S197 front spring makes about 100-110 pounds of force per inch of compression, and the stock spring is compressed about 4", even at full droop... so there are 400+ pounds of force ready to come loose when you zing off the strut top nut.
Here are some step-by-step pictures below that show the process of installing a lowering spring on an S197:
http://vorshlag.smugmug.com/Instruct...camber-plates/
Granted, that is a camber plate install gallery, but most of the steps apply to doing a lowering spring install. You still have to remove the strut assembly from the car, compress the spring, remove the strut top mount and upper perch, swap the spring, and reinstall in the reverse order.
Of course, if you are going to all of that effort to swap the springs, it is zero extra effort to swap in some Vorshlag camber plates, hehe.
But if you have no intentions of ever doing any autocross, track driving or canyon carving, then you don't "need" more negative camber or positive caster adjustment.
One thing that always trips people up when they slap on lowering springs: if you keep the same OEM length struts, the amount that you are lowering the car with the new springs is the same amount that you will lose in suspension bump travel.
So, let's say you have 2" of bump travel stock, and you lower the car 1.5"... how much will the suspension have to move under compression before you are slamming into the bump stops? Answer = 1/2".
THAT is why most "lowered car" ride so poorly - the struts are not shortened to accommodate this loss of bump travel. But who is going to make shorter than stock struts that are made for an OEM spring? (answer - one company, shown below) For a properly designed coilover strut made to run at lower ride heights we always shorten the strut body considerably, to compensate. This will lose "total suspension stroke" but often gain inches of bump travel over the standard "lowering spring on stock struts" kind of install.
But good coilvoers cost from $2500-3000 and up for these cars (and by
good I mean "Not Chinese", not KW, and not twin tubes). So we came up with an alternative for lowering Mustangs without busting the bank... a Bilstein inverted monotube strut that is 1.25" shorter than stock length S197 struts. We couple these with our camber plates and several lowering spring choices, build it all into a strut assembly ready to install, then sell it for
$1499. It is very popular because... it gains back that 1.25" in compression travel when lowered. And you don't re-use anything from the old strut/spring/upper mount assembly, so the install takes half the time and you don't need a spring compressor.
Not trying to sell you on something, more of a warning of what will likely happen when you lower the car using the same stock length struts. This issue happens with OEM, Konis, Tokicos, and just about anything else made to use the OEM style springs,
other than the Bilstein monotube shown above.
If the ride doesn't matter to you, and crashing around on the bump stops is not a worry, then feel free to ignore all of this. We tend to hear from customers who have already "Been there, done that" with the lower spring only solutions and are finally looking for better ride quality, more performance, AND the lowered ride height. It can be done if you know what to get...
Cheers,