On My 65 restomod convert I have 1 inch lower coils in front and 4 leaf 665lb ( Suppose to be) leafs and racing shackles in rear.
Car seems to sit a bit low in rear. What performance leaf springs do you run and how can I tell if mine are shot.
Thanks :
Tom

 

I think you just said it. If you have the original leaf springs, they are sagging because of age. Replace them with three variations of new leaf springs. Standard eye will give you the factory set-up, mid-eye will lower the rear about an inch, and the reverse eye will raise it about an inch. The 4 leaves will give you factory height, the 4 1/2 will give you a somewhat stiffer ride, and the 5 leaves are for godawful horsepower to the rear and will be very stiff . Other factors come into play here though. What shock absorbers are you running, and do you have any other rear suspension upgrades?

 

Stock the Mustangs appear to sit slightly low in the rear. IIRC for '65 & '66 with stock height tires (approximately 25.5") the height to the top of the fender is supposed to be 26.5" front and rear. It's been a long time since I've looked this up (it's in the factory manual IIRC).

I'm still running stock springs, but with stiffer shocks (convertibles need a little more compliance). Really hard to tell spring sag on aftermarket springs, unless you measured fender lip height after break-in when new. Normally one side will sag more than the other slightly (like 1/4"-1/2").
You should see an arch, the size of which varies with the type of spring, but somewhere between 2" and 4". That's a lot of variance for sag, sorry I can't be more precise for you.

Maybe someone else with the same spring will chime in here.

Good luck,

 

Well, after replacing my 40 year old springs, I immediately noticed a difference in ride height, even though I replaced them with 4 leaf aftermarket leaves.