Leaf Springs

Leaf springs are a type of suspension spring made from multiple curved steel leaves stacked on top of each other, clamped together at the center, and attached to the chassis at both ends.

How they work:

• Main leaf (longest) attaches to chassis via shackles

• Additional leaves stack underneath main leaf

• Leaves slide against each other when compressed

• Spring rate determined by number, thickness, and arch of leaves

• Support vehicle weight and absorb road impacts

Classic Mustang rear suspension:

• Two leaf springs (one per side)

• Typically 5-leaf springs from factory

• Front mount is fixed (bushing in frame)

• Rear mount is shackle (allows length change)

• Rear axle attaches to center of spring via U-bolts

What leaf springs do:

• Support rear of car

• Locate rear axle (keep it centered)

• Absorb bumps and impacts

• Provide suspension travel

What they don't do:

• Stay at factory height forever (they sag)

• Provide good handling (compared to coilovers)

• Resist body roll effectively (that's sway bars)

• Look cool (except on Bullitt Mustangs, maybe)

I drove my Mustang for 2 years with sagged rear springs. The car sat 2 inches lower in back than front, creating that "late '70s muscle car" rake. I thought it looked period-correct. My wife said it looked broken. She was right. New springs brought it level and made the ride significantly better.

Leaf springs sag with age, affecting appearance and handling:

Original 50-year-old springs:

• Sagged 1-3 inches below factory height

• Weak spring rate (soft, wallowy ride)

• Reduced suspension travel

• Poor handling (excessive body roll)

• "Tail-dragging" appearance

• Cost to fix: $300-$1,500

New replacement springs:

• Factory ride height restored

• Proper spring rate

• Full suspension travel

• Better handling

• Level stance

• Cost: $300-$800 (parts + install)

Upgraded performance springs:

• Factory height or slight lowering (1")

• Stiffer spring rate (less body roll)

• Improved handling

• Modern materials (won't sag)

• Cost: $500-$1,500 (parts + install)

The ride height reality:

Your Mustang should sit level or with a very slight rake (front slightly lower). If the rear is 1+ inches lower than front, your springs are sagged and due for replacement.