spring spacers

Shown above are the stock rubber spring isolators, some 1" aluminum isolators, and two different 1/4" urethane isolators (the stock Hotchkis and an aftermarket).

Before getting into the specific spacers available, it is worthwhile to take a look at the front suspension geometry.

control arm leverage:

To calculate the expected change in ride height you need to account for the leverage factor of the control arms.  The leverage amplifies the change in ride height.


According to my measurements, the total arm length (L2) from the centerline of the chassis pivots to the centerline of the lower ball joint is 18.5".  The distance from the center of the spring pocket to the chassis pivots (L1) is 11".  This results in a 1.68:1 leverage factor.

So adding a 1" spacer will actually raise the front ride height by about 1.7".

available spacers:

Jegs carries Energy universal urethane spring isolators, which look like they will fit fine:

3/8" isolators (part # 355-9-6101):

Outside Diameter (A): 5-7/16''

Inside Diameter (B): 3-3/4''

Lip Outside Diameter (C): 4-1/16''

Lip Height (D): 1/2''

Pad Height (E): 3/8''

Total Height (F): 7/8''

5/8" isolators (part # 355-9-6120):

Outside Diameter (A): 5-7/16''

Inside Diameter (B): 3-3/4''

Lip Outside Diameter (C): 4-1/16''

Lip Height (D): 1/2''

Pad Height (E): 5/8''

Total Height (F): 1-1/8''


They can probably be stacked with a little trimming.
Energy also makes some F150-specific "1" lift" coil spacers (part # 355-4-6106).  $50 at Jegs.  I don't know whether that's 1" at the coil or 1" at the wheels.

Prothane makes some "1.5" lift" spacers (part # 6-1707).  I bought a set and they look great.  They are 1.9" tall, and the spring sits 1" in the pocket, so it's a net of about 1" lift.  Combined with the geometry of the LCAs, that probably works out to about 1.5"

[photo to come]

The 1" aluminum spacer shown above is apparently manufactured by Specialty Products Company (1-800-525-6505).

Part #s:

1703: .5" thick

1704: .625"

1705: .750"

1706: 1"


Afco makes some trick trim-to-fit spacers for about $22 apiece (part # 20192).



Ruslow 1,100 lb springs are 11 3/4" long and have 5.5 active coils 13/16" diameter.  The OD is 5 1/2" and the ID is 3 7/8".  According to this spring rate calculator, it is just about spot on 1,100 lbs/in (1,109).

In combination with a 1/4" urethane spring pad, the spring stack shown above measures 13 1/8" tall.

The stock springs are 13 3/4 long and have 7 active coils 3/4" in diameter.  The OD is also 5 1/2".  That calculates to 606 lbs/in.

Trimming one coil from the stock springs raises the spring rate to 707 lbs/in.  Trimming a coil and a half yields a spring rate of 772 lbs/in.


11/06/2006 Tim Skelton