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Linear Rate performance Springs

Article by:GTRaptor Profile | E-Mail


Stock springs suck big time, they are too soft in front and too stiff in the rear, from a "smoothness" standpoint they are ok if the car is driven in the street and if you like the 4X4 looks.

If you plan on improving the road handling of your mustang then lowering and installing better springs is a must.


INDY Springs by MRP Racing:

For the Road Racing fan, MRP Racing offers it's full line of INDY springs.

The Indy springs are great quality and MRP's special attention to road racing makes them one of the best choices around.

One important note is that with MRP recommends also using FMS or Global West lower control arms with their springs. The Indy-GW combo is one of the simplest and most effective suspension for road racing and will not cost you big bucks like other setups with pan hard rods or IRS.

MRP offers several rates for all mustang models:Y 79-PRESENT Mustang Springs Rates/Kits

FRONTS Spring Kit /Rates REARS Spring Kit /Rates

Indy-006    600lbs

Indy-061    160lbs
Indy-086    680lbs Indy-071    170lbs
Indy-008    800lbs Indy-091    190lbs
Indy-529    925lbs Indy-512    215lbs

The Spring rate you select will depend a lot on the actual use of your car, if its mostly street then a softer front and stiffer rear is desirable but wont be the best for road racing. 700/170 springs are recommended by MRP for street use, while the 800 or 925 fronts with 160s in the rear.




Place car on jack stands, the car should be lifted from the frame so that the axle is free to hang down. Remove the rear wheels, the quad shock bolts on the axle side and the pinion snubber. (discard)

Place another jack on the rear axle differential housing and raise it. Now remove the axle side shock bolts and nuts. Loosen the upper arms differential side bolts and remove, this will allow the differential to drop completely and makes it easier to remove the springs.

Lower the jack at the differential and remove the springs. Be careful not to lower the rear too much or you can break the rear brake line that sits at top of the differential case.

NOTE: Remove the lower arm-to-axle pivot bolt and nut if the springs wont come out or use a spring compressor.

Put the springs back in place. Now raise the differential to align the lower arms to the axle mounting points.


FRONT SPRINGS: (pics soon)

This is the tough part, you will most probably need a spring compressor so go buy or rent one. On our project car we had EIBACH 1.5 lowering springs so removing them was done without a spring compressor.

Raise the front on jack stands.

If using a compressor place a jack under the Lower arm and raise it, now compress the springs to get them out.

If you don't have a compressor place a jack under the Lower arm. Remove the wheels and lower the jack under the lower arm, now remove the  sway bar links and front struts. The steering tie Rod ends should also be removed from the spindle to make the job easier. You might have to use a crow bar to remove the spring. At this point BE VERY CAREFULL, make sure the spring is FULLY EXTENDED, if not it could jump out of the perch and hit you....and trust us IT WILL HURT.

Reverse for install.

Final Comments

The car was lowered 1" with the Indy Springs, so it is taller than with the 1.5 Eibach's and our final combination consists now of Global West LCA's and Indy Springs, shocks and struts are still stock. This is not the best combination because the rear is a bit too soft for the stock shocks, but trust us, its a lot better than stock. A complete setup should include either KONI DAs or at least Tokicos adjustable's or Bilsteins.

Now about the ride, the front is STIFF, but it doesn't feel that bad with the 700 rate linear springs, the rear feels softer but its not bouncy, here the Global West arms contribute to the rear end stability.

Our first road tests show that the car is a lot more predictable, and on uneven roads the front wont bounce as with the Eibachs, the rear end hooks great with no fishtailing or over steer. The car in general is pretty much neutral,   when with the Eibachs it was a bit unpredictable, it over steered or under steered depending on road conditions.

The setup is far from perfect yet, adjustable struts/shocks   should go next, and will also need front arm bushings and CC plates to get the correct caster/camber/toe settings.


If you plan on improving the road handling of your Mustang then lowering and installing better springs is a must.

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