Installation Instructions For Mustang II Suspension Kits

This set of instructions have been put together so the average guy should be able to put an updated suspension kit on their hot rod or street rod project. You do not need to understand, or have a degree in front end geometry to be able to successfully install the hub to hub Mustang 2 Suspension kit. Updating your project to 11″ cross drilled and slotted disc brake rotors, and rack and pinion steering for improved handling and performance can be accomplished if you have basic welding skills, can read a tape measure, and use a level.

Here is a list of the things you will need for a successful installation of your Mustang II Suspension Kit

  • 1.  Level work area.

Working off of a level surface is a must with these instructions. The floor must be level from side to side, a level surface from front to back is best but not required.

  • 2. A Tape Measure

A 20′ tape that measures to a 1/16″ is ideal.

  • 3. Levels

A 4′ level and a 6″ magnetic level work best.

  • 4. A Welder 

I use a MIG (wire feed) to tack everything in place, but a TIG or a stick welder will also work.

  • 5. a Square 

A quick square works well but a carpenters square is sufficient if that’s all you have.

  • A Scribe and a Permanent Marker or Soap Stone

These are used for marking reference points.

  • A Hand Held 90 degree Grinder and a Cut off wheel 
  • A set up Wheel and Tire inflated to the pressure it will be run at

This needs to be one that you will be using on the finished project and will need to be inflated to the pressure that it will be run at on the vehicle.

In most cases the best place to start is the beginning. Using these instructions you will be starting from the end.

Let’s get started.

Positioning Your Project 

The first thing you will need to do is place the Vehicle into a level side to side work area. If working off a concrete slab, place a 4′ level on the floor at the vertical spindle center and make sure the floor is level from side to side. If it’s not, use a piece of sheet steel or 1/2″ plywood to level the floor. Once the floor is level position the project at the exact ride height and posture or rake that you want the finished project to be. This is the desired ride height and posture that you want the finished project to be when it’s all put together and driving down the road. 

Establishing The Vertical Spindle Center Line 

The factory vertical spindle line should be scored on the frame rail BEFORE the original suspension is removed. In some applications, like a ’53 to ’56 Ford F 100, it is desirable to move the vertical spindle center point forward 3/4 of an inch or so to better center the wheel and tire in the wheel well.

If the  factory suspension has been removed prior to set up, you can simply use the set up wheel and tire to find where it is best centered in the wheel well opening and then mark the center of the wheel and tire on the frame rail.

It is imperative that the vertical spindle center line be located in the same place on both sides of the vehicle so a reference point on the frame rail that is consistent on both sides should be used to measure and make sure that both sides are in exactly the same place.

 While the upper spring towers are centered on the vertical spindle center line the cross member is not.

Once the vehicle is loaded into the work area, and the vertical spindle center line is established on both frame rails, you’ll need to put a level across the frame rails at the spindle center line to verify that the frame rails are level.

The first component of the kit to be installed is the center section of the cross member. If your vehicles frame is an open C channel, the frame rails will need to be boxed off  before the cross member can be installed.

Boxing plates for specific applications such as  1964 to 1970 Mustang and 1948 to 1956 Ford trucks are available. If the frame rail is at a constant height, then flat plate steel of the same gauge as the frame rail may be used . The frame will need to be boxed for a distance of 18″ centered on the vertical spindle center line to install the cross member. Some people like to box the frame from the firewall to the front of the frame, I personally like to box the frame from front to back .

  The cross member in this kit will need to be notched to establish both desired ride height and to fit between the inside of the boxed off frame rails. Before we discuss how to determine where the notches in the cross member will be located, we need to discuss the spindles.

Previously we established the vertical spindle center point and scored it’s location on the frame rail. Now we need to establish the horizontal spindle center point. To do this the following formula works well.

Stand the set up wheel and tire on it’s tread surface as if it were on the vehicle. Measure from the ground up to the highest point of the tread surface. This is the inflated tire diameter. I will use 28″ as an example, but you will need to use your inflated tire diameter  in the formula to develop your horizontal spindle center.

We need to divide the inflated tire diameter by 2 and subtract 1/4″  for the flattening of the tire under the weight of the vehicle. So 28″ divided by 2 = 14″  – 1/4″ =  13 3/4″ By the example 13 3/4″ is the horizontal spindle center point. This is where the horizontal center of the spindle will be located with a 28″ tire no matter what your ride height is set at.

2″ Drop Spindle Vs. Stock Ride Height

On the initial installation a 2″ drop spindle does not change the ride height. You are choosing your ride height on the initial set up of the vehicle. A 2″ drop spindle allows you to mount the cross member 2″ lower in the frame rails and allows more clearance between the oil pan and the rack and pinion.  The Mustang II  suspension kit is designed to lower the vehicle at least 2″ and can lower the vehicle up to 6″ with a stock ride height or a 2″ drop spindle. Since the vehicle is set up at your desired ride height, you can determine whether you need a stock ride height or an optional 2″ drop spindle like this :

Measure from the ground to the side of the frame rail @ the vertical spindle center point 13 3/4″ (By our example) and place a mark on the frame. If this mark comes out below the frame rail it’s ok, this is a common occurrence and will depend on where your ride height is set at.

 If it comes out more than 2″ below the frame rail, you should rethink your ride height.  If the horizontal spindle center point comes out in the lower 50% of the frame or below, a stock ride height spindle will be best for your project. If it falls in the top 50% or above the frame rail, you will be better off with a 2″ drop spindle for your project. Some applications like a 1964 to 1970 Mustang require a drop spindle for added Engine clearance.

 Using a stock ride height spindle, the lower control arm mounting hole will be located 3 1/2″ below the horizontal spindle center when the cross member is installed and tacked into place.

With a 2″ drop spindle the center of the lower control arm mounting hole is 5 1/2″ below the horizontal spindle center point.

Our example uses a 28″ tall tire so our horizontal spindle center is @ 13 3/4″. For our example we’ll say that  13 3/4″ measured from the floor comes to 1″ above the bottom of the frame so we will use a stock ride height spindle. If we subtract 3 1/2″ from 13 3/4″  that would place the center of the lower control arm mounting hole @ 10 1/4″ off of the ground when the cross member is installed.

The cross member needs to be located so that it is level front to back as well as side to side , so the lower control arm mounting holes will be 10 1/4″ from the ground at all four points when the cross member is tacked into place.

Marking the Reference Points

 

This is a good time to mark the 4 reference points on the frame rails where the side walls of the cross member will be located. The cross member with this kit is 3 1/8″ wide from outside to outside of the front and back walls and is off set so you will need to  measure (1″) forward of (towards the radiator) and (2 1/8″) behind (towards the firewall) of the vertical spindle center point to center the cross member. Mark the 4 reference points all the way around the boxed off frame rail. These are the points where the front and back walls of the cross member will be located.

When figuring where the notches will be placed in the cross member, you should keep in mind that the notches in the front side of the cross member and the notches in the back side will almost always be different so you need to do the math on all four points.

We know that the center of the lower control arm mounting holes will be 10 1/4″ (by our example) from the ground (at all 4 points) when the cross member is in place, so we need to measure the distance from the bottom of the frame to the ground at all 4 of the reference points one at a time. It’s important to do the math at all four points to compensate for any inconsistencies in the frame rail and to avoid the possibility of welding a gap. You want a good tight fit with the cross member and it must be level front to back and side to side.

I’ll start with the driver’s side reference point that is forward (towards the radiator) of the vertical spindle center point.  For our example lets say that from the bottom of the frame rail to the ground is 12 1/4″ .

 If we subtract the distance of the lower control arm mounting hole to the ground 10 1/4″ from the distance of the bottom of the frame to the ground 12 1/4″ that gives us a difference of  2″.

We would then measure on the left front corner of the cross member from the center of the lower control arm mounting hole up the side wall 2″ and place a mark. This is the location of the horizontal notch in the cross member.

Next we’ll measure for the drivers side rear. I like an inch or two of rake on my projects so the drivers side reference point behind the vertical spindle center from the bottom of the frame to the ground we will say is 12 1/2″.

If we subtract 10 1/4″ from 12 1/2″ we have a difference of 2 1/4″.

  Measure from the center of the lower control arm mounting hole on the back side of the cross member up the side wall 2 1/4″ and place the mark. this needs to be done at all four points for the cross member to fit tight and come out level.

We now have a horizontal notch marked on all four corners of the cross member so we need to figure out where the vertical cuts will be. It is important that the Cross member is centered between the frame rails. Frame rails almost never run parallel so once again the front and back vertical cuts will almost always be different.

Measure the over all width of your cross member. The one for our example is 31 1/4″

Measure the inside to inside of the frame rails at the reference points forward of the vertical spindle point. For our example we have a measurement of  25 3/4″.

Here’s the formula : 31 1/4″ – 25 3/4″ = 5 1/2″ now divide 5 1/2″ by 2 = 2 3/4″

Measure  from the outside edges of the cross member in toward the center 2 3/4″ on both sides of the front of the cross member  and place  marks. These are the locations of the vertical notches on the front side of the cross member. Repeat this procedure using the reference points for the back side vertical cuts.

Now you should have a vertical and horizontal cut marked on all four corners of the cross member. Simply lay your square on these marks and draw a line around it. This marks the notch that will be cut out. Once the notches are cut out test fit the cross member into the frame rails. Tack it into position when you have verified that you have a tight fit and a measurement of 10 1/4″ from the center of the lower control arm mounting holes to the ground at all four points. You can massage the notches with the grinder if necessary to achieve perfect placement of the cross member.

Placement of the Spring Towers

The spring tower will be placed so that a straight up vertical measurement from the center of the lower control arm mounting hole to the surface that the upper control arm bolts to on the spring tower  is 9 1/4″ on the front side of the cross member. This measurement is 8 7/8″ on the back side of the cross member.

This is a built in 3 degrees of positive caster or an anti – dive angle. If we add these measurements to the center of the lower control arm to the ground measurement of (10 1/4″) we will have the measurement that we need for the top of the spring tower (the surface that the upper control arm bolts to) to the ground. For the front side we will add 10 1/4″ + 9 1/4″ = 19 1/2″.

 Take one of the spring towers to the drivers side frame rail. You will be building in the anti – dive angle so mark it with a L to avoid confusion later. Place the spring tower up against the outside of the frame rail and center it  on the cross member. Move it up or down until you achieve the measurement of 19 1/2″ from the top of the spring tower to the ground. Use a straight edge on the top of the frame rail to mark the horizontal cut on the front side of the spring tower.

The back side of the spring tower is 3/8″ lower so mark the top of the frame rail location onto the spring tower on the back side at 19  1/8″ from the ground.

Please remember that these measurements are for a 28″ tall tire and a stock ride height spindle. If you’re using a different size tire or a 2″ drop spindle your measurements will be different. so use these as an example and do the calculations with your measurements.

The next step is to install the lower control arm. The front side of the lower control arm runs almost parallel with the cross member while the back side of the control arm angles toward the rear of the vehicle. When the control arm is installed you will want to block it up so that it is straight out and level with the ground. Next install the spindle on to the lower control arm. Bring the spindle up to zero camber pointing straight out side ways. This can be precisely accomplished by attaching a magnetic level to the brake caliper bolt holes.

 Bolt the upper control arm to the spring tower in the middle of the adjustment slots. Place the spring tower on top of the frame rail centered on the cross member walls. Hold the upper control arm straight out level with the ground and the upper ball joint pointing straight down. Move the spring tower in toward the engine bay or out towards the tire until the ball joint lines up with the hole in the spindle. Make certain that the spring tower is centered on the vertical spindle center point and square with the cross member (not the frame rail)  Using a straight edge mark the outside of the frame rail position onto the spring tower walls on the front and back sides. Repeat this procedure with the right side spring tower except mark it with an R.

You will now have a horizontal mark and a vertical mark on each side of both spring towers. Lay your square on the two marks , draw a line around it, this is the notch you will need to  cut out. This method will put you at zero camber in the middle of the adjustment.

Once the notches have been cut out, place the spring towers on the frame rails and using the level verify that they are at the same height.

The surface of the spring tower that the upper control arm bolts to will be at a down hill angle towards the fire wall.

Mounting the Rack and Pinion 

The proper placement of the Rack and Pinion brackets on the cross member is important to avoid the possibility of Bump Steer. The steering arms on the rack need to run parallel to the lower control arm when it is installed and parallel to the ground.

To do this bolt the rack brackets onto the rack and pinion with the spacers in between the two. The spacer is there to provide clearance between the tie rod end and the lower control arm Install the tie rod ends onto the steering arms  on the rack. Install the tie rod ends up through the steering arms on the spindles.

On the front side of the cross member you will find reference lines scored into place to center the rack from side to side. Line the rack brackets up with these lines and place the rack up against the front of the cross member. Raise or lower it until it is a at point where the steering arms on the rack are parallel with the lower control arms and the ground.

In cases where you have chosen an extremely low ride height, it may to be necessary to C – notch the bottom of the frame rail for additional steering arm clearance.

It is important that the rack and pinion steering arms do not run down hill or up hill to the spindle. Once the proper location is found, either mark the position of the rack brackets or tack them into place. You can now remove them from the rack assembly and weld them down to the cross member without the risk of damaging the bushings.

Set your initial alignment specifications and confirm your final geometry. If everything is good to go you can weld it all down solid and do a final assembly.