Weight Myths: Fox Mustang K-member and Front Suspension
There are lots of numbers floating around about how much weight you can save when installing an aftermarket K-member, front control arms, and coil-over kit on the front of a Mustang. Although we've long heard the oft-cited, greatly exaggerated range of "between 75 and 100 lb," no one has ever published an accurate analysis of the achievable weight reduction.
Until now.
Below is a list of the stock Ford parts that are replaced with the typical aftermarket K-member installation in a Fox chassis Mustang. There are small differences in the weight of some of the stock parts, depending upon the year of the car. In this example, all of the parts listed are from a 1990 Mustang LX 5.0.
| Stock 1990 Parts |
Weight (lb) |
| K-member |
48.5 |
| Front control arms |
13.5 each |
| Coil springs |
12.0 each |
| Front spring isolators (all 3 pieces) |
1.1 per side |
| Upper strut mounts |
3.5 per side |
| Steering rack bushings |
0.414 per side |
| Outer tie rod-ends |
1.27 each |
| Total |
112.1 |
Below is a list of the MM parts installed as part of a Fox chassis K-member installation.
| MM Parts for Fox Chassis |
Weight (lb) |
| MM K-member |
37.0 |
| MM Tubular Front Control Arms |
8.0 each |
| Hypercoil 2.5" springs (14" x 200lbs/in) |
4.5 each |
| MM Caster Camber Plates |
3.0 per side |
| MM Coil-over Kit (for Koni) |
1.0 per side |
| MM Steering Rack Bushings |
0.187 per side |
| MM Outer Tie-Rod End Bumpsteer Kit |
1.47 each |
| Total |
73.3 |
This particular combination of MM parts for a Fox chassis Mustang provides a weight reduction of 38.8 lb.
What about the weights for an SN95 Mustang?
While the weights of the individual parts do vary slightly, the differences are quite small, with the overall weight reduction being just a very few pounds shy of this Fox example.
Could more weight be removed?
Sure, there are companies that make lighter-weight K-members, dropping as much as an additional 18 lb. The potential weight reduction of 57 lb is still a far cry short of the often claimed 75-100 lb reduction.
But...
Keep in mind that the K-member is a mission-critical part that:
- Provides the load path into the chassis for forces from the front suspension, and it should do so without flexing. When the K-member flexes it affects ride quality, handling, braking, and long-term durability.
- Supports the weight of the engine.
- Resists the reaction to the engine's torque output.
There are reasons why Ford didn't make the stock K-member lighter; it weighs what it does because it provides optimum strength and durability. The same goes for MM K-members. We designed each to last the life of your car, while providing you with improved performance for the entire time.
MM K-members for Mustangs