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How do I compare a Mustang front coil-over spring rate to a conventional Mustang spring in the stock location?

The spring rates must be converted into wheel rates. The wheel rate is the spring rate measured at the wheel. The conversion is done through the use of what's called the motion ratio. For a stock Fox Mustang front suspension, the wheel rate is 25% of the stock location spring's rate. For example, an 800 lb/in stock location spring has a wheel rate of 200 lb/in. For a coil-over suspension, the wheel rate is approximately 85% of the coil-over spring's rate. For example, a front coil-over spring rated at 350 lb/in would result in a wheel rate of about 300 lbs/in. Note: The exact motion ratio conversion of the wheel rate for a front coil-over suspension is determined by the angle of the strut. That angle is the result of the camber and caster settings, and by the SAI (Steering Axis Inclination).

How do I compare a Mustang rear coil-over spring rate to a conventional spring in the stock location on my solid axle equipped Mustang?

As with Mustang front spring rates, rear spring rates must be converted into wheel rates. The wheel rate for the rear of a Mustang with a solid axle and stock 4-link is approximately 50% of the stock location spring's rate. For example, a 200 lb/in stock location spring has a wheel rate of 100 lb/in. For a rear coil-over suspension, the wheel rate is approximately 110% of the coil-over spring rate (because the spring is actually behind the centerline of the Mustang's solid axle). Also, because the shocks are mounted more outboard than the stock spring location, the rolling rate of the suspension is mildly increased. This helps to reduce understeer.

How do I compare a Mustang rear coil-over spring rate to a conventional spring in the stock location on my independent rear suspension (IRS) equipped Mustang?

The wheel rate for the rear of a Mustang with IRS is approximately 28% of the spring rate in the stock location. For example, a 600 lb/in stock location spring has a wheel rate of 168 lb/in. For a coil-over suspension, the wheel rate is approximately 50% of the coil-over spring rate.

Why does a coil-over spring with a higher wheel rate ride better than a conventional spring with a lower wheel rate?

Although the front coil-over spring in the above example increases the wheel rate by over 50%, the ride quality will actually improve. A conventional spring located on the Mustang's front control arm contributes to ride harshness because of friction in the control arm bushings and ball joints. A Mustang front coil-over kit eliminates this friction by applying the spring force directly to the spindle and upper strut mount. Coil-over springs are also much lighter than a conventional Mustang spring. The resulting reduction in unsprung weight allows the suspension to more easily follow bumps in the road. Rear coil-over conversions provide a similar improvement in ride quality, although it's not as dramatic of a difference as the front kits.

What are my options for adjusting ride height?

Ride height can be easily adjusted by changing the position of the lower spring perch (The spring perch is raised or lowered by rotating it on the threaded sleeve). The 5" to 6" range of adjustment on the MM Coil-Over conversion kit is more than adequate when the correct spring is chosen for your Mustang's application.

I've been told that if I use a stiff enough spring for racing, my suspension will never bottom and I don't need bumpstops.

If you are running a spring that stiff, you will be hurting your car's ability to absorb bumps (large or small), which reduces your Mustang's overall cornering grip. To quote Carroll Smith in Engineer to Win, "If you are not USING the bump stops, you are running stiffer springs than you need and are therefore giving away some cornering power." If some type of compressible bump stop is not even installed on the car, eventually a bump will be encountered that is large enough to bottom out something else in the suspension, resulting in loss of control and damage to the vehicle.

Why does Maximum Motorsports have different kinds of Mustang front and rear coil-over kits?

The dimensions and construction features of each manufacturer's strut and shock housings are not the same. This requires subtle changes to many components.

What are the benefits of switching to a coil-over front suspension?

Better handling and better ride quality! When the spring is in the stock location on the control arm, better handling can be had with higher spring rates, but ride quality begins to suffer with rates over 650 lb/in. A coil-over kit allows the use of wheel rates that are much higher than those obtained with a 650 lb/in spring in the stock location. This will dramatically reduce body roll and brake dive. Other benefits include easily adjustable ride height, the ability to fine tune corner weights, ease of bumpsteer measurement, less weight, and a wide selection of available spring rates.

What springs are available from Maximum Motorsports?

Standard 2.5" inside diameter coil-over springs are available in 25 lb/in increments between 150 lb/in and 600 lb/in, and in several standard free lengths. The wide range of springs available means that coil-over suspension systems are easily tuned by swapping springs to balance your Mustang's handling.

Are there any disadvantages of running a coil-over suspension on my Mustang?

There may be tire and wheel clearance issues, depending on the wheel size, back spacing, and tire size. For example, our Mustang coil-over conversion kit will not interfere with a 275/40/17 tire on a 17X9 Cobra wheel on an 1987 Mustang with 1995 spindles. The Konig Villain wheels will require a 1/4" wheel spacer for clearance.

Because the upper spring perch lowers the point where the bumpstop contacts the chassis, all non-MM or non-Bilstein coil-over conversions will reduce the amount of available bump travel (no matter what others tell you). We have seen other kits that reduced the available bump travel by over one inch. To maximize bump travel, Maximum Motorsports carefully designed the upper spring perch assembly—it provides over 1/2" more travel than most other kits. Also, our exclusive bumpstop helps regain some of the lost travel because it is shorter and softer than conventional Mustang bumpstops. Don't be tempted to regain bump travel by not using bumpstops. Damage to your Mustang, caster/camber plate, or strut will occur when the suspension bottoms.

Click here for MM Front Coil-Over Conversion Kits
Click here for MM Rear Coil-Over Conversion Kits