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Good Handling Is Fun: How Low Can You Go?

Topic #4 from the "Good Handling Is Fun" series of MM newsletters.

Welcome to the fourth installment of our weekly series of Good Handling Is Fun newsletters. Our goal with this series is to present you with information to help you modify your Mustang to have more fun with it; i.e., to help you transform your Mustang into a high-performance handling machine. If you missed any of the previous episodes, they're posted on the MM website in the FAQs & Tech Tips section. This week's topic is all about lowering your Mustang.

Most people agree that a lowered Mustang looks better and more aggressive than one at stock ride height. Whether your taste runs to really getting it down in the weeds or you like your ride just a little lower than a stock 4x4, lowering is a common practice.

Besides looks, are there any benefits of lowering?
Oh, yeah. Lowering the center of gravity, with all else remaining equal, will increase your Mustang's potential cornering speed. Major win there, but lowering also increases the deceleration level you can get while braking, shortening stopping distances.

Maximum cornering speed is a function of center of gravity height, track width, corner radius, and tires' coefficient of friction on the road surface. In other words, lower, wider, and stickier all result in higher possible cornering speed. But, as with most terrific things, there are trade-offs.

What are the drawbacks of lowering?
  • The obvious one is less ground clearance. You might scrape things off the bottom of your Mustang when encountering annoying speed bumps. The bottom of the car's front fascia might scrape when entering or leaving a driveway, making you and nearby pedestrians wince and question your driving ability.
  • This one's kind of big: it's not obvious, but the suspension geometry will change, and that's not easily correctable. Take it from us, these changes won't be for the better. A lower center of gravity height reduces weight transfer to the rear tires, which reduces grip for that glorious acceleration. At the front, the roll center will lower significantly, which leads to bad handling. In other words, if you don't do it right, lowering too far makes a mess and pretty much ruins your Mustang's handling.
  • The front alignment will change, which may cause poor handling and will definitely reduce tire life. But you can easily correct this with a good alignment. Aftermarket parts such as MM's Caster Camber Plates are often required to align a lowered Mustang to Ford's camber specification, which is good for street cruising. IRS-equipped Mustangs will need a rear alignment, as well.
  • Ride quality often suffers. Lowering a car reduces the amount of bump travel available in the suspension, which increases how often the car bottoms out on the bumpstops. Higher-rate springs reduce the frequency of bottoming, but they also cause firmer ride quality. When a car is lowered, some increase in spring rate is pretty much required to keep the suspension from hitting the bumpstops too often.

How bad are all these things?
Well, unless you do it properly, the lower the car gets the worse your handling problems will be. With a moderate amount of lowering you might not notice the impaired handling during regular street driving. But as cornering speed increases and approaches the tires' grip limit, like if you go autocrossing or out on a weekend road course, you'll get frustrated with ever-increasing lap times. Ever wonder why that seemingly identical Mustang is so much faster than you? They've probably addressed the geometry issues that come with lowering.

What can be done to correct the geometry?
Glad you asked! In the front:
Change the geometry by moving the suspension pivot points to a location more suitable for the lowered ride height. MM K-members do this by relocating the front control arm mounting points upward. That moves the front roll center back up to a much better location for handling. Then install an MM Bumpsteer Kit to address the revised K-member geometry.

In the rear:
Change the geometry by moving the suspension pivot points to a more suitable location with rear lower control arm relocation brackets, or add an MM Torque-arm to stabilize the instant center (IC) location for better traction. FYI: the IC location is integral to determining the anti-squat geometry, which directly affects traction.

What about the bumpsteer problem?
You might have noticed we didn't bring this up yet. That's because—despite the widespread myth, which predates the Internet—lowering a late-model Mustang doesn't cause a significant increase in the amount of bumpsteer (toe change with suspension movement), provided the car's alignment is returned to its original settings after lowering. All lowering does is move the car to a different point along the existing bumpsteer curve. If the existing curve was very flat, moving the starting position to a new point along the same line doesn't appreciably change anything.

How do you know this?
We here at MM are kind of obsessive measurers. Bumpsteer can be measured, just as the camber and toe setting are measurable. We've done tests, measuring before and after lowering. Those spreading the bumpsteer myth have obviously never done much measuring! Bumpsteer can also be modeled with the help of a computer. Of course, we do this when designing our suspension products. Don't worry, we'll devote an entire future edition of this Good Handling Is Fun series to bumpsteer. Stay tuned!

Enough theory; what are the nuts and bolts of lowering?
In a nutshell, lowering a Mustang without ruining its handling involves these parts:
  • Springs; choose from many offerings.
  • Spring isolators; required primarily for 1979-2004 Mustangs.
  • Caster camber plates; usually required to realign the front end.
  • Dampers; aftermarket springs are usually higher rate than stock springs, and therefore require upgraded struts and shocks to maintain ride quality and performance.
  • Bumpstops and pinion snubbers; some Mustang models can use shorter bumpstops and/or pinion snubbers to regain some of the bump travel lost from lowering.

There are many spring choices available for lowering and performance. Maximum Motorsports carries the top brands: Eibach, H&R, and our own custom MM Springs. Different springs offer different amounts of lowering and spring rates. Some springs are best suited for lowering and others for improved performance.

1979-2004 Mustangs have a notoriously confusing array of springs available. Check out our handy Guide to Choosing Spring Rates and Dampers for help, or we can make a recommendation for your Mustang based on how you'll use your car. 2015-current Mustangs have fewer choices, making it easier to decide on which spring set will work best for you.

Spring Isolators
These are the rubber pads located at each end of OEM springs. Ford put them in to reduce NVH, which may not annoy you, but will likely aggravate any passengers of the non-driving enthusiast variety. Spring isolators are also an important factor affecting ride height because of their location between the end of the spring and the spring perch. The original isolators on 1979-2004 Mustangs are not very durable. By now they are falling apart before your very eyes, perhaps even to the point of disintegrating and disappearing. If your 1979-2004 Mustang still has its original OEM spring isolators, the chassis is probably already lower just because they're collapsed or altogether absent. Whenever installing new springs, the isolators should be replaced with aftermarket urethane isolators. Please note: All spring manufacturers assume your Mustang has new isolators installed when they list the amount of lowering for a spring set. 2005-current Mustangs have very robust OEM isolators, so no replacements needed for those.

Caster Camber Plates
As we said before, after installing new springs your Mustang will need to have a front end alignment done. Why? Let's review: any change in ride height will cause the camber setting to change. Any camber change will, in turn, cause the toe setting to change. Hence, your car needs an alignment to get everything back in spec and avoid excessive tire wear. It's like that old song, "the hip bone's connected to the leg bone...."

The required amount of camber change for a lowered Mustang to be in spec is usually greater than the range allowed by the OEM camber adjustment. 1979-2004 Mustangs have a limited adjustment range in stock form, but stock 2005-current Mustangs do not have any provision for adjustment.

Enter the legendary MM Caster Camber Plates! These provide all the camber adjustment range you need, and also allow caster adjustment. Voila! MM Caster Camber Plates let you go beyond a simple factory-spec alignment, allowing adjustment to settings that also boost performance.

Dampers are the struts and shocks, which cancel out uncontrolled spring oscillations. OEM dampers are designed to control the OEM springs. Aftermarket springs are stiffer than most stock Mustang springs. (Exceptions include some special Mustang models that Ford equipped with higher-rate springs for better handling). Higher-rate springs require stiffer damper valving to control them. Reusing stock dampers with stiffer aftermarket springs usually causes poor ride quality and reduced handling abilities. Listen to the Voice of Experience: if you're already going to all that trouble, live a little and upgrade your dampers, or the results will be lackluster at best!

MM carries high-quality dampers from several sources. Our popular Guide to Choosing Spring Rates and Dampers will help you decide, or contact an MM Tech Associate for advice. We'll recommend dampers to match the springs on your Mustang and your goals for the car, whether you want a street cruiser or better handling, or both.

MM Caster Camber plates for 1979-2004 Mustangs include new bumpstops for maximum possible bump travel. The combination restores some of the bump travel lost when the car was lowered. The bump travel of the rear suspension on these cars is limited by the axle tube hitting the frame rail, so there's not much that can be done in the back to restore bump travel. 1979-1993 models have very stiff bumpstops mounted on the frame rails. Installing 1994-2004 solid-axle shocks in the 1979-1993 cars lets you remove the frame rail-mounted bumpstops and use the superior progressive bumpstops that were OEM equipment on the later-model shocks.

2005-2014 Mustangs can be retrofitted with shorter bumpstops when you install stiffer lowering springs. This significantly improves ride quality, especially at the rear.

Pinion snubber
1986-2004 solid-axle Mustangs with the 8.8" rear axle have a pinion snubber mounted to the trunk floor, right above the nose of the differential, to help control wheel hop. On a lowered car, this pinion snubber limits the rear suspension bump travel almost the same way a bumpstop does. In 1997, we designed a shorter, progressive pinion snubber that really improves ride quality after lowering by reducing the impact from bottoming out the suspension.

And there you have it!
Now, armed with this knowledge, go forth and lower your Mustang! Just make sure you address the consequences for your particular car. A street cruiser may be just fine with only an alignment afterward, but for best handling and ride quality, go the extra mile and do it right. Trust us—you'll be glad you did!

These weekly newsletters are posted on the MM website in the FAQs & Tech Tips section in case you missed a previous episode, want to read them again, or forward to a friend. Stay tuned for next week's exciting, springtime topic, "Put a Spring in Your Step!"