Steve Baur
Former Editor, Modified Mustangs & Fords
September 24, 2014

As we have found more and more ways to increase horsepower in our late-model Mustangs, aftermarket suspension components have become an important part of the Mustang performance equation—so much so that the NMRA has now allowed the use of tubular suspension components in it's entry-level class, Factory Stock. Improved power output pushes the factory suspension beyond its intended design limits, and this can result in reduced on-track performance, component failure, and worse. In this article we upgrade the suspension components on a modified 2004 Mustang GT to bring that vehicle system in line with its aftermarket engine modifications, and to improve on-track and on-street performance.

UPR Products of Lake Worth, Florida, has been manufacturing upgrade parts for late-model Mustangs for years. When we came across a New-Edge Mustang looking to improve its 60-foot dragstrip times, we called UPR to see what we needed.

To improve weight transfer on launch, we went with UPR's mild steel tubular front K-member (the company also offers a chromoly version) and control arms. UPR says the kit drops 64 pounds off the front of your Mustang, a significant amount of weight. This reduction in mass will not only aid weight transfer on the dragstrip but will also improve the overall balance of the car and change the innate oversteer/understeer dynamics.

There’s no better way to improve weight transfer to the rear of the car than taking weight off of the front, and the easiest way to accomplish that is by swapping the stock K-member and front control arms with tubular versions such as 2005-96SK kit from UPR. This is a mild-steel version that fits ’96-’04 Mustangs and retails for $599.99. It’s constructed from seamless tubing and TIG-welded in a billet fixture for accuracy. UPR designed this for the abuse your ride may receive at the track, as well as many miles of street driving.

At the rear of the vehicle we went with UPR's Pro Series Chromoly Rear Suspension Kit. The package includes adjustable upper and lower control arms featuring spherical bushings for optimum control and precise adjustment. Also included with this rear suspension kit is a drag-race-specific antiroll bar. UPR offers a standard antiroll bar, one with the links moved inward for improved exhaust clearance, one with the links loose so you can move them where you need to, and then the severe-duty double-link version. We opted for the second one, as the vehicle owner intended on running tail pipes on the car for the time being.

These upgraded components will do well to handle the higher horsepower level of the nitrous-injected Modular mill under the hood, and the lighter weight will no doubt help the vehicle react better. However, ultimate control comes down to the damper and spring combination that you choose. We asked UPR for its recommendation based on our subject vehicle, power output, and intended use.

"The 14-inch spring is what we usually recommend for drag applications," said UPR's sales manager, Tony Whetstone. It's a lighter spring rate than stock, so it will compress more, and that combined with the extra height stores more energy in the spring. "That kicks the front up and transfers the weight to the rear," noted Whetstone. "A regular street car would run a 12-250 spring—you're not looking for that much travel in that application." Whetstone also recommended a 12DP150 spring for the rear. It's closer to a factory rate, but it is a little softer to allow the rear to squat quicker.

The springs you use are only as good as the dampers that control them, and to that end, Whetstone recommended the adjustable Strange Engineering struts.

"The Strange strut allows you full adjustability, so you can have a full 90/10 for the track and tighten it back up for street driving," he told us. Sounds like the best of both worlds, and what probably sounds better is that UPR sells them for less than what a traditional nonadjustable 90/10 strut goes for.

Out back, Viking double adjustable coilover shocks were picked. "It's a true coilover shock and gives you individual adjustments for rebound and compression." Designed as a coilover from the first sketch, the Viking shock doesn't use the add-on sleeve that can sometimes cause extra noise, and adjustments are easily accessible unlike some aftermarket models. "If you ever decide to mini-tub the car, this is the same coilover you would need for that application," Whetstone noted. It's always good to plan ahead—we all want to go faster eventually, right?

For the installation, we followed along as Kyle Miller, a technician at AntiVenom in Seffner, Florida, installed the UPR components on a 2004 Mustang GT. The car is Miller's personal vehicle, and one that he regularly races whenever the weather is clear. While it is no longer his daily driver, he does wheel it down to the local 1,320 about 50 minutes away. The adjustable suspension can provide a normal ride quality on the open road, and with a few small adjustments it optimizes straight-line speed from a dead hook at the track.

Before the suspension installation, the car's 60-foot times were vey inconsistent, ranging from the low 1.9s to 2.1s. Now, Miller regularly hits low 1.8s every time. That consistency will allow him to make other changes to the car to improve performance further.

Whether you want to go fast on the strip or the open road course, an aftermarket suspension can improve your vehicle's performance. If you've modified your engine already, your suspension is already overdue for an upgrade.

There's no better way to improve weight transfer to the rear of the car than taking weight off of the front, and the easiest way to accomplish that is by swapping the stock K-member and front control arms with tubular versions such as 2005-96SK kit from UPR. This is a mild-steel version that fits '96-'04 Mustangs and retails for $599.99. It's constructed from seamless tubing and TIG-welded in a billet fixture for accuracy. UPR designed this for the abuse your ride may receive at the track, as well as many miles of street driving.

01. UPR’s sales manager, Tony Whetstone, recommended the 14DP150 coil spring for the front end of our SN-95 subject vehicle. The taller yet softer spring will store more energy than one with a stock-style spring rate and size. Once we let the clutch go, that added energy will transfer the weight rearward much better, resulting in improved traction. The 12DP150 rear spring is close in height to stock, though a bit softer to allow the rear to squat quicker, also aiding weight transfer and traction.

02. At the front of the car we remove the front wheel, brake caliper, and rotor, and then support the lower control arm so we can remove the lower strut bolts. We also need to disconnect the antiroll bar endlink and the ABS sensor shown here.

03. We highly recommend utilizing one of these engine support braces, like the one AntiVenom’s Kyle Miller is using here, when swapping out a K-member. We’ve seen people put jacks under the engine, but we’d rather rely on that as extra precaution than to solely use it to support the 500 pounds of engine above us.

04. The stock steering rack will be swapped over to the new UPR K-member. Here, Miller is unbolting the rack from the stock K-member, and then he supports it in the air until the new K-member is put in place. We did have to swap out the offset rack bushings Miller was using on the car in favor of some stock-style ones.

05. Disconnecting the steering shaft is next. It’s a good idea to mark the shaft and steering rack so you know how everything goes back together. Securing the steering wheel prior to this is also recommended. You can also see in this picture that Miller has removed the engine mount nut in anticipation of the K-member swap.

06. After supporting the K-member with a transmission jack, Miller began removing the K-member bolts along the front framerail. There are two in the wheelwell behind the spindle and two at the back.

07. With the steering rack free, Miller lowered the K-member and control arm assembly. This is much easier to do without a jack underneath the car waiting for you to bump it, hence the use of the top-mount engine support brace.

08. With the new UPR K-member positioned next to the stock unit, it’s easy to understand where the substantial weight savings comes from. The tubular unit is plenty strong for your street car; it’s just much cheaper for the factory to stamp out a K-member than produce it in a tubular design.

09. When assembling the Strange Engineering adjustable front struts, it’s important to get the parts assembled in the correct order. Also, Tony Whetstone of UPR recommended his company’s 2025-07 hardware kit ($69.99), which replaces nearly all of the stock fasteners with new hardware. You never know when you might snap a fastener off or strip the head on a rusty bolt, and this kit takes away the worry of where to find the odd-sized fasteners should one get jacked up during removal.

10. Complementing the tubular front suspension is a pair of UPR Billet Shark Caster/Camber plates. The company CNC-machines these beauties from 1/2-inch-thick 7075 billet aluminum, and they are available in satin or polished finishes. Caster/camber plates should be considered mandatory whenever you lower a vehicle, as the factory plates do not have the adjustability to compensate for the resulting changes in alignment.

11. Once the K-member is hoisted into place and secured. You can begin installing the control arms, spindles, and struts. Having fresh hardware makes all of this easier.

12. The Strange adjustable struts are very easy to set the ride height on. Miller uses a brake tool to adjust the collars, which don’t take much effort to turn. To get in the ballpark on ride height, Miller tightened the adjusting collar up about an inch from the bottom, and then set the car down before making any more adjustments. As it turned out, it was right where he wanted it the first time.

13. The steering rack goes into place, but not before Miller adds the UPR extreme bumpsteer components (PN 2009-94-EXT, $139.99) on the ends. The parts are made from 7075 aircraft aluminum and 4140 chromoly steel for excellent durability, and have a ton of adjustment built into the design. In this picture, you can also see the strut has been installed and the antiroll bar end link reconnected to the new control arm.

14. The new front suspension installation is complete. In addition to reducing weight, you’re also gaining header clearance, starter access, and room for a bigger oil pan. Whether or not you need this now, you likely will need it if you keep heading down the modification path—it’s always good to have room to grown into your parts.

15. Pictured is the UPR Race Pro Series rear kit (PN 1999-K-R, $799.99). The double antiroll bar is a bit overkill for our relatively mild application, so we exchanged it for the single version with extra clearance for tail pipes. You won’t find any urethane bushings in this setup, as it is designed for maximum performance.

16. The rear of our subject vehicle already had some aftermarket control arms, but there wasn’t much control going on given the inconsistent short times. The coil springs were also designed for a lower ride height and tighter handling through the turns, which isn’t the direction this build is going.

17. There are numerous options when it comes to rear shocks for Mustangs, and this Viking double-adjustable package from UPR is among the best. It’s a true coilover shock (the same one you’ll need if you ever mini-tub) with 19-way adjustment of compression and rebound. They bolt right onto your Mustang in the factory shock locations using the included brackets. They will also save you 3 pounds per side over the stock shock/coil spring setup.

18. “We highly recommend our upper and lower torque box kit whenever you’re drag racing with sticky tires,” says Whetstone. Indeed, the factory torque boxes are already prone to coming apart even under regular street driving, and that problem is only exacerbated when drag racing or sticky tires are part of the plan.

19. Some assembly is required with the Viking shocks, such as installing the clips that hold the lower spherical end in place. The upper bracket bolts into the stock shock top mount location.

20. The included lower bracket simply replaces the stock one. Viking recommends starting in the middle on your compression and rebound adjustment as the baseline, and working off of that to fine-tune the action depending on launch parameters and track conditions.

21. The lower control arm torque box support braces require a bit of trimming to the torque box itself in order to fit the bracket up inside. Basically you just need to remove the small lip that goes around the edge. You can reweld additional supports in that area once the brackets are up in, but none are required.

22.The upper support bracket can be a bit tricky to drill the holes for with the rear axle and tailpipes still in the car. A right-angle drill will make things easier, but it is possible to drill them with a standard one.

23. The lower brackets have a matching pair on the top side of the chassis to sandwich the floor between them for added strength. Your back seat goes right back into place and covers them up. All necessary hardware is included.

24. Moving onto the installation of the control arms, the upper bushings on the rear axlehousing must be removed to install these new aluminum pieces. An air hammer will make quick work of their removal. Use an antiseize lubricant on the bushings to prevent them from becoming one with the housing ears.

25. As a baseline, adjust the control arms to the same length as the ones you are replacing before installing them. From there, you can adjust both the uppers and lowers to set the pinion angle.

26. Since we had both in our possession, we wanted to show you both the double antiroll bar and the extra-clearance antiroll bar. UPR also offers a standard one as well as one with the arms loose and waiting to be welded in your position. Whatever your race car needs, UPR has you covered.

27. With the antiroll bar installed, you can see it is a tight fit with the tailpipes in there, but everything cleared and there are no interference noises to report. What we can report is a consistent reduction in 60-foot times by a tenth of a second or more. With the car consistently hooking, owner Kyle Miller can concentrate on bumping up the nitrous jets and leaving the line a little harder for even better elapsed times.