How to Restore Your Lower Control Arms

How to Restore Your Lower Control Arms


 

 

[Mustang Front Suspenstion and Upper Control Arm Rebuild Guide] 1

These aftermarket lower control arms from Global West Suspensions begin life as factory stampings but get a few clever upgrades to make them better. The first of these is that the opening on the lower side is closed off (“boxed”) to greatly increase the strength of the arm. Special-cut plates are fully welded around each seam to completely close off most of the lower opening of the arm, so dirt and moisture cannot accumulate and cause rust. It’s not really possible to close off the whole underside because access must be left for the anti-sway bar end link nuts. The other major improvement over the stock arms is the use of a flanged spherical bearing instead of a rubber bushing at the end that mounts to the body. This type of joint is far stronger and more stable than a rubber bushing; it also has less friction, which actually improves the ride a bit. It is much less prone to wear and pounding out, plus the flanges help prevent unwanted movement of the adjusting bolts that are used to set the wheel alignment. Using bearings instead of bushings improves ride, handling, and durability while being virtually impossible to detect, unless someone crawls under the car to look. If we were building a racer or a higher-performance street car, we may have chosen tubular arms instead. Because we won’t be using the car that aggressively and we want to keep a stock look, this is the type of modification we want—one that greatly improves function with minimal change in style. This is a truly bolt-in upgrade that works very well indeed.

 

 

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Another subtle improvement is the use of special “Lock Out” plates instead of the standard eccentric cams to adjust the position of the lower control arms. The factory eccentric plates have several inherent design weaknesses that can show up over time and/or with too much enthusiastic driving. The factory bolt has a flat side ground onto it that is meant to line up with a step in the offset hole in one of the corresponding plates. This basically indexes the plate to the bolt, so it cannot rotate on it; at least that’s the concept. The hole in the other plate is round so it can go all the way to the head of the bolt, and it’s free to rotate. The problem is that there is too much slop or tolerance between the flat on the plate and the bolt; they just fit too loosely from the start. Over time, the tolerance increases because of use and corrosion. It’s mainly friction and the clamping force of the bolt that prevent the plates from slipping, so you need to have as little play between the bolt and the plates as is possible. If the bolts loosen because of wear or extreme loading, it’s very likely the plates may move and throw the suspension out of alignment. A better approach is to use thicker plates with a series of offset holes, which are fixed in place by the same retaining flanges that locate the stock plates. The difference is that these new plates can’t rotate and the holes in them are much closer to the size of the bolts that go through them. This greatly reduces any potential for movement after the whole assembly is tightened down. Rather than loosening the bolt to turn the plate you have to disassemble the whole system and pick a different set of holes in the plates to get the position of the lower control arm that you want.

For lower control arms, there are many options. Those building a daily driver or a show car generally just go with stock replacement parts, albeit most likely with different levels of quality and/or preparation. Those building a more performance-oriented vehicle with minimal concern over retaining the factory look probably go with aftermarket tubular arms if the budget permits it.

 

 

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This side-by-side comparison of the stock eccentric-plate-style adjusters reveals the inherent advantages of the Lock Out plate. The Lock Out plates (left) fit the retaining flanges much more snugly and make much more contact along each side. The stockstyle plates (right) only have point contact with the flanges and fit more loosely. These plates are also thinner, so it is more likely they can flex under load and thus lose their adjustment as they move. It is also more difficult to keep the stock plates from moving during the adjustment process because the rotation of the plates affects their adjustment. The Lock Out plates are relatively restrained in the horizontal direction and can only move vertically during installation. Choosing different combinations of holes results in movement in both directions, but the plates are locked into position when resting between the flanges. The Lock Out plates are clearly a superior design for any application but are really only needed in higher-performance and/or racing situations.

We took a mid-road approach, which provides most of the benefits that switching to a tubular arm provides, yet does not sacrifice the stock appearance. As you see in the following photos, the change in appearance is relatively subtle, even though the improvement in performance is quite considerable, and noticeable. Installation is also not much different than stock.

 

 

[Mustang Front Suspenstion and Upper Control Arm Rebuild Guide] 04

Lock Out plates are designed so each plate can be repositioned to yield a virtually infinite number of possible locations for the lower control arms. There are six possible combinations of holes in each plate (three per plate with front and back variations), plus the plates can be rotated. This provides more than sufficient adjustment range to find the setting you need. Each plate is marked with numbers for each hole to help ensure the two plates at each control arm are properly matched with each other. There’s a trick in how the plates have to face each other, but it’s explained in the instructions that come with them. It’s a bit tedious, but you should only have to do it once because these won’t wear or move like the stock components. If you’re using lower control arms with flanged bearings, as we did, the plates shouldn’t move or deteriorate over time because the plates and flanges clamp are firmly clamped together. While it may take more effort to set the alignment the first time, you can rest assured it will be far less likely to change over time.

The upper control arms are the parts most likely to simply be rebuilt, though they can still be enhanced somewhat. As long as the main stampings are in good shape (no major rust, corrosion, or cracks), they can be reused after some cleaning. A run through the media blaster and some good paint should be all that’s needed to prepare them for reassembly. The choice of components used during reassembly can be optimized a bit, as I show in the photos. Aftermarket tubular upper arms are also available for those who use their higher-performance and/or racing vehicles more aggressively.

 

Upper Control Arm Rebuild Step by Step

 

MUSTANG RESTORATION: UPPER CONTROL ARM REBUILD- STEP #1

[Mustang Front Suspenstion and Upper Control Arm Rebuild Guide] 5

Rebuilding the upper control arms is not especially difficult, but it does involve some special procedures, which we will cover in the next few photos. All of the parts needed for a typical rebuild are shown here. Note that the control arms we used accept fourbolt ball joints (left). This design is a better choice than the threehole design on the right because it is stronger and uses a more easily found ball joint. There’s no real functional difference other than the greater load handling capacity. The shaft and nut assemblies can be reused if they are not worn or otherwise damaged. New ball joints should always be used along with new grease seals/boots and zerk fittings. We’ll upgrade the spring perches, shocks, and springs, but first we need to make sure the platform they work from is both properly assembled and adjusted. There’s not quite as much potential for improvement with the upper control arms as there is with the lowers, but attention to detail can still pay significant benefits.
[Mustang Front Suspenstion and Upper Control Arm Rebuild Guide] 6

When rebuilding upper control arms, make sure the threads on the arm itself and the retention nuts are in good shape. It’s common for these to strip or wear to the point that new parts are required. These parts should be as clean and free of any surface irregularities as possible before you assemble them. If the nuts still don’t turn freely in the arm, use some anti-seize compound or grease to make sure they do. The nuts will be fully tightened down to about 120 ft-lbs or so (check the factory manual) on the arms so you don’t have to worry about the lubricant making them prone to loosening. Similarly, the grease that goes on the ends of the support shaft lubes the insides of the nuts, so you can be sure that some grease migrates to there anyway. Liberally grease the threads of the shaft and the ID of the seal prior to installing the rubber seals on the shaft. Also grease the interior of the retention nuts. Use relatively tacky grease that does not run out if it gets hot or wet. Be generous since both the type and amount of grease used will play a big role in reducing wear of the shaft/nut threads over time. The grease also helps make the control arm rotate more freely once everything is assembled, so also coat the face of the seal where it contacts the control arm. This will not only reduce “stiction” and improve the ride quality somewhat, but it will help reduce seal wear as well. There’s no need to pack the inside of the nuts with grease. Just make sure there’s enough to coat the threads fully and have a little left over for insurance.

 


MUSTANG RESTORATION: UPPER CONTROL ARM REBUILD- STEP #2

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After all of the parts are assembled, it’s crucial that you center the shaft in the control arm. Do this by measuring the distance from the inner surface of the control arm to the center of the mounting bolt hole on each side. You can also use one of the edges of each hole. Be consistent and make sure the point you use is the same distance from the control arm on each side. If there is a difference, just rotate the shaft in the correct direction to balance it out. Don’t worry about how the seals look or if the letters on the shaft are showing. The critical requirement is that each hole is the same distance away from the inside of the arm so that the arm is centered.

 

MUSTANG RESTORATION: UPPER CONTROL ARM REBUILD- STEP #3

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Before installing the upper control arms on the vehicle, it is a very good idea to just rock the shafts back and forth to loosen them up a bit. This also helps properly seat the seals and make sure the grease is properly distributed. Do not rotate the shafts too far. If you do, they are no longer properly centered. Just rocking them back and forth through about a 120-degree arc should do it. You will likely need a fairly long (and strong) tool to get enough leverage to move the shafts, at least at first. Be sure to avoid damaging the shafts or their mounting holes. Any scratches, scrapes, or gouges could increase the chance of breakage under heavy loads. When the shafts can turn somewhat freely, still with some drag, you’re done.

 

MUSTANG RESTORATION: UPPER CONTROL ARM REBUILD- STEP #4

[Mustang Front Suspenstion and Upper Control Arm Rebuild Guide] 9

The mounting bolts should be pressed into the control arm shafts rather than trying to pull them in by tightening the nuts. Pressing them in with a hydraulic press or similar equipment ensures the bolts are fully seated; the serrations shown are completely engaging the shafts. It also helps avoid damage to the inner fender apron and/or to the bolt threads. With the bolts fully pressed into the arms, inspect and clean the threads with brake cleaner (or similar) if needed.

 

 

They generally won’t be cost effective for a simple daily driver and clearly won’t have the authentic look wanted for a show car. As with the lower arms, we were able to improve performance over stock with minimal difficulty, expense, or change in appearance.

 

[Mustang Front Suspenstion and Upper Control Arm Rebuild Guide] 09

The finished control arm assembly is ready to be installed into the vehicle with the exception of the spring perch. That is discussed shortly. When installing the ball joint, note that relatively little torque is often required, sometimes only 18 ft-lbs. The force of the spring and the weight from the vehicle basically push down on the ball joint in the upper control arm so the bolts serve more to locate it than to help bear this load. Be sure to install the grease boot, but wait until the control arms are in the car and are loaded before fully greasing the ball joints. This is due to how the internal structure of the ball joint changes under load. The best approach is to lightly grease the ball joints when they are installed on the control arms and then go back and fully grease them when the load from the spring/car weight is applied. Grease the shaft, however, before the arms are installed. This is due to the difference in sealing technique and also the lack of access to the zerk fittings after the arms are installed. Make sure you fully seat the zerk fittings into the retention nuts else you may have clearance problems with the shock towers. Fully grease each side until you see grease just starting to come out from under each seal. Use the same type of grease you used.

Different vehicle applications have slightly different hardware combinations, but the procedures and components shown should work with all but the most unique combinations. In many cases, parts can be interchanged and care should be taken in deciding which to use. I point out a few of these issues as we proceed.

 

 

[Mustang Front Suspenstion and Upper Control Arm Rebuild Guide] 10

Our choice of springs and shocks for the front suspension was fairly conventional, yet also quite an improvement. The valving of the Koni Classic shocks is optimized for applications like ours. They are designed for aggressive street driving and not competition, but they certainly can be used for mild track day events. Likewise, they are fine for daily use, though they are a bit stiffer than a regular replacement shock and they will cost more. They are extremely well made, high-quality, non-adjustable shocks that will surely prove durable in our situation. We chose slightly higher- rate springs from Global West Suspensions. These also lowered the car in the front to match the lowering we would be doing in the rear. This mild lowering gives the car a more desirable stance and also helps to lower the center of gravity for better handling and braking. The higher spring rate will stiffen the ride a bit but the tradeoff is worth it in our situation. The combination of slightly higher rate lowering springs along with the improved shock valving should complement each other very well.

Rebuilding the control arms is the major task when restoring and/or enhancing the front suspension of your early Mustang. The remaining work mostly involves choosing the appropriate components to install for your application. As you see in the photos, we went with high quality components that offer a significant performance advantage yet look similar to stock components. Some of these may not really be necessary in a daily driver or correct for a show car. We chose them to be consistent with our desire to make meaningful improvements where possible, consistent with our intended use of the car as a weekend cruiser.

 

 

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Spring perches are one area that is often overlooked on early Mustang suspensions. These parts can often be the source of unwanted noise and handling issues. Any restoration project should involve inspecting their rubber bushings, at minimum. If the bushings are in good shape, these can be reused in a daily driver or even in a show car, if desired. It’s generally a better idea to replace them with new parts. The cost is low and the car is already apart. You can also upgrade to perches that use polyurethane (shown) instead of rubber bushings; we did, because the polyurethane minimizes unwanted compliance and can improve dynamic performance. There may be a very slight increase in noise and vibration, but we were willing to chance it. When using this material, be sure to use a part that has a provision for greasing the bushing because this minimizes the potential for any squeaking noises that can develop. A zerk fitting also helps improve durability because the grease reduces wear. It is best to grease the perches and rotate the shafts a few turns before installing them on the vehicle to make sure the grease is evenly distributed. Our perches were also plated to prevent rust and corrosion, a very nice feature. For the ultimate in functionality, some companies make spring perches that use bearings instead of bushings. These eliminate almost all compliance and reduce friction, though they also transmit more noise and vibration to the interior. They’re also more expensive, but this may be of no consequence to those building a higher-performance street vehicle or race car.

For high-performance levels and/or those building racers, there are additional options like coil-over shocks and tubular anti-sway bars, for example. These can undoubtedly provide additional benefits in a more aggressive driving situation, but they cost more and diminish the factory looking appearance.

 

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