What does a strut brace (aka stress bar or strut bar) do?
The concept of a strut bar is intended on reducing the flex between the front strut towers during hard cornering loads. By reducing this flex, it allows suspension points to remain undisturbed, allowing for the suspension to do it's job properly. This often gives the drive a feeling of increased stability and improved turning response, when in reality, the suspension is reacting as designed.
Who can benefit from a strut bar?
For those that may believe a strut bar is only for "track cars" or "racecars", it is also street driven vehicles that benefit from a properly engineered strut tower bar. Whereas anyone can appreciate the ability for a front suspension to remain constant at all times, other benefits include support of the factory strut towers from "mushrooming". These generally occurs if the vehicle hits large potholes, causing the suspension to compress completely, and then damaging the rim. However, its not only the rim that takes the hit, but the shock tower as well. Over time, if left unprotected, it can cause expensive sheet metal damage.
What about a rear bar?
Since the rear suspension points do not see the same kinds of forces during hard corner (when compared to the front), a rear bar is typically unnecessary in a street application. A rear bar also tends to intrude into valuable trunk space inhibiting the full use of the cargo space. Additionally, for those with extensive stereo modifications (such as a sub-box), a rear bar tends to get in the way. Those companies that offer a rear bar typically do so to offer a visual compliment to the front bar.
What to look for in a strut tower brace?
When looking at a strut tower brace to give you the most benefit, it should have the following features:
- Sufficient protection of the strut tower top (to prevent "mushrooming")
- No pivots or heim-style joints to allow the bar to flex or bend, but adjustable, to allow for intention suspension changes.
- Center bar with minimal bends or kinks (straighter is stiffer!)
- Provide adequate underhood clearance (so not to dimple the hood)
- Allow for suspension changes (for those that frequent the track)
- Made from the best materials available (for lightweight, coefficient of thermal expansion)
Even BMW applied many of these traits to their own strut tower braces when they offered them. For the E36 and E46 models, both used cast aluminum strut tower plates and matched them to tubular steel center bars.
Thermodynamics: Damn, I should have paid attention in that class!
Don't worry, you won't be tested on this subject, however it is relevant when talking about the best materials of creating the best strut tower brace. There is a CTE (Coefficient of Thermal Expansion) for most every material so the key is to use materials that have the LEAST amount of effect when the heat increases (such as in the area of an engine compartment).
This graph illustrates the different Coefficients of Thermal Expansion (CTE) of popular materials used for strut tower braces. As you can see, a strut tower brace made entirely of aluminum or magnesium would be most affected by the elevated temperatures of an engine compartment. This may be fine on a strut plate, but if the centerbar were to expand, this would negate any benefit of the bar since it would change the suspension settings in a negative manner (usually increasing positive camber). Since the heat of an engine compartment can exceed 200ºF, this would cause an aluminum or magnesium center bar to start expanding. Simply switching the center bar to steel would cut the variation by nearly 50%. Of course, switching to carbon fiber would make the expansion virtually immeasurable.
What about Rogue Engineering's Carbon Fiber Strut Tower Brace?
Some may question our decision to offer a competing product, since the Rogue Engineering Carbon Fiber brace fulfills many performance requirements already. In fact, the RACEBRACE chassis reinforcement fills a niche which our Carbon Fiber brace does not fill. Such features include compatibility with specific adjustable shocks and easy access to adjustable camber plates.
The Rogue Engineering RACEBRACE was designed as an alternative offering to the BMW Motorsport factory strut tower brace, which is no longer available. This item was standard equipment on the 1995 BMW M3 GT (350 produced, for Europe only) as well as the 1995 BMW M3 Lightweight (US market). This well engineered brace utilized cast aluminum end plates and a adjustable steel center bar. Frequently sold for more than $500 when available, these rare parts easily fetch $600-$700 on the used market. Unfortunately, this bar did not fit ASC+T vehicles.
The Rogue Engineering RACEBRACE also makes a great replacement for the factory E46 M3 strut brace. These factory strut braces were included on 2002-2006 model year E46 M3s (2001 models did not get it from the factory). Although rare, we have seen the factory cast aluminum mounting plates crack or worse, break. While most are covered under factory warranty, the dealer is usually very quick to deny any warranty because of modifications done to the vehicle (too low, springs too stiff, or a louder muffler was the cause of the crack). While fantastic in concept, the cast strut tower plates are obviously not strong enough to handle the stresses which are being exerted onto the towers from the suspension. The RACEBRACE's solid steel plates offer enough strength to handle these stresses.
Picture of broken factory E46 M3 strut tower mount
| Comparative Features |
Welded
Brace |
Billet
Brace |
BMW
Motorsport |
RE
RACEBRACE |
| Solid, no hinge, no heim-joint, no pivot design |
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| Steel center bar for maximum CTE benefits |
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| Allows access to adjustable camber plates |
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| Allows access to adjustable shocks |
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| Fits ASC+T Traction Control Vehicles |
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| Protective Finish (Paint, Powdercoat or Anodize) |
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| Market Availability |
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| Pricing |
$180-$230 |
$250-$7501 |
$600+2 |
$309-$395 |
1 Replica braces of this type are generally 1/3 the price of the authentic counterpart.
2 No longer available, but when sold used in good condition, they can fetch more than $600
RACEBRACE Features and Benefits
- Lightweight tubular steel bars are 100% TIG welded to high strength steel plates and powdercoated black for a durable finish. While aluminum may be marginally lighter, steel is used for its superiorCoefficients of Thermal Expansion over aluminum or magnesium alloy.
- The RACEBRACE's one-piece design offers the strongest possible connection from each strut tower. Its one piece welded construction resists bending and flexing moments that hinged, flat bars simply cannot compare. While there may be others offering one-piece bars, we engineer our bars to support along the stress of the load path as closely as possible, not just "connecting" the two towers together.
- The multiple bar configuration, with center support bars, resist twisting and bending of the front chassis. Although it does not bolt to the firewall, the bar's multiple tubes resist bending and twisting in multiple planes (when compared to strut braces' that use only flat bars).
- Open tower design allows for easy access to adjustable camber plates and shock adjustments.
- Designed to offer adequate clearance over the engine components as well as underhood clearance.
- Strut tower offers full 360° support, completely covering the strut tower area. This can prevent costly sheet metal damage "mushrooming" from potholes, especially with lowered cars.
- Removal of the strut brace takes only minutes with simple hand tools. Adjustments to suspension camber/caster plates can be made without removal of the bar.
