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Rogue Engineering Strut Tower Bars

"Like a roll bar for your engine compartment!"

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 200 F, 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.

All BMW Rogue Engineering Strut Tower Bars
View All BMW M3 Strut Tower Bars
BMW M3Price
(2002-2006) Strut Tower Bars$319.00  Add to Cart
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Parts Available: RE.STB.E46.R