What Does a Strut Bar Do?
What is a Strut Bar?
A strut bar (or strut brace) is an extremely simple part that connects the strut towers in either the front or rear of a car with the simple purpose of reducing flex in the chassis between these two points. Strut bars are often made of extremely ridged, light weight materials like aluminum, tube steel, chromoly, and even composites like carbon fiber. The effectiveness of a strut bar is entirely dependent on its rigidity which is why the shape and material of the bar must be chosen carefully. Additionally, strut bars will affect each cars performance differently. This page will explain how strut bars affect the chassis of a car, in what applications strut bars are most effective, and how to choose the right strut bar for your car.
The addition of a strut bar will almost certainly increase the rigidity in nearly every car, however, certain chassis are more prone to flexing than others, making the addition of a strut bar more necessary. McPherson strut based cars in particular create large amounts of lateral forces on the top of the strut tower under cornering conditions compared to cars double wishbone suspension. Older cars and some larger sedans can also be more prone to flex over newer performance-based chassis. This flex is often seen through bucking throughout high load corners.
The second question to consider is the location of the strut bar. Front strut bars are extremely effective at mediating bucking in FWD cars while possibly leading to increased understeer. The same can be said for rear strut bars reducing bucking in RWD cars while possibly increasing oversteer. An important consideration is that stiffening your chassis may cause more understeer or oversteer, however, these effects can be reduced through suspension adjustments, creating a setup with similar grip but much more predictable handling.
Performance Improvements from Strut Bars
Everyone will tell you that strut bars improve the rigidity of a car and, in turn, improve performance, but why?
Just like any steel structure, a flexible chassis will act like a spring to a certain extent. When the chassis is compressed due to cornering forces it wants to bounce back. This rapid release of force will often break tire traction before it is regained, the chassis is compressed again, and the process repeats. Speed this up to real time and we have what is called bucking.
When the strut towers are braced through a strut bar, this flex in the chassis is limited and it acts more as a solid structure, allowing the suspension to do its job independently of the chassis. Strut bars also keep a cars alignment in place throughout high load situations. When a flexible chassis in put under load through a corner, the wheel alignment may alter slightly, causing strange handling characteristics and potential loss of traction.
While a strut bar won’t give your car more grip, it will make you car act in a much more predictable way at the edge of traction. The added rigidity will also allow you to fine tune your suspension without external factors like chassis flex playing a roll.
Choosing the Right Strut Bar
Strut bars are one of the most common performance modifications done to cars and because of that the market is flooded with all kinds of different styles and types. To get the best possible performance for your budget there are a few key factors to consider when choosing your strut bar.
First, the design, primarily the shape of the bar. In almost every design decision there is an advantage and a draw back. In the case of strut bars, this comes into play with the shape of the bar. A straight, linear bar is much more resistant to flexing along its axis compared to a bar that is bent up and over the engine. Because of this, straight strut bars can be made from much thinner, lighter materials. In general, it is always best to use a straight strut bar if possible.
As far as the material goes, a sufficient strut bar can be made from a variety of different metals and composites. Steel bars will almost always be the strongest option but will also be the heaviest. Properly designed aluminum and carbon fiber strut bars can be extremely strong at a fraction of the weight. Our Simple Speed Carbon fiber strut bar for example is almost 15 times lighter than any other strut bar available for the Acura RSX.
Second is the strut tower mounts. An insufficient strut tower mount will allow the chassis to flex regardless of how stiff the strut bar is. Because many companies will not publish data on load ratings, it is best to look for a few key characteristics.
The first place to look is the geometry of the mount. A low profile mount that does not extend very high above the strut tower surface is ideal. The mount should also be sufficiently braced such that it will not bend under load. Remember, strut bars counteract compression, so the force will be transferred in the direction from the bar into the strut tower mount.
Secondly, the material of the mount is just as important as the design. Keep in mind that a better design will allow the designer to use thinner and lighter materials. A properly designed mount made out of 1/8 inch aluminum may be just as strong as a poorly designed mount made out of 1/2 inch steel. In general, steel mounts will be the strongest and are the least prone to fatigue over time.
Why should l buy a strut bar?
A strut bar will primarily affect your cars cornering performance. The added rigidity will help mitigate bucking and unpredictable traction loss in some scenarios. A rigid chassis will also allow your suspension components to work as intended, independently from a flexing chassis, making your adjustments much more effective.
What should I look for in a strut bar?
Try to find a strut bar that is straight, with strong mounts. The material choice is largely dependent on your budget and how much weight you are willing to gain. Steel bars will almost always be the strongest, heaviest, and cheapest option. Carbon fiber is extremely strong and light, but more expensive than other materials. Aluminum tends to fall somewhere in the middle for all three categories.
Are Strut bars worth it?
Everyone wants to hear a clear-cut answer as to whether their money is going towards a part that will make a difference in their driving experience. The problem is that every car is different. Most older cars and cars with MacPherson strut suspension geometry will see handling improvements with the addition of a strut bar. For some newer, performance-based cars, with extremely stiff chassis, strut bars are more cosmetic than functional.