Performance: Swaying Control
Leveling out the 850 with sway-bars
Story and photos by Budd Stanley
If you remember back when we did our initial testing of the Volvo 850, the massive amount of body lean was nearly enough to make me seasick. In a hard right-hand corner, the driver’s-side of the front bumper was nearly buried into the tarmac, while the rear passenger-side tire was lifted up into the air. This is the result of excess body roll due to worn sway-bars.
There is probably no other part on the car that has so many different names, so just to make sure we are all on the same page here, let’s go over what it is we are talking about.
In the automotive world, sway-bars are often referred to as “anti-roll bars,” “stabilizer bars” or just simply “roll bars,” not to be confused with the same name given to a roll-cage member. Nevertheless, all these names are correct and all describe the job of the sway-bar – to stabilize the vehicle and control body roll. They do this by connecting the right and left sides of the suspension with a solid bar. This bar is designed to have a pre-determined amount of twist which allows the opposite side to react to movements in the suspension.
So, when taking a right corner, centrifugal force along with the weight and balance of the car’s body will make it lean to the left. When the left side suspension compresses, the sway-bar counteracts this reaction with the cooperation of the rebounding right side suspension, helping to level out the chassis. The stiffer the bar, the less forgiving that bar is on the opposite side, allowing for a stiffer and flatter car in corners. The stiffness is usually determined by the diameter of the sway-bar.
However, as there are two sway-bars on a car, one linking the front and one linking the rear suspensions, it is possible to play with the balance of the car. Oversteering or understeering tendencies can be tuned into the car’s handling by playing with different strength bars to provide less roll and more grip to the front or rear. This was of great concern to us, considering the Volvo’s tendency to roll violently in corners, while producing a heap of understeer. To rectify the situation, we turned back to our friends at IPD to see what they had on hand to level out the wallowing 850.
There is a multitude of companies that produce everything from OEM, to sport, to full adjustable racing sway-bars for nearly every popular vehicle. The problem with the 850 is that it is not so popular with the performance crowd, so finding performance products can prove challenging. IPD specializes in Volvo performance products, and one of its best sellers is the 850 performance sway-bar.
IPD has put a great amount of R&D into the design of these sway-bars, particularly due to the delta link rear suspension geometry which requires a very unique sway-bar. From an engineering aspect, they wanted bars that would perform better during aggressive driving, but they also realize that Volvos are also going to be daily drivers, so a huge amount of testing and development went into finding just the right balance of performance, safety and controllability, precisely what this project is all about.
Built from 4140 chromoly steel for long life and durability, the front bar is 5 mm larger in diameter to the rear at 25 mm, while the rear bar is 2.5 mm larger at 22 mm in diameter. These bars are designed specifically for the 850 to level the body roll in hard cornering while vastly improving the understeering characteristics of the car by offering a much more neutral balance.
So, to save time and money, we called up IPD and ordered up a pair of shiny blue sway-bars, and within a few hours, had them installed on the 850, ready for battle. A short test drive on the street yielded an impressive decrease in body roll and indeed a more neutral and responsive demeanour. However, the track is where we’ll get the most out of this modification, and we’ll give a full report after our final track session.
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