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ipd Safety Sway Bars
Phil Singher

Why would one wish to modify a car which is as well-thought-out and carefully engineered as a Volvo? Because Volvo engineers faced inevitable design trade-offs and compromises in building a car that will appeal to a great variety of people and go practically anywhere. For those of us who drive mainly on pavement and don't mind a slight increase in ride harshness, adding (or enlarging the size of) anti-sway bars can offer a substantial improvement in stability and cornering prowess.

What they do:
A car achieves its best traction when its weight is evenly distributed on all four wheels. When cornering, centrifugal force acts on the car's center of gravity (CG) and transfers weight from the wheels on the inside of the turn to those on the outside. The outside springs compress, and the car's body rolls. Shock absorbers help control the rate of roll, but do nothing to limit its extent. As the roll increases, the suspension has difficulty maintaining a perpendicular angle between tires and road, particularly on the outside tires, which are now carrying most of the load. The tire treads distort, and traction is lost. The amount of roll is directly proportional to the height of the CG and the softness of the springs, which is why old British sportscars were slung so low and sprung like bricks.

Anti-sway bars (aka sway stabilizers or anti-roll bars) limit the extent of body roll. This helps maintain a good angle between tires and road, and it feels better to the driver, who can't get much "seat-of-the-pants" feel during the time it takes body roll to get established. When installed in a front-and-rear set, anti-sway bars are a primary means of controlling the steering characteristics of a car. Although they do nothing to alter the total amount of weight transferred, the relative stiffness of the two bars determines the ratio of weight transferred to the front and rear wheels. Increasing roll stiffness in front tends to produce understeer (the front end tends to "plow"); in the rear it tends to produce oversteer (the rear wants to slide and the driver has to reverse his steering input to get the car around the corner). Volvos are deliberately built to understeer a bit, this being the safer of the two conditions. For performance-oriented driving, the desirable trait is neutral steering, and ipd has tuned its bars to this end.

We installed a set of ipd bars on our 122S, which had skinny tires and stock suspension. Installation is similar on 1800 and 140-series cars. No special tools are required, but it is helpful to have an assistant when doing the rear bar. It is important that your control arm bushings are in good shape, since the bars need something to work against -- they are no substitute for replacing worn-out parts. They will not alter your wheel alignment.

Everything in the kit is top notch. Metal parts are plated to resist corrosion (and also to give them a glamorous gold finish), all hardware is aircraft-quality, bushings are polyurethane, and the kit is complete with a jar of special lubricant and detailed instructions with photos and drawings. The front bar replaces the stock .75" installation with a larger 1.125"bar, in about thirty minutes with no problems. As with almost everything ipd makes, fasteners are exactly the right size (with nothing left over), so it takes a bit of muscle-power to compress the end links enough to get the nuts started. The nuts are self-locking, and a fair amount of torque is required to thread them up -- when you're done, you will be sure that none of this will ever fall off.

The rear installation is more complicated. The .75" bar clamps onto the rear axle (there are two different axle sizes in the older cars -- measure the OD of your axle tubes and specify when ordering), and the end links mount through the floor of the car just forward of the trunk bulkhead. ipd provides reinforcing plates to install here; you must bend them to shape to fit your particular case, drill through them and the floor of the car (we relocated our rear seat belt anchors through these plates as well) and then bolt them on. Your helper is important for doing this and for assembling the end links (again just the right size), since you are now working under and inside the car at once. We had an interference problem with our custom exhaust system, which had to be relocated, but there should be no problem with a stock system.

As a less-expensive alternative, ipd offers a kit which simply replaces the stock front bar with a 1" bar. Although this would theoretically increase the tendency of the car to understeer, they claim that this is largely compensated for by the overall improvement in suspension angles and driver feel. For those who are "mechanically challenged," ipd has an expanding network of garages which are licensed by the company to install their products.

How well they work:
Strictly as a subjective evaluation, we were very gratified by the results. The "mushy" feel of the stock suspension is eliminated, and the car is much quicker to respond to steering inputs. Understeer is much reduced, and, as a bonus, so is front-end dive during braking (we have no sensible explanation for this, but it feels like it). The car is more stable in crosswinds, and cornering that would once have made the tires sing barely produces the occasional chirp. One is more conscious of tar strips, and a pothole that would formerly simply have caused a wheel to thump now tips the whole car just a bit. For our individual tastes and driving style, we were happy to make these trade-offs.

The improvement will be less striking in the 1800s, which have inherently better handling than the 120 and 140-series cars. Still, we recommend a set of good anti-sway bars as the single most cost-effective handling improvement modification available. We have continued with further suspension mods on our car, which have produced incremental improvements, but the ipd Safety Sway bars gave the most dramatic results.

For more info on the Web: The ipd Company

The text of this article originally appeared in the July/August 1994 Volvo Sports America Western States Magazine.

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