Potential solutions for 2005-2009 USA Outback ghostwalking
This thread is only
intended to discuss potential solutions to the “ghostwalking” or abnormal handling symptoms described in the “dangerous on ice” thread. These symptoms are believed to be caused by a chassis and/or drivetrain issue. Topics to avoid in this thread are tire choice, tire tread depth, and driver error. While tires and driver error can certainly exacerbate shortcomings in any chassis, that line of discussion is not the goal here.
To report a safety issue to the National Highway Traffic Saftey Administration
Summary of the ghostwalking symptoms:
In winter driving conditions and especially on ice, some USA 2005-2009 Outbacks appear to have a chassis tuning issue where the rear suspension oscillates in such a way to cause rear-steer. This is not
fishtailing due to using too much gas, lifting off the gas mid-corner, or hitting the brakes too abruptly. This can occur during straight line driving at moderate speeds. Road feel and handling confidence is totally lost when this occurs. The symptoms are not 100% reproducible and Subaru has not acknowledged that there is any problem. Subaru did revise the rear wheel alignment specifications for these cars in 2007 due to rear tire wear complaints. The change to alignment spec tightens the tolerance for rear toe.
Ghostwalking does not seem to affect European/Austrailian/Japanense spec Outbacks, nor does it affect the Legacy cars. The USA Outback is raised an additional inch compared to Outbacks sold in other regions and does not include a load-dependent self-leveling system. It is plausible that the added height and lack of self-leveling feature compromises the suspension geometry and driving dynamics. More study is required.
Because ghostwalking is not 100% reproducible, it is difficult to pinpoint a fix. Through experimentation, several board members have come up with solutions:
Recommend skipping straight to solution #2
Solution #1: 4-wheel alignment with updated OEM specs per Technical Service Bulletin: “05-36-07 JAN 07 Tires/Alignment - Tire Pressure/Rear Wheel Toe-In Specs”. The updated Subaru specs have a tighter specification for rear toe angle. Your car may already be aligned to this spec.
4-wheel alignment with updated OEM specs and 100-300 pounds of cargo in the rear. By adding cargo weight during the alignment process, you simulate “real-world” conditions and the tires should point straighter when the car is loaded down. This is a technique that racing teams use - they align the car with the driver in the seat because the driver’s weight can influence all aspects of handling and tuning.
Replace worn rear dampers. The 2005-2009 chassis dampers (struts/shocks) are notorious for premature wear. The rear end is the worst with a floatly/bouncy feeling after only a few years of use. The fix is to replace the rear shocks with a more robust aftermarket brand like KYB Excel-G/GR-2. Using the 2003-2004 chassis rear KYB shocks is a popular option because they stiffen the rear end considerably and are 100% compatible with the 2005-2009 cars. See the main suspension FAQ thread for more info.
- Cost $100-125 in parts for rear dampers and 1-2 hours labor
- Required: Add cost of an alignment $50-$100
- Optional: Add cost of front dampers $125 and additional 1-2 hours labor
Increase rear spring rate with Rallitek Overload springs. By increasing the rear spring stiffness, the rear suspension geometry, specifically the toe-angle, will change less when going over bumps and cornering. This should help reduce any rear-steer effects. By changing the springs, the overall handling balance of the car will change towards oversteer. Since the Outback chassis is tuned with understeer from the factory, this will actually lead to a more neutral-handling car. But in emergency stopping situations, it may be less safe for under-skilled drivers.
- Cost $150 in parts and 1.5-2 hours labor
- Required: Add cost of an alignment $50-$100
Whiteline rear camber adjusting bushings/eccentric bolts. The Outback chassis with the multi-link rear suspension only comes with one rear-toe adjustment on the in-board rear-most lateral link. A problem with this design is that every time you change toe, you also change the camber. So while the toe-angle may be within spec, it is easy to have a camber angle that is mismatched side-to-side or too far away from 0°. Because the multi-link suspension is designed to gain negative camber during compression (outside tire gains camber during cornering), you don't need a lot of static negative camber to get good handling. In fact, a lot of static negative camber can compromise braking and stablity when travelling straight with this type of suspension design. So, the Whiteline KCA399 kit adds an adjuster-bolt and matching polyurethane bushing to the outboard upper-middle lateral link to allow the camber to be tuned in addition to toe. The Whiteline kit replaces an OEM rubber bushing which may deteriorate with age. In extreme cold, it is possible that the OEM bushings contract or change stiffness enough to alter handling. In many industrial applications, polyurethane performs better than rubber in lower temperatures so it is plausible that a poly bushing might hold the alignment better.