Reducing Understeer

Compiled by: Bill Gregory (sansho@rennlist.com)

Date: December 1, 2002

Any of the following actions will help to reduce understeer:

  • Lighter front springs (smaller diameter wire)

  • Heavier rear springs (larger diameter wire)

  • Thinner front sway bar

  • Thicker rear sway bar

  • Softer front shock setting

  • Harder rear shock setting

  • More negative front wheel camber

  • More positive rear wheel camber

  • Wider front tires

  • Thinner rear tires

  •  Higher front tire pressure

  • Lower rear tire pressure

  • Wider front track

  • Narrower rear track

With 964's, a typical action is to increase the thickness of the rear sway bar, using either the 1990 C2 21mm bar, or use an aftermarket adjustable sway bar. Another action, for those with 17" wheels, and 205 front and 255 rear tires, is to upgrade the fronts to 225 tires, assuming, of course, that the rim width supports the wider tire width.

Additional notes on sway-bar adjustments: The idea of sway-bar function is to keep the vehicle undergoing cornering force to remain as flat as possible by connecting the wheel assemblies at each end of the car. A car making a left-hand turn, will transfer weight to the right-side (outside) of the car. Stiffer (thicker) sway bars will cause more weight to transfer to the outside of the car. Therefore, if the front-end is pushing (i.e., sticking too well) the front-end sway bar should be loosened and the rear sway-bar tightened. If the chassis itself is stiff enough, a greater proportion of the weight that was being transferred at the front-end will be transferred at the rear-end. That extra weight being transferred at the rear of the car serves to decrease the cornering force (grip) of the rear end, therefore increasing oversteer, which is in effect decreasing understeer.