BJ wrote:To decrease understeer increase rear stiffness, ie bigger rear anti roll bar.
Negative.
Decreasing rear end grip is not removing under steer.
All changes should be made against the clock. A bigger anti roll bar in the rear is not faster. It just feels faster and is more snappy... So slow and loose. The rear bar rate does nothing to load the front tyres when increased.
Want to rid all under steer you need a wholistic approach.
A proper 'steer' tyre on the front. Federal 595rsr is the best value for money. I'm trying AD050 yoko's next.
Up the rear spring rate to about 6kg with stock fronts and remove the front sway bar completely.
Make new strut tops and aim for about 8 deg of castor. Using the factory bearings in a sandwiched heim joint would do fine. Ghetto pillowballs.
1.5 to 2deg neg camber in the front. 1 on the rear is heaps.
3mm toe out on all corners.
Replace every bush in the car with alloy or urethane.
Solid mount the rear subframe, diff, gearbox supports.
Once you start making power replace all 3 diffs. Once done you can add a front swaybar again. Until then it only serves to tripod the car keeping wheels off the ground.
With the above you'll our steer just about anything with a rego plate. You will also get 4-5k's max from a set of front tyres. Zero toe in the rear will stop the tram lining a little. Front toe out is needed. At least a mm.
Stock geometry is amazing at stock height. Stiffer rear also introduces some anti squat which helps corner exit front end grip a huge amount due to the stock dynamic toe.
Stock bilsteins are not valved hard enough as is.... Look at a proper set of shocks. Ohlins, dms etc.