Why do you want to adjust the length of the upper control arms? When I move my hands and try to understand the movement of the rear axle while turning, it seems that shortened upper arms add more toe-in to the outer wheel when cornering. Is that what you want to achieve with the upper adjustables? Or less toe-in, with longer arms? For more steering effect? Or has it nothing at all to do with changes in toe?
Right. Toe in/out is not adjustable on the rear, unless you bend the housing. The upper arm length can only adjust the fore/aft tilt of the rear axle, which really only affects the u-joint/pinion angle. If you would be talking about the front suspension, fore/aft tilt would change the caster.
As said above it is to change pinion angles for better launches. Can the track of the vehicle be changed? Technically yes, under a hard launch a majority of the vehicles weight will transfer to the right rear causing suspension loads to differ from side to side as well as load on the tires. This is why most guys will run different tire pressures from one side to the other as well as adjust the axle location from side to side for a straighter launch. This is not something done quickly nor figured on paper. This is done at the track from one run to the other and dialed in until the driver is happy with the launch performance. You may find driving down the road behind a car that gets run hard and a lot you may see the car actually dog legging or dog walking due to the rear suspension set up. Maybe someone else can explain this better than i.
Alright, it's all about straight line performance. I get it. Thanks! My town don't even have red lights :grin: Would be nice to try how it would affect cornering. Although there are many more problems with the suspension to solve before rear axle dynamics come in to play.
