Originally Posted by ioxqq
What does it effect on changing the rear shock position?
Well...it is one of those...it depends type of answers...
First, when you laydown shocks you will end up with a softer and more progressive spring rate. More progressive means that as the suspension gets compressed the spring rate increases faster. Also, if you attach the shocks to the inner hole on the a-arms, this will also soften the effective spring rate.
The reason why this is an "it depends" answer, is that sometimes when you soften the rear suspension this can increase rear grip and sometimes it can take away rear grip. If the rear is too soft and the rear of the car rolls over too much it will loose lateral grip at the rear, because there is too much of a difference between the vertical load on the inside and outside tires. This is less of an issue while entering a corner as most of the weight is transferred to the front tires in this situation. However as you start to apply throttle in the middle and exit of the corner if the car rolls too much in the rear due to overly soft spring rates, then you may loose rear grip.
laying down the springs will also make the car feel more lazy when transitioning in chicanes compared to the same spring being stood up.
My setup app "RC Setup Workbench"
available on IOS (iPhone and iPad) or Android devices help explain this among many other points about setup.