KPI is what The OP is asking about. It is the fixed angle the spindle and axle shaft is welded to. KPI cannot change as it is fixed (welded). If you have A set camber (or caster), KPI can not be changed when changing caster,camber unless you change the spindle assembly. A 10 deg will will change your weight jacking less as you turn your kart the A 12 deg spindle. It is for the most part built to suite your chassis. if it was built with 10 ,that’s what you use. there are different roads taken for A manufacture to decide what they use. As A general rule of thumb for me Ive seen more CIK style karts work better with 12 and American laydowns(goldcup) work better with 10. This is not to say one cant make the other work, but for the chassis and setups ive driven this has been the case. Now ill skip scrub for this discussion because I think that is also a MAJOR PLAYER In this discussion also.