Originally Posted by nismosis

You can get ARP extended studs which are about 25mm longer than stock. It depends on your wheels, as some wheels by design are thicker at the hub depending on the offset you order. Then add that to your spacer thickness. My rule of thumb as an engineer is 1.5D thread engagement with an absolute miniumum of 1D on critical bolted joints. That's 1.5 or 1.0 x Stud Diameter. Our studs are 12mm so that equates to 18mm or 12mm min.