PSI Stainless Upgraded Brake Line Kit - BMW G80 M3 / G82 M4 2021+All PSI Products Are Dropshipped From The Manufacturer. Lead Time May Vary. When we picked up our G80, one of the main aspects we felt needed work was the brake feel. The standard OEM lines tend to expand under hard driving and ultimately leave you with a weaker brake feel. With the increase in pedal feel and no ability to expand, the PSI stainless brake lines give the confidence to push your G8x M3 or M4 on the track or the road. Our lines are built