HM GTS Front Lip Installation

Work in a dry space that's comfortably warm so the adhesive bonds well. Lay out the upper lip, the lower splitter, and the included hardware so you know what goes where. Before you start, confirm the factory fasteners the lip reuses are still on your bumper and in good shape. Clean the lower bumper surface where the lip mounts with isopropyl alcohol and let it fully dry, so the adhesive has a clean surface to grab.

First, remove the two gloss black pieces on the lower outer edges of the bumper. They come fitted from the factory and are sometimes called splitters. They are gloss black rather than paint-matched to the car, which makes them easy to identify. It is also worth backing out the OEM hardware the lip will reuse, as it can get in the way of a clean dry fit.

With the adhesive backing still on, hold the upper lip up to the bumper and line it up with the factory attachment points. Start at one edge and get it sitting right, then do the other edge, and leave the middle for last. Working edge to edge and finishing in the center helps the lip pull in evenly and keeps the gaps consistent. Check that it sits flush across the full width and that the gaps are even before anything is bonded or tightened.

Once you're happy with the fit, start the fasteners the same way you dry fit it: one edge first, then the other, and the middle last, so the lip pulls in evenly. Use the reused OEM fasteners at the factory attachment points along with the included hardware. Keep them hand-tight and snug rather than cranked down. The small trim screws and clips thread into plastic and only need to be snug, so over-tightening can strip them. If you reuse any of the larger bumper mounting bolts, BMW torques those to roughly 27 Nm (about 20 ft-lb), so treat that as a ceiling and do not exceed factory spec. With the hardware set, peel the 3M backing and press the lip firmly from the center outward so the full contact area bonds.

Bolt the lower splitter to the upper lip with the supplied hardware. It mounts through adjustment slots, so you can set how far it projects before tightening. Dial in the look you want, make sure it's even on both sides, then snug the hardware firmly by hand without cranking it down, to avoid stressing the carbon. The splitter can also be left off if you'd rather run the upper lip on its own.

Go back over every fastener and confirm it's snug, and check that the gaps are even and both pieces sit flush. The 3M adhesive grabs quickly, so you're not waiting around, but the more time you give it to cure before driving hard or washing the car, the stronger the bond will be. Try to avoid pressure-washing the lip directly in the first hours after install.