Tried the lace-through-holes trick on my cracked bumper and it held up better than expected

I did almost the same thing on my old Corolla about three years back, except I used heavy waxed shoelace from a work boot since I had one sitting in the garage. The bumper had split near the wheel arch and I could not justify a new cover for a car worth maybe two grand. That repair is still on there and the car sees daily driving, rain and all. One thing I learned the hard way is to back the lacing off slightly before tying off. I pulled mine drum tight like a bootlace and the first cold snap made the plastic flex and snap one of my holes wider. After that I redid the end with a little slack so the panel could move, and it has been fine ever since.

Your point about spacing rings true too. My early holes were cramped and the cord sawed against itself on the curve, so halfway down I switched to wider gaps and it sat much flatter. Also worth leaving the cord ends long and melting a blob on the tips so they never work back through the holes. I used a match for mine.

The silicone over the knots is a smart touch I skipped. Mine weeps a tiny bit at the bottom hole after car washes, nothing serious, but I might go back and seal it one of these weekends.

I went with a backing strip instead of stitching on my old Ranger's bumper after it cracked near the tow hook. What I did was grind a shallow V groove along the split with a Dremel, laid a strip of fiberglass mesh behind it, then filled the groove with JB Weld Plastic Bonder working it into the mesh like you'd grout tile. Sanded it flush the next day, hit it with some black bumper paint from a rattle can, and three winters later you have to look hard to find the line.

The reason I didn't try the lacing method is my crack ran right where the bumper flexes most when I push on the panel by hand, and I figured any cord through holes would just create new weak points where the plastic could tear between them. Your silicone over the knots is a smart touch though, that was my worry with any hole method, water getting in and freezing in winter.

One thing that surprised me with the epoxy route is how forgiving it is on fit. My crack edges didn't line up perfectly, maybe a couple millimeters proud in one spot, but the filler bridged it fine where lacing would have shown every misalignment. If you ever do pull the trigger on a replacement cover, the epoxied one would probly survive being popped off and kept as a spare.

This is the first time I've seen someone sew plastic back togehter like a shoe, my brain kind of hurts in a good way. My bumper just has a chunk missing from backing into my mailbox, so nothing to stitch, but now I'm wondering. Does the cord hold up when you blast the bumper with a pressure washer, or whould the holes start to stretch out over time?

Update: finally ran it thru a pressure wash at the coin wash to answer the question upthread. The silicone stayed on every knot and the cord didn't budge, just let a little water through one hole where I nicked it. Also been thinking about that groove and mesh idea since the corner where the cord rubs is starting to fuzz. Might do a hybrid, stitch the long split and fill just that one spot.