A relag that fails three weeks after it went on rarely fails because someone bought the wrong lagging. It fails because something went sideways between stripping the old rubber and rolling the new one down.
That's the uncomfortable part of pulley work: the product does its job almost every time. The bond line is where jobs are won and lost. When our service team went through REMA Tip Top's relagging training, that point came up over and over — the overwhelming majority of failures come back to preparation and installation technique, not the lagging itself.
Here are the five failure modes we see most, and what a clean job looks like instead.
The step people underestimate is oil from bare hands. A prepped pulley face is a bonding surface, and touching it transfers enough skin oil to compromise a patch of it. Once the surface is prepped, treat it like a sterile field — gloves on, hands off.
What good looks like: everything stripped down to clean metal, then a wipe with R50 solvent to lift residual dust and oils, and full dry time before anything else happens.
Adhesive needs mechanical grip, not just chemical grip. A smooth, polished pulley face gives it nothing to bite into. The target is an RMA4 surface profile, achieved by shot blasting or grinding — a consistent, evenly roughened texture across the entire bonding area.
The mistake is roughening unevenly: aggressive in the middle where it's easy to reach, light near the edges and shaft ends. Those under-prepped edges are exactly where lagging starts to lift later.
What good looks like: uniform RMA4 profile edge to edge, with the same attention paid to the hard-to-reach areas as the easy ones.
Here's the one that surprises even experienced crews. After you buff or sand to profile, the surface carries microscopic rubber dust. If you hit it with solvent again at that point, you can melt that dust back down into the surface — creating an invisible weak film right where you need the strongest bond.
The sequence matters. Clean and solvent first, buff to profile second, then bond. Reversing those last two steps sets up a failure you won't see until the lagging starts letting go.
What good looks like: solvent before buffing, never after. Then straight into primer.
Primer and adhesive both need time, and "it looked dry" isn't the standard. PR200 primer wants roughly an hour before adhesive goes on. SC4000 adhesive, mixed with E40 hardener at the correct ratio, wants roughly another hour before the lagging is placed.
Rushing either window — or eyeballing the hardener ratio because the shift is ending — means the bond never reaches full strength. It may hold long enough to look like a successful job, then release under load a few weeks in.
What good looks like: measured mixing, honored dry times, and a crew that plans the job around the chemistry instead of the other way around.
Why this matters more with REMA lagging: every REMA lagging carries a CN bonding layer — a partially cured rubber layer that chemically bonds with the SC-series adhesive through cold vulcanization, completing its cure during installation. That's what makes the bond stronger than standard lagging. But it's a chemical reaction, and chemical reactions don't negotiate. Clean surface and correct timing are what let the technology actually deliver.
Lagging usually starts failing at a seam, not in the middle of a panel. You have three seam options on blanket/one piece lagging, and each has a purpose:
Strip lagging follows the same logic: individual strips butted tightly side by side, with seams sealed using T2 or a rubberized caulk. Ceramic CKX installs the same way, with the sealed seam combining rubber flexibility and ceramic durability.
Whichever style you choose, the finish work is what makes it hold. Rolling, hammering, and stitching the seam drives out trapped air and maximizes adhesive contact. Air in the bond line is a future failure — it's a void waiting to become a lifted edge.
What good looks like: a seam style chosen deliberately for the application and sealed.
Every one of these failures is a shortcut that looked harmless at the time. Skipping a wipe-down, rushing a dry time, letting a seam go with a quick press instead of a full stitch — none of it looks like sabotage on the day. It shows up weeks later as slip, a lifted edge, or a callback.
Done properly, a relag on a sound pulley delivers years of service. That gap between weeks and years isn't the product. It's the process.
Want the job done to protocol the first time? Our crews are trained on the full REMA Tip Top relagging process — assessment through final seam. Contact your Davis rep · 813-247-3620 · conveyors247.com