Chain reaction: It all starts with strong adhesive bonds

(www.serotta.com). The company relies on the bond strength of Araldite 2015 epoxy to securely hold carbon-fiber tubes in polished titanium lugs. The resulting assembly produces a lightweight bike that combines speed with comfort and responsiveness.

Adhesives such as Araldite 2015 from Vantico A&T U.S. Inc., Los Angeles (www.vantico.com), bond to a variety of substrates with dissimilar coefficients of thermal expansion including aluminum, titanium, and fiber-reinforced composites. Bonded joints can withstand bone-jarring vibrations as riders traversing rough single tracks. They also handle temperature extremes and corrosive substances such as salt spray.

Serotta prewelds carbon-fiber tubes and titanium fittings and abrades substrate surfaces to aid adhesion. The epoxy, supplied in dual-barrel cartridges, is mixed and dispensed through a disposable nozzle onto a board. A tongue depressor applies the epoxy to the surfaces of the metal and composite. Next, carbon-fiber tubes are fully seated into the metal fittings. Excess adhesive is removed, and the bonded frame cures overnight in an assembly jig. The process lets Serotta customize bike geometries to fit each rider.

LP Composites, White Salmon, Wash. (www.lpcomposites.com), also uses the adhesive to securely join braided carbon/aramid-fiber components to aluminum-alloy end fittings on accessories such as bar ends, grips, and seat posts for mountain and road bikes. The preformed components are resin-transfer-molded. The process yields precise wall thicknesses with optimized strength and flex. Stu Fisher, president of LP, says the epoxy is easy to use because of its gap-filling and sag-resistant properties. It also attains handling strength after 4 hr at room temperature and produces joints with lap shear strength of 3,200 psi.

Serotta Bicycles uses Araldite 2015 epoxy to bond carbon fiber tubes in polished titanium lugs. The assembly withstands temperatures from Ð67 to 250¡F and retains a 2,500-psi lap shear strength at room temperature.

LP Composites joins braided composite components to metal fitting using Araldite 2015 epoxy. The bike bar ends, grips, and seat posts come in black, natural carbon, and hybrid-carbon-and-gold braid.