OPTIBELT timing belt (ZRK 1079) synchronises the crankshaft and camshaft with tooth-pitch accuracy measured in hundredths of a millimetre — preventing valve-to-piston contact that would destroy the engine if the belt skips or snaps. Belt construction data — Number of Teeth: 138, Length [mm]: 1315 mm, Width [mm]: 23 mm, Packaging length [cm]: 20, Carbon cm — reflects the tensile load the belt must sustain at peak RPM, with an HNBR or EPDM compound chosen for the specific temperature range of your engine bay. Tooth profile, pitch, and width are specified for the camshaft drive on VOLVO engines; always replace the tensioner and idler pulleys simultaneously to prevent premature failure. OE cross-references: 09CD81, 138HTDP23, 1987949626, 22727 and 21 more. OPTIBELT timing belts are tested to OEM replacement intervals and carry a service-life certificate verifying the compound meets the manufacturer's durability specification. Timing belt replacement intervals vary by manufacturer — typically every 40,000–100,000 miles or 4–6 years, whichever comes first — and must be followed strictly because a snapped belt on an interference engine causes catastrophic valve and piston damage. There are rarely visible warning signs before a timing belt fails; some belts may exhibit surface cracking, fraying, or a glazed appearance, but many break without warning — this is why interval-based replacement is essential. Timing belt replacement is an advanced DIY job requiring careful crankshaft and camshaft alignment, a torque wrench, and engine-specific locking tools — budget 3–5 hours and consult a workshop manual for your exact engine code. When replacing the timing belt, always fit a new tensioner, idler pulley, and water pump (if belt-driven) at the same time — these components have the same service life, and a failed tensioner will destroy the new belt. Investing in a quality timing belt kit now prevents the most expensive engine failure a vehicle can suffer — a belt-related engine rebuild typically costs 10–20 times the price of the belt kit itself. Every part is dispatched with tracked delivery and a 14-day money-back guarantee with hassle-free returns.