Why They Choose A Timing Belt Instead Of A Timing Chain?

The biggest difference is that a timing belt HAS TO BE changed every so often or it will break and possibly cause damage to your engine.

A belt is made of rubber and fabric. On many engines when they break the engine is badly damaged. It is normal to replace them anywhere from every 60,000 to 90,000 miles. Its different on every engine, its important that you know how often to change them on your particular engine.

A chain is made of steel. They typically stretch and make noise long before they break. Timing chains in general do not need to be periodically replaced.

In many cases, a timing belt makes more sense than a timing chain. For all its advantages, a timing chain is noisier, less efficient, and more expensive than a timing belt. Since an OHC timing chain is very long, a timing belt actually has less lash and stretch resulting in better camshaft timing and improved efficiency. However, while a timing chain may last the life of an engine, a timing belt has specific requirements regarding how regularly it needs to be replaced. If you have a timing chain instead of a timing belt, signs that your timing chain may need replacing would include loss of power and noise from the timing cover at the front of your engine. Unlike those using belts, you probably won't destroy your engine by running with a worn out timing chain. However, you may just get run over by a semi on the interstate, trying to accelerate with that clapped out engine and its stretched timing chain!