It’s critical to understand one fundamental rule when it comes to guitars: never, under any circumstances, put steel strings on a guitar designed for nylon strings. Doing so will lead to serious and irreversible damage to your instrument. You should exclusively use Nylon String Guitar Strings on classical guitars.
The critical difference lies in tension. Steel strings exert significantly more tension on a guitar neck compared to nylon strings. Guitars built to handle steel strings, like acoustic guitars, are constructed with robust, reinforced necks. These necks incorporate a metal truss rod, an adjustable component specifically designed to counteract the immense pull from steel strings.
Classical guitars, however, are engineered for the lower tension of nylon strings. Their necks are typically built without a truss rod, relying solely on the wood’s inherent strength to manage the gentler pull of nylon. Furthermore, the body, or “top,” of a classical guitar, along with its internal bracing and bridge, is braced and constructed to withstand only the lighter pressure exerted by nylon strings.
If you mistakenly string a classical guitar with steel strings, the consequences can be devastating. The increased tension will cause the neck to bend and warp permanently. The guitar’s top will distort and “belly up” under the excessive pressure. Ultimately, the bridge, which is glued to the top, will likely tear away, taking a chunk of the top wood with it. This type of damage is often catastrophic and economically unfeasible to repair, effectively ruining your guitar.
To illustrate the dramatic difference in tension, consider the data from string manufacturers like D’Addario. A standard set of regular-gauge steel acoustic guitar strings applies approximately 179 lbs (81.3kg) of tension to the guitar. In stark contrast, a typical set of nylon strings generates only about 83.6 lbs (37.9kg) of tension. Therefore, using steel strings on a classical guitar more than doubles the stress it was designed to endure, leading to the damage described.
