Rolex’s 3187 Movement
The introduction of the Rolex Explorer II 216570 revealed a few new modern touches to Rolex watches. The outside differences between the 216570 and earlier Explorer II are obvious but what is not so obvious is the new 3187 movement inside the case. Rolex known for its evolutionary rather revolutionary designs introduced a new movement in the Explorer II that adds to the venerable 3185 and 3186 caliber found in earlier Explorer and GMT watches.
Rolex’s new 3187 movement builds upon the technology and evolution found in other Rolex movements. The 3187 utilizes the same rhodium plating on the plates and bridges found on other Rolex movements. The 3187 also utilizes the same bidirectional winding rotor, and Teflon coated wheels within the winding mechanism that are commonplace in Rolex watches. Additionally, the 3187 uses a full bridge holding the balance wheel rather than a balance cock. A balance cock is usually held by one or two screws and does not allow for adjusting balance end shake. Rolex started utilizing a full balance bridge in the 313x movements to keep the balance steady as well as allow for balance staff end shake using two star nuts located just under the bridge. Like the 3185 and 3186 movements found in the older GMT’s and Explorer II’s, the 3187 movement possesses a 24 hour hand and independently adjustable 12 hour hand, and like the 3186 movement, incorporates a Parachrom hairspring inside a Glucydur* free sprung balance wheel. Like the 3186, the 3187 has updated drive wheels that has less hand play as compared to the 3185.
From this point on, the 3187 differ from its older brothers. The primary difference is Rolex’s use of its in-house balance staff shock system, Paraflex. Paraflex is a shock absorber developed and patented by Rolex that claims to increase shock absorption by 50% over other industry standard shock systems such as KIF or Incablock. Rolex introduced Paraflex in the updated Rolex Day-Date II / President five years ago. Like the Parachrom hairspring whereby Rolex relied upon outside manufacturers to produce, Rolex is moving away from KIF shock systems used in its watches for the last 20 years such that it is not dependent upon other companies in the supply chain. The 3187 movement is slightly larger in diameter than the 3186 movement, and slightly thicker and one of the reasons why the Explorer II 216570 comes in at a slightly larger 42mm case over the standard 40mm cases seen in Rolex sport watches. The updated shock system, combined with the other updates (Parachrom, Chromalight, larger Twinlock crown) makes the Rolex Explorer II 216570 one of the most modern Rolex watch.*Glucydur which is comprised of beryllium, copper, and beryllium bronze iron. Glucydur is resistant to shape changes resulting from changes in temperature. Less expensive brands use a bimetallic balance wheel and some older balance wheels have expansion/contraction slices in them to allow for shape changes.