|Manufacturer||Grand Seiko (Seiko Watch Corporation)|
|Caliber Number||9R31, 9R31A|
|Movement Type||Automatic, Spring Drive|
||C-MOS-IC: Oscillator, Frequency Divider, Spring Drive Control Circuit|
|Functions||Central hours; central minutes; central sweeping seconds hand, power reserve indicator on the movement side|
|Country of Manufacture||Japan|
||Grand Seiko Elegance Collection: SBGY002, SBGY007, SNGY008; Grand Seiko Heritage Collection 44GS 55th Anniversary Limited Edition: SBGY009 (Talk about your watch in the comments below…)|
The Grand Seiko caliber 9R31 (9R31A) is manual winding spring drive watch movement with 30 jewels, made in Japan. This caliber is found in the Grand Seiko Elegance Collection as well as the blue Heritage Collection limited edition released in August 2022 to celebrate the 55th anniversary of the 44GS.
In Grand Seiko’s own words:
“This movement incorporates an innovative Dual-Spring Barrel that contains two mainsprings set in parallel and so delivers a power reserve of 72 hours. The thinness of this movement, the slim construction of the case and the box-shaped sapphire crystal all combine to allow the craftsmen and women of the Shinshu Watch Studio to create a slim and classical design that captures the spirit of the original 44GS, while also achieving a low center of gravity that provides excellent comfort on the wrist.” –source
Some of the topics covered in this caliber listing:
9R65 Spring Drive Tech:
Within the first few pages of the Grand Seiko manual which covers multiple Spring Drive calibers, Seiko’s elevator pitch for the movement technology is: “Taste of a Mechanical Watch ＋ High accuracy equivalent to a Quartz Watch, that is the concept of the Spring Drive.”
Although Seiko introduced Spring Drive at Baselworld 1998, they were working on it since at least 1978 when they filed an initial patent for the technology. The Grand Seiko 9R65 wasn’t officially launched until 2004.
The lapse in time from the launch of Spring Drive to the use in Grand Seiko watches comes down to specs and performance. According to Seiko’s official site, at the time of its unveiling, Spring Drive still wasn’t good enough to be used in Grand Seiko watches (not in those words).
In Seiko’s own words:
“Our company unveiled Spring Drive in 1999, but its lack of a sufficiently effective automatic winding mechanism and 72-hour power reserve prevent its adoption in the Grand Seiko line. After a further four years of development, the first Grand Seiko 9R Spring Drive was created. The winding system and drive time were improved from the existing 48-hour manual winding system to an automatic 72-hour power reserve. The automatic winding mechanism uses Seiko’s original Magic Lever mechanism developed in 1959, but with improved productivity, maintainability, and durability to enhance winding efficiency.” –source
“Spring Drive is a unique watch technology. It generates energy like every other luxury mechanical watch but combines this with an electronic regulator to deliver a level of precision that no mechanical watch can match.
The development of Spring Drive was possible because Grand Seiko is one of the very few manufacturers with mastery of both electronic and mechanical watchmaking.” –source
Glide Motion Hands:
Glide Motion is Grand Seiko’s fancy way of describing the ultra smooth sweeping seconds hand on SD movements.
“The glide motion seconds hand, the visual signature of Spring Drive. Like time itself, it moves smoothly, silently and precisely. The seconds hand of a Spring Drive watch has no “tick” but glides smoothly and silently across the dial. This glide motion hand expresses perfectly the Japanese conception of time as ever-flowing. The speed of the seconds hand is regulated by a magnetic brake that is applied 256 times per second.” –source
9R31 / 9R31A / 9R31B / 9R31C:
The general caliber number is 9R31, with 9R31A being the first version. The subsequent letter variations indicate evolution in the movements development. As of this post, there is only a caliber 9R31A (which is the same as 9R31).
Accuracy of the 9R31:
Seiko officially claims the accuracy of the caliber 9R31 has an average monthly rate of +/-15 seconds per month in normal temperature conditions (between 10 – 60 degrees C). This works out to be a rate of about +/- 1 second per day.
Seiko says this about accuracy:
In other words, they are telling you not to start freaking out because your watch isn’t within the accuracy range for one day, you will have to monitor your watch’s accuracy over the span of a week or so before you can get a real sense of your timepiece’s performance.
The caliber 9R31 holds a power reserve of at least 72 hours/3 days. According to Seiko, it only takes five full rotations of the crown to power the watch to run for about 10 hours. The crown winding direction is clockwise, or forwards. Winding backwards or counterclockwise will do nothing. It is recommended that when winding the crown, the rotations are made slowly.
Note: Seiko says that when the temperature is below 0 degrees Celcius, you should always have at least 1/6 of the power shown by the power reserve indicator.
Crown Position Functions:
- 0 (against the case): Clockwise = Manual Winding / Counterclockwise = Nothing
- 1 (pulled out one click): Counterclockwise / Clockwise = Time setting
How many turns of the crown makes it a full power reserve?
Seiko does not appear to provide this information. If you have a watch with this caliber, please share your experience below.
How often does the 9R31 need serviced?
According to official Seiko documentation, watches with the caliber 9R31 should be overhauled every 2-3 years. Learn all about Seiko service intervals here. At the time of this post, the starting cost of getting this movement services by Seiko is $570.00 USD.
In Seiko’s own words:
“Periodic inspection and adjustment by disassembly and cleaning (overhaul) is recommended approximately once every 3 to 4 years in order to maintain optimal performance of the watch for a long time.” –source (Grand Seiko instruction manual)
“The movement of this watch has a structure that consistent pressure is applied on its power-transmitting wheels. To ensure these parts work together properly, periodic inspection including cleaning of parts and movement, oiling, adjustment of accuracy, functional check and replacement of worn parts is needed. Inspection and adjustment by disassembly and cleaning (overhaul) within 3 to 4 years from the date of purchase is highly recommended for long-time use of your watch. According to use conditions, the oil retaining condition of your watch mechanical parts may deteriorate, abrasion of the parts may occur due to contamination of oil, which may ultimately lead the watch to stop. As the parts such as the gasket may deteriorate, water-resistant performance may be impaired due to intrusion of perspiration and moisture. Please contact the retailer from whom the watch was purchased for inspection and adjustment by disassembly and cleaning (overhaul). For replacement of parts, please specify “GRAND SEIKO GENUINE PARTS”. When asking for inspection and adjustment by disassembly and cleaning (overhaul), make sure that the gasket and push pin are also replaced with new ones.” -same source as above
Replacement prices for the Grand Seiko 9R31A are not available because the movement is not available for individual sale. If you have an issue with your 9R31 powered watch, you should first consider sending it in to a Grand Seiko authorized repair center. During an overhaul, GS may replace the movement at their discretion. If you do not want to have GS service your timepiece, the only way to get parts for repair may be to purchase a used watch on the secondary market. The starting retail price of models with this movement is $8,100 USD.
Examples of watches with the 9R31: