Battle of the Seiko Movements: 6R15 vs 6R35 Compared 
James Elliott14 November 2021 | 7 min read
Roll up, roll up, it’s time for another movement comparison. This time, we’re putting two movements from the same manufacturer head to head to help you decide which might be right for your next watch.
Specifically, in this article, we’ll compare two great Seiko movements in the 6R15 vs 6R35. Seiko watches are great value for money, and you’ll find they do an equally good job developing movements too.
There’s no time to waste, so let’s get started!
- Seiko 6R15 vs 6R35 – Manufacturer Review
- Seiko 6R15 vs 6R35 – Side-by-Side Specs
- Watch models that use these movements
In a hurry? Here’s the short version:
- The 6R15 was a great movement from Seiko that combined good quality with affordable price. It’s now no longer in production but is a great movement for any second-hand watches you may find in the market.
- You can view the 6R35 as the modern-day upgrade to the 6R15. With this movement, you get 20 hours more power reserve (a total of 70) for watches around the $750 price point. There are the odd reports of poor accuracy though, which is disappointing compared to other movements at this price point.
6R15 vs 6R35: The Manufacturer
Let’s start by setting the scene. Whereas in other articles we’ve looked at movements used for a variety of brands, this comparison focuses on two in-house movements which you’ll only find in Seiko watches. If you’re reading this article, we assume you’re already set on Seiko as your next watch brand of choice and may be weighing up different models which house different movements.
The 6R15 has been one of Seiko’s go-to movements in the past ten years, powering some of its great watches such as the SARB033, the SARB017 Alpinist, and a number of their Prospex diver models, including the SPB079J1. It’s found in watches that typically spanned the $300-$600 range and, at that price, offered reasonable performance.
Saying that, the jury was definitely out on the movement’s performance. Many customers found the movement to lose time far outside of the stated -15/+25 tolerance. While this feedback was mainly anecdotal, the movement gained a slight reputation for unreliability in certain watch circles.
In recent years, the 6R35 has joined the Seiko party. Essentially, you can view the 6R35 as the upgrade to the 6R15. While it is an absolutely identical movement in many ways, the 6R35 utilizes slightly different mainspring components to make it more efficient.
This efficiency leads to one key advantage, a greater power reserve. Whereas the 6R15 delivered around 50 hours of juice, the 6R35 adds an additional 20 hours to provide 70 hours of total power.
You’ll now start to see the 6R35 filter through into Seiko’s most popular watches, including their Presage line (such as the SPB127) and a number of Propex models, including the SPB117. These watches retail at around $700+, meaning you’ll need a slightly higher budget to find a watch with a 6R35 movement.
The Verdict: The 6R35 has come in to replace the 6R15 within Seiko’s lineup. The key improvement is seen in the power reserve, where the 6R35 delivers 20 hours more than the 6R15. Both movements receive complaints about their accuracy, but these are anecdotal rather than widespread.
Seiko 6R15 vs. 6R35: Side-by-Side Specs
Although the movements are practically identical, here are the side-by-side specs to show how they compare.
|Seiko 6R15||Seiko 6R35|
|Functions||Hours, minutes, central second hand, date at 3:00||Hours, minutes, central second hand, date at 3:00|
|Thickness||5.25 mm||5.25 mm|
|Diameter||27.40 mm||27.40 mm|
|Lift Angle||53 Degrees||53 Degrees|
|Frequency||21,600 vibrations per hour||21,600 vibrations per hour|
|Number of Hands||3||3|
|Power Reserve||50 hours||70 hours|
|Accuracy (Per Day)||-15/+25 seconds per day||+/- 20~40 seconds per day|
|Mainspring||Spron 510||Spron 510|
|Country of Origin||Japan||Japan|
|Watch Price Point||$300-$600||$750+|
|Real Customer Feedback – Pros||Solid movement at a good price point.||Solid movement, hacking seconds, bi-directional movement.|
|Real Customer Feedback – Cons||Accuracy can be temperamental, falling outside of quoted tolerance||Accuracy can be temperamental. Harder to compensate for at this price point vs. competitors.|
The Verdict: Both movements are practically identical aside from the power reserve increase on the 6R35 and the subsequent higher cost. It’s worth noting that at this higher price, the movement competes with other movements, which can offer better performance.
Now that you know all about the movements themselves, it’s time to look at some watches. With the 6R15 coming out of circulation, the watches shown are often at the end of their manufacture range or are now on the preowned market, whereas the 6R35 models are still retailing with Seiko.
Example watch models using the 6R35
One of Seiko’s most famous dive watch ranges, the ‘Sumo’, is one of the models that’s recently benefitted from the upgrade to a 6R35 movement as part of it’s 3rd generation launch.
As part of the Propsex range, you know this keeps you safe underwater, with the large 45mm dial easy to read underwater. A sapphire crystal, uni-directional bezel, 200m water resistance, and screw-down crown come together to create a diving masterpiece, with the ever-popular green design trendy and sleek.
And, of course, thanks to the 6R35 movement, you’ve got 70 hours of power to keep you going on your next diving expedition. All of this comes together at a price of around $930, so expect to pay a little more to get that top-tier performance.
To finish up, we’ve pulled out another Seiko great in the Alpinist, this time going for the limited edition SBDC091 reference. The Alpinist watches really are beautiful, with the classic expedition design combined with a very classy green and gold color combination.
It’s a nice size at 39.4mm, with the brown leather strap super comfortable for long-distance trekking over several days. Of course, you’re also getting the premium features you’d expect from Seiko at this level, with a sapphire crystal, 200m of water resistance, and an anti-magnetic finish combining to round off the package.
This Seiko classic will set you back around $700. Given the prestige, style, and reliability of the Alpinist, we think it’s a great price for a watch that not only looks great but is powered by a strong movement in the 6R35.
Example watch models using the Seiko 6R15
One of the best budget Seiko watches ever made, the SARB033 combines classic stylings with great performance, all at a fantastic price – at least, it used to be!
Since the SARB033 left production, the second-hand value of these watches has increased massively as one of the nicest Seiko dress/sport watches around. The 38mm size was perfect for those with smaller wrists alongside the high-quality stainless steel bracelet, sapphire crystal, and Seiko 6R15 automatic movement
Nowadays, you’ll be able to find a SARB033 second-hand for around $700. It’s a high price to pay, but you’ll get yourself a watch that’s assured to look great on the wrist and retain its value due to its popularity. You can find out more about the SARB033 and some great SARB033 alternatives here.
If you’re a fan of dive watches, the Seiko Prospex Recreation (ref. SPB053J1) is an excellent watch that sports the 6R15 movement. This 42.6mm blue dial monster is a great device to have on your wrist when dicing to the depths, alongside looking great when you’re on dry land.
The large markings and high-powered lume make it easy to read underwater, with 200m of water resistance and a sapphire crystal ensuring it’s durable no matter the adventure. The silicone strap is comfortable on the wrist, with the uni-directional bezel a handy tool for keeping track of diving time.
As with many 6R15 watches, this is no longer in production from Seiko, so you’ll be looking to pay around $800 on the pre-owned market to get yourself one of these. It’s a good price for a stylish dive watch that’ll pack a punch when you need it underwater.
Summarising the difference between the 6R15 and the 6R35
When you put the 6R15 and the 6R35 head-to-head, there aren’t too many differences to see on the surface. But the comparison here is a little different, given the 6R35 is now essentially replacing the 6R15 in Seiko’s most popular watches.
The key difference is the additional 20 hours of power reserve in the 6R35, which for some watch fans might be worth the extra price.
Ultimately, your choice between the two may rest on your budget and whether you’re heading pre-owned or brand new. If pre-owned, there are a range of models housing the 6R15 model, all of which will deliver great performance.
If you want a new Seiko, you won’t find many with a 6R15 movement, and thus you’ll be buying a watch with a 6R35. This is no bad thing, as you’re getting an identical movement that delivers great performance with an upgraded power reserve!