Oval chainrings are not a new concept. Don’t believe me? Bring up Shimano BIOPACE to a group of cyclists and you’ll get all sorts of interesting responses. But don’t worry, this is not your Dad’s BIOPACE.
Last year I wrote a full review about the AbsoluteBLACK oval inner chainring which you can read here. That review also includes a bit of background on who AbsoluteBLACK are so I encourage you to check it out for context. In the time since I posted that first review, I’ve put in a lot more miles on the inner chainring and AbsoluteBLACK have released a new oval outer chainring. Based on my experience with the inner chainrings I was really curious to see how well the matching outer chainring would perform. And more importantly I wanted to understand how well they work together as a set.
Through the AbsoluteBLACK ambassador program I was able to pick up the new oval outer chainring and have been throwing everything it. Since my initial review covers the oval inner chainring in detail, this review focuses on the oval outer chainring and the performance of the pair as a set. Below are my thoughts and impressions.
Construction & Design
Let me put it out there, I’m a sucker for design. Especially packaging design. In this regard AbsoluteBLACK does not disappoint. Inside the nondescript delivery envelope I found well designed packaging for the new 50T oval outer chainring as well as the required mounting bolts. On the outside of the packaging AbsoluteBLACK include the same level of product detail as is included with the inner chainring. This will help you ensure you've got the right rings before you start the setup.
The first thing I noticed about the 50T oval chainring itself was its weight. Considering that these chainrings are not hollow forged and are machined from a solid block of 7075 Txxx aluminum, their lightness is impressive. The chosen material, 7075 aluminum, is an alloy which despite its low weight is comparable to steel in strengths but far more resistant to corrosion. I'll explain more about 7075 aluminum throughout the review.
Visually the AbsoluteBLACK oval outer chainring looks like different than anything else out there. This is thanks in part to the ovality (degree of deviation from round) which compared to their 34T inner chainring is much more pronounced. So much so that there is no mistaking that it’s not perfectly round. With an ovality of 10.3%, it’s ~4% more oval than the matching inner chainring.
Aside from its distinctly different shape, the CNC machined detail on the oval chainring is genuinely intricate. While interesting in form, these details are also critically functional. All those stepped nooks and crannies keep the weight down but what’s left is there to ensure stiffness.
Where it really gets interesting is on the backside. You need to turn the chainring over to truly appreciate the attention paid. What do I mean? The back of the chainring is where AbsoluteBLACK have gotten creative in designing a system for effective shifting. Because shifting pins and tooth profiles are protected by patents held by the big brands, AbsoluteBLACK and other aftermarket manufacturers have to find innovative approaches to this critical piece of chainring performance. The machined ramps and recesses that AbsoluteBLACK have come up with are quite elaborate. These shifting ramps work by grabbing and lifting the chain up and over as the derailleur moves outboard. Further in this review I'll cover how well it works.
From a branding perspective the AbsoluteBLACK oval chainrings are devoid of any branding. This helps with their stealthy appearance and if you are like me and like to keep it discreet, these surely fit the bill.
Aside from performance, if you’re researching for information on these chainrings then you are probably wondering what the specs are and how they compare to the stock Shimano chainrings. Good thing I wrote that all down before installing them. Here is a quick comparison against my stock Shimano Ultegra 6800 50T outer chainring.
• 121 grams (claimed 120 grams)
Hardware: 4 double chainring bolts (black)
• 8 grams
Total weight: 129 grams
Shimano Ultegra 6800 50T
• 112 grams
Hardware: 4 short bolts
• 5 grams
Total weight: 117 grams
The total weight difference between the two chainrings is +12 grams for the AbsoluteBLACK. This is so small that it’s negligible unless you are chasing every last gram. However I suspect that if you’re interested in oval chainrings it’s more likely due to an interest in performance improvement so let’s move on to setup and performance.
One thing that cyclists and mechanics alike have long loathed about oval chainrings is their frustratingly complex setup. Don't worry, there is good news here. Because of how AbsoluteBLACK have hard coded the timing of the ovality (where it deviates from round) in the pedal stroke there are no timing adjustments needed. You just need to make sure that the chainrings are lined up properly to the crank arm. Knowing which bolt holes to line up with the crank arm when set correctly is easy thanks to a machined recess that fits in behind the crank arm. Honestly it’s so simple that if it doesn’t feel right, it’s not.
When installing the AbsoluteBLACK oval outer chainring to a 4 bolt 110BCD Shimano (Ultegra 6800, Dura Ace 9000 or 9100) crank you’re going to need know a few things. First the front derailleur is going to need to be raised higher than its normal position for a round ring. The installation instructions on the product page call for raising the front derailleur about 2-3mm. Personally I found this wasn’t enough clearance for upshifting. Instead I lined the front derailleur ~1mm above the teeth at their highest point. Once I had it set this way I was good to ride.
One last thing. If you are going to be using both the AbsoluteBLACK oval inner and outer chainrings together you will require a set of double chainring bolts. The original stock bolts will not work. Of course AbsoluteBLACK sells these double chainring bolts if you need them. These should be torqued to a spec of 5-7nm and for this you are going to need a chainring nut wrench and a torque wrench.
Overall the total process of removal of old and installation of new was straight forward. It took me about 15 minutes but if you’re not so inclined to do this yourself, your local bike shop should be able to do this for you without hassle.
On The Road
Since its arrival I have had the outer chainring with me on every ride. Starting with my own methodology for product testing, the first ride was on the trainer to check the setup and make sure everything was as it should be. It also gave me an ideal environment to ride without any outside influences or distractions. My Wahoo KiCKR trainer also affords for power monitoring which is an interesting perspective. So for this first ride I fired up Zwift and headed for the new mountain pass climb to see and feel what I could.
From the first pedal the greater ovality of the outer chainring was noticeable, but only for a minute or two. Whether I quickly adapted or just forgot about it I’m not sure. Either way, after a few minutes there was no irregular oval sensation. In fact even now, nearly a thousand kilometres later, I don’t feel anything when moving back and forth to bikes with round rings.
Aside from feel (which is incredibly subjective), a big criticism for oval chainrings has been shifting performance. To be honest, my first few shifts were not my best work. Why? From my perspective, if you time the shift at the point where the chainring is at its largest, it’s great. But if you time an upshift when the chainring is effectively at its smallest, there is so much slack in the chain that it causes it to noisily skip while failing to ramp up. This made me realize that I had gotten lazy in timing shifts. Once I got over that the shifting in both directions was impressive. Downshiting is fast and quick thanks to 12 down shifting points and upshifting is sharp and precise thanks to 6 upshift ramps. All machined into the back of the ring. My advice is to add a chain catcher to your front derailleur just to be sure.
To help illustrate the effect of a properly timed shift and a mistimed shift on the AbsoluteBLACK outer oval chainrings I put together a short video contained in this review. Be sure to pay attention to the change in slack through the chain created by the ovality of the chainring shape.
A concern for anyone looking for blacked out parts is always the wear and tear on the finish. To see what I mean take a look at my review of the Pacenti SL23 v1 Black rims for an example of anodizing wearing down.
After ~1000kms of use the finish has held up very well and only shows minimal signs of wear. The black colour and durability is thanks to a Type II anodized finish. The anodizing process is an electrolytic passivation process, usually with sulphuric acid, that adds thickness to the natural oxide layer on the outside of the chainring. This added thickness is what increases resistance to corrosion and wear. The black colour is also thanks to the anodizing process because the sulphuric acid produces a porous surface which allows the aluminum to be died to a nearly endless variety of colours.
Although it’s not bothersome for me, some people have expressed strong feelings about how the chainrings present themselves with the stock Shimano crank arm. Unlike the stock chainrings, the AbsoluteBLACK chainrings do not mount flush. There is an uneven depth between the crank arm and the chain ring which some see as an unfinished appearance. I assume that this is likely part of the design decisions made to help keep the weight down. If this is a problem for you, you could always use the Rotor chainring bolts to help make a smoother transition.
I have no lab or expensive testing equipment so my impressions are entirely subjective to my tastes and experiences. I get that and with that in mind, I’ve been quite pleased with the AbsoluteBLACK oval outer chainring. After about 1000 kms I can’t definitively say that they have improved my performance but I can confidently say that they have had no negative effects to my performance, power output, or enjoyment on the road. At the very least they are a net zero trade to the stock rings. If anything the AbsoluteBLACK oval chainrings add a very visually differentiated look to the bike.
There is little to no oval sensation during the pedal stroke, and the shifting performance is far above expectations. Installation was a breeze and the long term durability has been impressive.
If you are looking for a modestly priced upgrade to your ride and want to take advantage of some innovating engineering then I'd suggest taking a look at and the AbsoluteBLACK oval chainrings.