Article by Jeff Valliere
Shimano GRX Di2 2 x 12 RX825 Gravel Groupset & GRX WH-RX880 Carbon Wheelset Review
Complete GRX 2x12 Groupset Weight: 2,937 grams - ~$2,530
Wheelset: 1,394 grams - $1,550
Available now
Pros: Incredibly accurate “set it and forget it” shifting, super easy front shifting, dual control lever ergonomics, easy and powerful braking, shift customization, quality, Garmin (and other computer) integration, ease of setup, battery life..
Cons: perhaps a touch heavy for gram counters (though IMHO, the performance is well worth the weight), difficult to connect app with system, limited gear range (cassette options/RD max capacity).
Introduction:
This past Spring, Shimano released their 2x12 GRX Di2 groupset, with the most notable update being, well, 2x12, but also subtle improvements to the brake/shift lever ergonomics, wireless levers (in line with Dura Ace, Ultegra and 105), a revamped rear derailleur, and a gravel specific front derailleur. Prior to testing the 2x12 Di2, I was using a 2x11 mechanical GRX groupset (for a short while, as I found a great deal on a Trek Checkpoint just prior, which I purchased specifically for this project/review. The 2x11 on the Checkpoint was amazing, but I was quite excited to give the new Di2 a whirl.
I have ridden bikes just about all of my life, raced for many years and spent 14 years working in bike shops as a mechanic, plus working on my own bikes, family/friends bikes for many years beyond that, but is has been quite some time since I worked in a shop and kept my mechanical skills and technical knowledge up to date (aside from keeping up on CyclingNews tech, Tour tech, etc….).
This project was a serious eye opener on how much had changed in 20 years! I had to buy some new tools, do a lot of reading online, consulted with friends, Shimano direct and watch a ton of YouTube videos. It honestly felt a bit daunting at first, especially with a day job, family, a house to maintain, summer trips, other reviews, etc…. Despite it being a bit of a challenge, it has been an amazing learning experience and really helped update my knowledge and mechanical skills.
GRX ST-RX825 Di2 Dual Control Levers:
The dual control levers have been refined to an even more ergonomic shape to provide better integration with flared handlebars and also with some minor tweaks of the ribbed surface texture of the rubber grip surface and an improved texture to the shift buttons (previously dotted, but now diagonal lines for more positive activation when wet or muddy). They also have a sticky coating on them, as was the case on the previous 2x11 levers. The shape of the raised hoods look really pronounced compared to typical road levers, with a very high front, almost exaggerated (in part to contain the coin cell batteries) and I immediately found the benefit of this shape after just my first ride. The raised hoods are a huge advantage to maintain a secure grip and confidence in technical terrain, which I really noticed and appreciated when the road or trails got bumpy and especially on steep downhills, be it dirt and washboard, or even steep paved descents. The hoods are meaty and substantial and there seems to be really little chance, if any, that one might get bounced off of them, at least not easily and it takes much less “strangling” of the hoods to keep the bike under control. I would actually love to see this design bleed over into road levers, as I find it that helpful.
The levers are now fully wireless and communicate via bluetooth with the rear derailleur, which is the “brains” of the system. The levers are powered by two coin cell batteries on each side that Shimano claims will last for several years. The levers being wireless is really nice, as it is two less cables/wires to have to route internally through the frame (a pain in the best of circumstances) and communicates fast and reliably without a hiccup.
The hydraulic brake lever action is enhanced by the lever ergonomics, as the hands rest such that the brakes can be applied to maximum force/stopping power, with just the least amount of pressure with just a single finger. My previous bike had a 2016 105 2x11 mechanical groupset paired with Avid cable actuated disc brakes and my hands would get sore and tired working the brakes on long, steep descents here in Colorado (5-10 mile descents are not uncommon here in the Colorado foothills). Going to hydraulic is a huge step up of course, but the pairing of the new lever with the GRX hydraulic calipers makes braking so much easier, with essentially no hand fatigue on long descents and the modulation is exceptionally good, as I always feel very in control of the actuation. The levers also have an adjustment screw for smaller hands and find this to be helpful when braking from the drops.
While the re-design of the new levers are also better able to accommodate flared bars as mentioned above, they also work just as well with more traditional bars.
Above, mounted on bars with 12 degree flare. You can see the lever itself also has a bit of a flare to it for easier more ergonomic braking. Each lever has a grippy coating on it (a carryover from their fishing products), which adds to braking confidence, especially when sweaty or wet.
The level of configurability here is impressive, with traditional shift “levers” and also an additional thumb button on the inside of each hood. I left my levers programmed as they came from the factory, which felt most intuitive to me (most closely mimicking a traditional shift lever in regards to operation). The right additional thumb button I designated to scroll screens on my Garmin Edge 1050 and the left one operates the Edge 1050 bell. While the buttons are now more pronounced and tactile than the previous ones that were more flush, but I still find them a bit tricky to operate when wearing even thin long fingered bike gloves. Not really a knock on the product, but just something to keep in mind.
If all of that is not enough, you can easily add satellite shifters (that come in different lengths depending on whether you want to mount them on the tops, drops, or aero bars). I mounted mine on the tops on either side of the stem, where I can easily tap them with my thumbs when climbing to shift the rear derailleur up/down. Again, like all of the other buttons, you can assign them any task you please.
GRX RD-RX825 Rear Derailleur:
The rear derailleur is the brain of the Di2 system, which wirelessly communicates with the shift levers, bike computer (if compatible) and the e-Tube application on your smartphone.
The rear derailleur has a flip up cover that reveals a charging port for the charging cable (not included), as well as a sync button and status light that indicates battery level (just by color though), pairing status and adjust mode.
The RX825 is a beefy derailleur and a touch on the heavy side, but it is exceptionally durable and sturdy for rock solid, accurate shifting. I find the added weight here (front and rear derailleurs) to be a very fair trade for the performance benefits.
New for GRX, like on many MTB rear derailleurs is the inclusion of a clutch, which allows for a quick and easy toggle to tighten chain tension when riding dirt, or flipping to off for smooth pavement. I personally just leave it toggled on all of the time, reducing chain slap/movement in general.
The clutch lever above in the “on” position. I only flip it down to remove the rear wheel, though I often forget to re-activate it, but quickly notice how the chain wobble feels and stop to flip it back up.
Cassette options are 12spd 11-34 or 11-36.
I opted for the 11-36 since I regularly ride very steep hills.
GRX FD-RX825 Front Derailleur:
The front derailleur has a big “forehead” that houses the motor and looks much like Di2 road front derailleurs. What sets the RX825 apart though is an additional +2.5mm chainline to allow for wider tire clearance. The motor is strong and powerful, easily, accurately and effortlessly boosting the chain from my 31t small ring to the 48t big ring (17t is the maximum listed range).
Plenty of clearance here with my 700x43 tires
Also new on the E-Tube Project Cyclist App is Shimano’s Front Shift Next, that allows the user to assign any of the shift buttons to control the front derailleur. One tap it shifts up and one tap it goes back down. I personally have not found the need for this, but can see where it would be handy for some.
I do find the front shifting to be much more positive and predictable than a traditional mechanical front derailleur, whether shifting up to the big ring under load or slow cadence, or shifting a bit late to the small ring under load, it always transfers so fast and easy with just a simple tap. Even more amazing, it automatically trims without the need to fuss with micro clicks as you would on mechanical.
GRX BR-RX820 Hydraulic Disc Brakes (with RT-CL800 rotors):
The calipers are small, yet powerful and paired with the new levers, provide very effective and positive braking action. These were included with the dual control levers, along with the brake hoses and all the little bits and barbs. With a Shimano bleed kit, mineral oil and a few YouTube vids, setup was a snap.
The modulation is better than any brakes I have used and the power is incredible. I can more easily slow down without any risk of mistakenly locking up the wheels, as the feedback is so very predictable and accurate. I like that I approach corners faster, brake with confidence at the last possible moment and know they are going to slow me exactly as much as I want. Working on the brakes, replacing the pads, bleeding, etc… Is very easy and user friendly, at least if you have some mechanical background and/or the knack for it and some patience. I find the system to be much easier to maintain and adjust vs. something like SRAM road or MTB systems.
The rotors are vented and have cooling fins. The interaction between the pads and the rotors is very smooth and quiet. Despite a lot of mountain riding, the pads seem to be holding up very well.
GRX FC-RX820-2 Crankset:
The crankset is essentially the same as the previous version in terms of overall design and look, though is now fitted with 12 spd compatible rings. Crank lengths come in 170, 172.5, 175 and ring combos of 31/48 or 30/46, which, paired with the 11-36 or 11/34 cassette provides a very nice wide range of gearing for most roads and dirt roads.
WH-RX880 Carbon Wheelset:
The RX880 wheels are exceptionally lightweight and that is immediately felt on the ride, especially when accelerating and going uphill. With a shallow 32 mm rim height, they keep the weight down and are low profile enough to be minimally affected by crosswinds. They are tubeless ready, with the appropriate valve and rim tape, so all you need to do is install a tire (up to 50mm wide) and add sealant.
Each wheel has 24 bladed / butted spokes (2.0/1.6/2.0) and are of course standard size through axle. The rear wheel comes in either Microspline (for gravel), or HG spline L2 (for road).
The disc mount is center lock to accommodate 140mm disc brake rotors.
The carbon wheels are not only exceptionally light, but have so far proven to be very smooth riding and durable, having been riding them hard on washboard dirt roads, light trails and they are still very straight and true.
Battery/Wiring: While the levers are completely wireless, the derailleurs require power from an internal battery that is typically mounted in the seatpost/seat tube. I contemplated this option, but as it turns out, I was able to get a battery mount to install in the downtube cargo area, which seemed much more logical and easy, at least in this build. Mounting the battery and routing the wires to the derailleurs proved to be fairly easy on the Trek Checkpoint. While I overall prefer Shimano over SRAM, I do like that their newer options have the battery on the derailleur to make for a completely wireless system (though I will say that the Shimano battery lasts much longer). Trade offs I guess.
Above, I have circled the battery that I mounted low in the downtube, which looks daunting, but was really easy in the end.
Adjustments/App: The Shimano E-Tube app is the control center for the Di2 system, where you sync the levers to the rear derailleur, configure the button controls, shift settings and micro adjustments as needed. You can connect multiple Di2 bicycles here, name them and even add a photo of the bike.
I’ll confess that syncing can be frustrating and time consuming, but fortunately, I do not have to do this often, mostly just when first getting the system set up.
This screen is self explanatory, where you set up your gear ratios.
On this screen, you can assign the buttons in a near infinite amount of configurability. While I tried different setups, I ultimately kept the main lever/button functionality stock, as it made most sense to me.
Battery levels and adjustment stats. Given the challenges to connect, I check in on battery levels on my connected Garmin 1050 (more on that later).
Time spent in each gear. Cool!!
Like mechanical derailleurs, Di2 still needs limit screws set as well as B tension, but once that is set, I honestly had nothing more to do and didn’t want to mess with it and risk interfering with perfection.
Garmin Integration: Setting up Di2 has just been a constant stream of awe and amazement, where I was constantly saying “wait, what? I can actually do X? Y? Z? Yes!!” and integration with my Garmin computer was a major bonus. I love that I can control the unit with the buttons on the hoods to scroll screens (or you can operate lights or set up for other functions). Also, if you happen to have a Garmin Edge 1050, you can activate the bell, which is very convenient on the bike path or when passing other cyclists.
I like having the gear combo as one of my main data fields, which takes the guesswork out of it and having to look down at your cassette. It also rings an alarm to let you know when you are at the high or low limit, or if you are at the point where the front derailleur will auto shift to prevent cross chaining.
More gear detail, but the key here is to keep tabs on battery level.
Performance: This is far and away the best groupset I have ever ridden. Everything about the GRX 2x12 Di2 groupset is so well thought out and performance is absolutely perfect. From the low (no) maintenance accuracy of the shifting, especially the front under demanding circumstances, to the ergonomic comfort of the levers, ease of setup, button configurability, battery life, durability, integration with Garmin (as well as other computers), the clutch on the rear derailleur and the braking ease and confidence. Not to mention how perfect the RX880 wheels complete the group.
Conclusions/Recommendations: Some may question whether it is worth it to upgrade to Di2 and I would say it depends. Mechanical GRX is absolutely amazing as well and perhaps preferable if you are riding very long distance, remote bike packing as to not have to worry about recharging, BUT for just about all other scenarios, I can say with confidence that Di2 is an advantage, it is just a step above for all the reasons I listed above. I highly recommend!
Tester Profile
Jeff Valliere has been around bikes his entire life, as a toddler following his dad to bike races and bike shops, BMX racing as a kid, working in bike shops as a mechanic for 14+ years (10 at U-Bikes in Boulder where he met John) and racing as a professional road cyclist for several years. Jeff no longer races, but still loves to ride as he introduces his daughters to the joys of cycling. In addition to being obsessed with cycling, he runs mountains daily and has been reviewing running shoes/gear/tech for RoadTrailRun since 2015 and for other publications/companies since 2005.
RoadTrailRide Reviews HERE
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