Shimano Ultegra R8170 Di2 Disc In-Depth Review

Introduction

I’m sure there are lots of cyclists out there with older groupsets wondering if the new Ultegra R8170 12 speed di2 disc groupset is worth changing to. Hopefully this detailed in-depth review will help you. There’s quite a bit to cover, so get yourself a coffee and let’s begin.

Firstly, you need to remember that the ultimate groupset will be different for every person. It will depend on the features, performance, price, appearance etc. that YOU desire. This article has been written based on MY experiences and preferences. If your opinions a different to mine, that is PERFECTLY OK! I want you to enjoy your riding and having the right equipment to suit you is a major part of that equation. In this review I will be discussing a range of controversial cycling topics like;

• Mechanical vs electronic shifting.
• Rim brakes vs disc brakes.
• Do we really need 12 gears on a road bike?

My experience riding road bikes includes mechanical shifting, electronic shifting (di2), rim & disc brakes. The aim of this review is to provide you with an informed and balanced opinion based on my experiences. For any groupset to deliver it’s maximum performance, it needs to be installed and adjusted correctly on an aligned rear derailleur hanger and in the case of mechanical groupsets, the cable routing path on the frame is also very important and pre-determined by the frame manufacturer. A poor cable routing path will affect the quality of your mechanical shifting, but will not be a problem for electronic shifting.

Let’s start with me saying I believe the Ultegra R8170 groupset offers the BEST shifting and braking performance of ANY previous Shimano groupset!

According to Shimano, Ultegra R8100 groupsets provide the SAME performance as the new Dura-Ace R9200 groupsets. The Dura-Ace R9200 groupsets are simply lighter and in my opinion, better looking with the gloss black finish. But the Dura-Ace groupsets also costs about 40% more than Ultegra which is hard to justify when there are no performance differences (they even share the same electric motors). Having said that, if you’ve got deep pockets and want to buy the new Dura-Ace groupset, then you should! I would have preferred it for the weight savings, appearance and just to have Shimano’s best!

Whilst I believe this new Ultegra R8170 groupset offers better shifting and braking performance, there are some negatives which I will discuss throughout this article. In addition, I purchased this groupset with my own money so the review is NOT influenced by any affiliations or sponsorships.

Shifting Performance

Advantages of electronic shifting (Di2) over mechanical shifting:

• No need to replace shift cables (inner and outer housings).
• No need to periodically adjust shift cable tension to keep shifting accurate. This is great for riders that don’t want to fiddle with cable adjustments (ie. most people).
• Awkward cable routing angles have no effect on shifting performance.
• Front derailleur automatically trims to give clearance in any gear combination (even in all cross chain angles).
• Change multiple gears either UP or DOWN down the cassette whilst holding down a shift button.
• Change multiple gears whilst braking, this is one of my new favorite features.
• The di2 system can be synced to a Garmin (or similar GPS) to view on the display di2 info such as;
  • Live display of current gears in use.
  • Number of gear changes on each ride.
• When using the Shimano app, you can view stats like % of riding time in each gear.
• Very little effort to shift gears by pressing or holding a button.
• Very accurate gear shifts, even under pedaling loads.
• Synchro & Semi-Synchro shifting options – I don’t use them.
• Small time saving building a bike with di2, particularly with the new semi-wireless system.
• Micro adjustments can be made on di2 systems to ensure even better shifting accuracy.

That’s quite an extensive list of advantages. You can decide which are relevant to you. Now let’s also look at the disadvantages.

Disadvantages of electronic shifting (di2) over mechanical shifting:

• Previous di2 groupsets cost a lot more to buy than the mechanical equivalent. Interestingly, Shimano no longer offer 12 speed mechanical shift Dura-Ace or Ultegra groupset.
• Is di2 less durable & reliable because of the electronics, motors, switches & batteries?
• Higher cost of replacing electronic components vs mechanical components.
• Battery charging (and coin cell battery replacement for wireless shifters).
• Firmware updates.
• Sometimes it can be hard to notice a shift button press.
• More susceptible to water ingress or contamination?
• Malfunction diagnosis may involve a PC with Shimano software.
• Requires more technical knowledge in terms of button presses to change settings/modes/functions. Optionally connecting it to the Shimano app or your bike computer. Setting shift preferences etc.
• If the rear derailleur goes into crash mode, you need to know the steps to restore normal operation.
• Semi-wireless system has the possibility of wifi interference or a breakdown of communication between the shifters and rear derailleur. Shimano advise the wireless system uses the popular 2.4 Ghz frequency.

I realise that some of these disadvantages may be considered a deal breaker for some riders, but there is a lot more to be discussed, so please continue reading to get ensure you have the full picture.

Improvements of Ultegra 8100 over previous Shimano di2 Groupsets:

• Semi-Wireless setup makes it easier to build the bike, slightly lighter than a fully cabled setup.
• Hyperglide+ cassette provides smoother down shifts under pedaling load.
• 12 speed cassette offers more range with smoother increments between gears.
• Rear derailleur features built-in wireless protocols to sync with Shimano app and GPS units so no wireless adapter required with prior di2 groupsets.
• Faster shifting performance with new motors for both front and rear derailleurs.
• Thinner cables.
• New battery.
• Rear derailleur features a longer cage to suit a larger 34t rear sprocket.

It’s now 12 speed. How many gears do you need on a road bike?

This is another contentious topic among many cyclists. I like to have as many gears as I can, but there are conditions. If you want to know more, read my article on this topic.

Typically, the advantage of having more gears is for a wider range and/or reduced jumps between gears, but it needs to suit your requirements. Also this new Hyperglide+ cassette provides smoother shifting under load than the 11 speed groups, but it is only a small improvement in my opinion. I still prefer to back off the power a bit when changing sprockets at the rear. I believe it’s just better for the longevity of your parts.

According to Shimano’s website, the new 12 speed 11t-34t cassette (345 grams) is only 10 grams heavier than the older 11 speed Ultegra 11-34t cassette (335 grams).

Disadvantages of New Ultegra 12 speed cassettes vs Shimano 11 speed cassettes:

• FEWER cassette options (only 11t-30t & 11t-34t for 12 speed), many more options for 11 speed groupsets which means on 11 speed drivetrains you can have more gears you use regularly and swap cassettes for special rides in different terrain.
• Higher cost.
• Will they be as durable as the 11 speed cassettes?
• Will the new 12 speed chain (picture below) last as long as the 11 speed chain?

Braking Performance

For me, I found the feel of the 105 hydraulic disc brake levers a bit too soft with less initial bite. Whilst you could brake with less effort, I had to pull the lever more to get the same amount stopping power as the rim brake levers. Additionally, I found the 105 gear shift levers would contact my fingers when stopping in the drops (even with reach adjustment fully out). Unfortunately, there was no free stroke adjustment on those 105 shifters. Perhaps that may have allowed me to firm up the levers a bit. Also the front rotor was only 140mm diameter.

So I was eager to see if the new Servo Wave braking technology included in Ultegra R8170 would feel better. Quite simply YES, these new Ultegra R8170 disc brakes feel MUCH better to me, offering more initial stopping power with less lever pull than the old 105 hydraulic disc brakes. In every respect they feel superior to my rim brakes. But that in itself is not the main reason I changed to disc brakes. The braking performance of disc brakes in the wet is far superior to rim brakes. But disc brakes are certainly not perfect. Read my article comparing rim brakes versus disc brakes on road bikes.

Weight

Depending on a number of factors, the weight of a groupset will vary from bike to bike. Things like crank length, chain ring sizes, cassette size, length of the chain, disc rotor sizes and hydraulic brake cable lengths will all effect the total weight of the groupset. For this comparison, I am going to quote weights reported from various online reviews. When launched, Ultegra 8170 groupset was quoted as weighing about 2716 grams, being about 278 grams heavier than Dura-Ace R9200 (2438 grams) excluding wheels. The biggest single component weight difference between the Dura-Ace and Ultegra was the cassette (Dura-Ace is 74 grams lighter than Ultegra). Nice weight saving, but which is more durable?

I would have liked Ultegra R8170 to be LIGHTER, but NOT at the expense of durability. Ultegra has a reputation for being a robust groupset. Depending on which reviews you read, the new 12 speed Ultegra 8170 (2716 grams) is about 89 grams heavier than the previous 11 speed Ultegra R8070 groupset (2627 grams). A small amount of weight can be attributed to the 12 speed cassette (with an extra cog) and a longer rear derailleur cage. It would have been nice if they had matched the weight of the previous version.

Since the addition of disc brakes, road groupsets have become heavier. It wasn’t that long ago that professional riders using di2 rim brake groupsets were adding extra weight to their bikes to meet the UCI minimum weight of 6.8kg, but since the move to disc brakes, this is typically not the case anymore. If you are very weight conscious, then a rim brake groupset would be a better option. Whilst we all want a lightweight bike, I have read studies that for each 1 kg of weight carried up a climb, only about an extra 3 watts of power is required, which is quite surprising. Of course, many of us could lower our overall system weight just by shedding a few kilograms. Whilst you might improve your performances, it doesn’t give you the satisfaction of lifting a light road bike off the ground!

Durability & Reliability

Shimano has been manufacturing di2 groupsets for many years now. I believe this is the 4th generation. Over the years, di2 groupsets have proven to be reliable and durable. But we all know that electronics, buttons and batteries don’t last forever. I doubt the electrical parts of this groupset would last as long as a well maintained mechanical groupset.

My 2014 Dura-Ace 9000 mechanical groupset has completed over 60,000kms (in 9 years) without replacing derailleurs or shifters. I did have to clean and lube the shifter internals once (when it started ghost shifting), but it was a quick and simple job and once completed, the shifting was perfect again.

Typically Shimano tend to release a new groupset every 3-4 years. Compatibility is often maintained across several model releases, so you should be able to buy replacement or upgraded compatible di2 parts for at least 6-8 years. I guess the real question becomes, how long do you want to keep the bike? If you are going to sell it or swap groupsets within 8 years, there should be no issue getting spare parts, but after that time, it will become more difficult to get NEW matching/compatible parts, however this is similar for Shimano’s mechanical groupsets as well.

How Long Do Di2 Shift Buttons Last?

I rode 65kms over fairly flat terrain the other day and according to my Garmin, I changed gears 300 times on the rear derailleur which is approx 150 button presses for each shifter (up & down). I was surprised by that high figure, but it’s my normal riding style and I used my Dura-Ace 9000 mechanical shifting groupset the very same way. So on average, I am pressing each shift button 2.3 times per kilometer. If I plan to ride 50,000kms on this bike, I wonder if each shift button will work for 115,000 presses? I’m pretty sure the battery will need replacing within 6-8 years of use. In contrast, riding 50,000 kms on my mechanical shifting road bike, I changed the shift cables & housings about 4-5 times (roughly every 10,000 kms) which is time consuming on an internally routed frame. Now at over 60,000 kms, shifting still works perfectly.

Price & Value

According to one of the Ultegra R8170 groupset release reviews in 2022, the launch price for Ultegra R8170 was GBP 2399, GBP 400 more expensive than the previous version Ultegra R8070, but at time of writing (Sept 2023) worldwide supply has increased and this groupset can be bought a lot cheaper than the original launch price.

Worldwide pricing of bicycles and components has increased considerably the past few years, particularly after Covid-19 pandemic. Value is always a matter of perspective. Compared to Dura-Ace R9270, Ultegra R8170 is fantastic value considering the performance is identical and weight difference is not massive, however there are cheaper groupsets out there if you don’t need Shimano’s premium offerings. What components best meet your requirements and budget? How much extra are you willing to spend to enhance your level of riding enjoyment? What upgrades will give you real improvements? Is your bicycle just a tool or is riding your passion?

Wireless vs Fully Cabled di2 Setup

What are the benefits of Shimano’s semi wireless di2 vs the original fully cabled di2?

1. Small weight saving by not requiring cables from shifters to battery or a junction box, but it costs more than it’s fully cabled predecessor.
2. Faster, simpler bike build.
3. A few less cables to possibly rattle inside the frame.

But there are some negatives as well:

1. 2 new coin cell batteries for you to monitor & replace. (A bike computer can help monitor battery life by displaying battery % remaining).
2. The internal battery has about 50% SHORTER run time when using wireless shifter setup.
3. The system could be susceptible to radio interference? It operates on popular 2.4 ghz frequency.
4. You cannot update the firmware for the shifters wirelessly, you need to temporarily connect di2 cables between the battery and each shifter.

Considering all these things, I chose to have my shifters FULLY CABLED rather than using the new semi-wireless setup. I preferred to have the advantages of 50% longer battery life, no hassles doing firmware updates or having to monitor & change batteries in the shifters. Once the shifters are cabled to the internal di2 battery, you can remove the coin cell batteries from the shifters. Even when fully cabled, the di2 system still communicates wirelessly with your bike computer and related phone apps via the wireless functionality built into the rear derailleur.

I had to buy a few extra cables and a junction box, but it’s a small price to pay for the advantages. I’m currently riding about 170km a week. With the shifters cabled to the battery, my di2 battery was still at 15% capacity after riding 2,200 kms. For me that’s about 3 months riding per charge. FYI: The Garmin 540 bike computer will give you battery low warnings from 20%, well before you will run flat.

Ergonomics

Comparison of Shifters from Earlier Shimano Groupsets

I thought it would be interesting to add a picture (below) to compare road shifters from earlier Shimano groupsets to the new Ultegra R-8170 di2 shifter.

• The Dura-Ace ST-9001 for 11 speed mechanical shifting & rim brakes. It is super comfortable everywhere, you don’t feel the mechanisms under the top of the brake lever. It doesn’t rattle over bumps.
  
• The 105 ST-R7020 for 11 speed mechanical shifting & hydraulic disc brakes. It is comfortable on top with plenty to grip, but you can feel the metal mechanism on your fingers as seen under the top of the brake lever. Interesting to note, according to a GCN comparison, the 105 shifter is almost indistinguishable in feel and performance to the Dura-Ace version. Also, I found it rattles over bumps which is a bit annoying if the rest of the bike is quiet. Based on this experience, if you are thinking of buying a Shimano groupset with hydraulic disc brakes, I would recommend you buy the di2 version rather than mechanical shifting to solve the 2 gripes just mentioned.
  
• The Ultegra ST-R8170 for 12 speed di2 & hydraulic disc brakes. It is also super comfortable everywhere. As you can see there are NO metal mechanisms under the top of the brake lever and it doesn’t rattle over bumps. I believe there is a slightly longer reach on these hoods which may increase the reach by 5 to 10mm.

Appearance

Overall, I think the matt black Ultegra R8170 groupset is a very safe option and will suit most bikes, but it is a bit plain for me. I would MUCH prefer the gloss black finish of the Dura-Ace R9270 groupset, but wasn’t willing to pay more money for it. Also, if you are buying a complete bike fitted with Dura-Ace R9270, typically the frame, wheels and other parts will be higher cost also, adding to the extra expense of the Dura-Ace groupset. So the price for the Dura-Ace bike will be considerably higher than the Ultegra model.

One other cosmetic issue I don’t like on these newer road groupsets is the long cage rear derailleur which looks like it belongs on a mountain bike rather than a road bike. I understand it is required for you to use the low gears (30t or 34t sprockets on the rear cassette) but as mentioned earlier, I don’t really need those gears for my normal riding. Standard road bike gearing has certainly changed over the years.

Drivetrain Noise

My Ultegra R8170 groupset is quiet in most gear combinations on my 52-36t crankset with 11-30t cassette. But it isn’t as quiet as my earlier Dura Ace 9000 mechanical groupset in all gear combinations. When the rear derailleur is setup to Shimano’s specifications provided in their dealer manual ie . rear derailleur B-Tension screw is set with a 14mm gap between largest sprocket and guide pulley. Drivetrain chain noise is more noticeable riding the 52t chain ring and 14t or 13t sprocket combinations. If you change the setting of the B-Tension screw (in or out from this setting), the chain noise comes from different sprockets of the cassette, so I suspect this noise is due to a combination of the new cassette teeth profiles and/or the longer cage design of the rear derailleur. When testing, the chain is clean and well lubricated, shift indexing is perfect, the cassette and rear derailleur hanger is aligned correctly and frame chain stay meets Shimano’s 410mm recommended minimum length. I would be interested to hear what Shimano’s engineers have to say.

I don’t hear the motor in the rear derailleur, but you can hear the motor in the front derailleur for a second or so as the gear change is very quick. The ‘click’ sound of pressing the gear shifters is also fairly subtle, sometimes you can’t hear it with wind and road noise, but you will usually hear the chain shifting gears on the rear cassette (or resistance feedback from the pedals ie. moving to harder/easier gear).

Something to Consider: Road bikes with disc brakes require a wider rear triangle frame spacing of 135mm O.L.D. (over locknut dimension). This is 5mm wider than rim brake frame spacing of 130mm O.L.D, so the rear cassette was subsequently moved 2.5mm further out from the center of the frame. This in turn affects the chain line slightly as Shimano didn’t move the chain rings out by the same amount. As such, you are likely to experience more drivetrain noise on certain cross chain angles. In order to help mitigate this situation, I believe Shimano specified a minimum chain stay length of 410mm for its road disc groupsets. This stated minimum requires the chain stays to be 5mm longer than the typical 405mm chain stay length found on road frames for rim brakes. Shorter chain stays (and overall wheelbase) make the frame more responsive. Interestingly, I have still seen modern road bikes for sale (fitted with Shimano disc groupsets) that have chain stay lengths shorter than the Shimano’s 410mm recommendation. Some of this is due to those same frames being equipped with SRAM and Campagnolo groupsets that have different designs & chain lines and I suspect some frame manufacturers may not be willing to sacrifice performance aspects of their geometry by increasing chain stay length to 410 mm.

Shimano road disc groupsets still work OK on bikes with 405mm chain stays. I a different bike with this configuration, but I find the drivetrain is noisier on cross chain angles with a slightly more acute chain line.

What about Frame Spacing for Rear Wheel 142mm Thru Axle Standard?

The rear wheel 142mm thru axle standard still only requires a 135mm rear frame spacing because 3.5mm on each end of the rear wheel hub SLOTS INTO the frame chain stays, therefore 7mm is deducted from the 142mm to match 135mm O.L.D. spacing. Nice to see some standardization here.

Shimano Shadow Rear Derailleur Design Discussed

Shimano moved to a Shadow rear derailleur design with the 2017 release of the second generation 11 speed groupsets (Dura-Ace 9100 / Ultegra 8000 / 105 – 7000). The concept of this design was to give the rear derailleur a super low profile thereby reducing the width of the rear derailleur by 12 mm as pictured below.

Shimano’s website says the design is intended to prevent the derailleur hitting the chain stay in rough riding conditions for smooth and silent performance. Other reviews have stated the rear derailleur is more protected in the event of a crash and requires a much smaller external cable loop from the frame to rear derailleur for mechanical shifting setups.

Shimano have continued with the Shadow rear derailleur in their new 12 speed groupsets. Whilst there are benefits as mentioned, when comparing shadow rear derailleurs with conventional rear derailleurs, I have found that it is more difficult to remove and replace the rear wheel due to;

• The more inboard location of the rear derailleur (getting in the way).
• Increased spring tension in the rear derailleur, making it harder to pull back and out of the way.

Refitting a wheel with a disc rotor also requires a bit more patience, it’s just not as easy as removing and refitting a rim brake wheel with an older (non-shadow) rear derailleur. So expect it to be more fiddly when repairing a flat tyre at the side of the road or fitting your bike to a direct drive indoor trainer.

Summary

Thank you for reading this review. I added a lot of additional topics for people who are thinking of upgrading from different systems. It is important to remember that the information provided is based on my own past experiences, personal preferences and opinions. The review was conducted on equipment I purchased with my own money, so there is no sponsorship or endorsement that would influence my opinions and findings.

If you need a new bike or groupset, then Ultegra R8170 is a fantastic choice. I believe it offers a number of improvements over any Shimano groupset that has preceded it. How much of an improvement will depend on a multitude of factors including your expectations and the quality of the bike build. If you are considering swapping from mechanical shifting & rim brakes to a di2 disc brake groupset, then THIS is the groupset I would recommend. I encourage you to visit a bike shop to test if for yourself before outlaying your hard earned dollars. Hopefully you will find Shimano Ultegra R8170 a worthy successor to anything that has come before it.

Of course I would love Shimano Ultegra R8170 to be lighter & cheaper with more cassette options, but I am very happy with it’s performance, particularly the speed and accuracy of the shifting and improved feel of the disc brakes.

Disclaimer!

Please remember that this information is only to be used as a guide. It does not constitute professional advice.

About Me.

I have been riding and working on my own bikes for many years now. I wanted to share my experiences, knowledge and research with others. My aim is to inspire people to get involved in all aspects of this amazing sport. Cheers.

Comments.

I welcome reader feedback in the comments section. Should you wish to suggest an amendment, please include a note advising the source of your information so that myself and other readers can ascertain the accuracy of your information. Note: Trolling or argumentative comments will be removed as they are counter-productive.