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Shimano 105 Di2 or Shimano Ultegra Di2

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Shimano 105 Di2 or Shimano Ultegra Di2

Old 08-03-23, 03:53 AM
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Shimano 105 Di2 or Shimano Ultegra Di2

Hi everyone,
I'm currently looking out for a new bike. My bike store gave me an offer with the Ultegra Di2. I father (he have a 105) looked at the configuration and tried me to convice me to take the 105 Di2 instead of the Ultegra Di2, because he has a friend in a bike club and everyone who has an Ultegra there complains that they always have problems with it because it bends or otherwise breaks. However, I'm also in a bike club and that's not the case for me. He justifies the bending by saying that it's like the 105. So the same material, but less of the material and the circuit is therefore not as stable and constantly bends. What do you say to that? Would you rather go with the 105 Di2 or the Ultegra Di2?

Thanks in advanced
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Old 08-03-23, 06:10 AM
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What 'bends'???
I've not seen anything 'bend' on the Ultegra Di2 grouppo nor on the 105 for that matter.
I installed the 105 Di2 on my Aethos several months ago and am very happy with it. I've participated in several races, including last weeks 50 mile race which was in torrential downpours for the entire event and the grouppo never glitched once.
I'v'e also built two bike with Ultegra Di2 and neither has experience any problems at all...nothing 'bends'...
It's about cost and needs imo...105 is less expensive but the internals are all the same...105 uses a longer cage on the rear der so it will take a wider range cassette if that is a need or desire...105 doesn't have the buttons on top of the shifter, Ultegra does.
Both systems are fully configurable for shifting and I especially love the ability to tweak the rear der position for every gear on the cassette.
I use the Ultegra cassette 11-30 because I like the hyperglide+ chamfering/etc. I do feel it shifts a bit more smoothly than the 105 cassette. The 'B' limit screw is at its limit but it works great.
I use a 105 compact crankset
I use a dura ace chain which I immerse in Silca Super Secret wax making for a very smooth and quiet drivetrain.
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Old 08-03-23, 06:33 AM
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I have not heard any of this. I'd go with Ultegra if I was building a bike, particularly if I planned to race.
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Old 08-03-23, 07:26 AM
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Ultegra is quite a bit lighter. 105 performs just about as well as Ultegra for a lot less money. Weight might matter if you are competing with others. But it's not going to make you fast.

Consider whose money is buying the bike.
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Old 08-03-23, 10:16 AM
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although i have Ultegra i would be happy with 105. i am very skeptical that Ultegra is bending.
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Old 08-03-23, 10:17 AM
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Originally Posted by Iride01
Ultegra is quite a bit lighter. 105 performs just about as well as Ultegra for a lot less money. Weight might matter if you are competing with others. But it's not going to make you fast.

Consider whose money is buying the bike.
About 370g lighter. It's not going to matter in anything but mountain TTs.
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Old 08-03-23, 11:58 AM
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Originally Posted by lupo68288
...because it bends or otherwise breaks.
This is not correct.
Ultegra is very durable.
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Old 08-03-23, 01:38 PM
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I have bikes with both the Ultegra 12-speed Di2 and 105 12-speed Di2. I've had the Ultegra group for about on the one for a year with absolutely no problems. I got another bike with the 105 Di2 about a month ago, and find that from a riding perspective it is virtually indistinguishable from Ultegra. The main difference is that the 105 does not have all of the extra button features that the Ultegra has (screen scrolling on the computer for example) and the 105 has physical limit screws instead of electronic hi/low limit settings. Shifting performance is virtually the same on both. I've had no durability issues with the Ultegra bike.
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Old 08-03-23, 01:42 PM
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Originally Posted by PeteHski
About 370g lighter. It's not going to matter in anything but mountain TTs.
...and lifting your bike on to the rack after the race.

...and impressing your friends at the coffee shop when they pick up your bike to see how light it is.
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Old 08-03-23, 03:27 PM
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If budget allows, go Ultegra Di2. Just because.

Will it shift better, last longer, and make you faster than 105 Di2? Probably not, but who cares. It's slightly "better" tech with a couple of additional features (which may or may not matter to you).


Originally Posted by Eric F
...and lifting your bike on to the rack after the race.
Haha, word! The struggle is real... 😁
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Old 08-03-23, 07:08 PM
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Do you guys even internet? How is it possible that everyone acts surprised that there are reports of Ultegra cranks breaking and bending?
Start here:
https://www.instagram.com/thanksshimano/?hl=en
There are a ton of pictures and stories of these glued-together cranks breaking:



Bu to answer the OP's question- the 105 does not have this kind of problem because the 105 crankset is not glued together.
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Old 08-03-23, 07:38 PM
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Originally Posted by icemilkcoffee
Do you guys even internet? How is it possible that everyone acts surprised that there are reports of Ultegra cranks breaking and bending?
Start here:
https://www.instagram.com/thanksshimano/?hl=en
There are a ton of pictures and stories of these glued-together cranks breaking:



Bu to answer the OP's question- the 105 does not have this kind of problem because the 105 crankset is not glued together.
You are correct...I did not even think of this problem when reading the post. I thought about the shifting components.
The op should have been more specific I guess.
This is a problem but I wonder if it is a failed manufacturing lot rather than a design flaw? Don't know the answer but I do know the two Di2 Ultegra 12 speed bikes I've built have not had this problem...thus far...with the cranks and both riders are pretty big people...180lbs or so...
Good call on pointing this out.
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Old 08-03-23, 07:52 PM
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105 offers wider gear range than ultegra, I believe, in case that matters
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Old 08-03-23, 09:01 PM
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Originally Posted by Kai Winters
What 'bends'???
...
Both systems are fully configurable for shifting and I especially love the ability to tweak the rear der position for every gear on the cassette.
...
This is off topic, but I recently got a bike with Ultegra Di2 and I couldn't find that I could tweak the position for each gear. I was only using the app though. I'd appreciate a quick explanation how this is done.
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Old 08-04-23, 04:36 AM
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Some of those broken cranks are Dura-Ace and some of those photos are not cranks..... but even so I would ask, what did the rider do to cause that damage? If those cranks were breaking in normal use,I'd think we'd be hearing a lot more about it ... and seeing recalls.

Probably the people saying they have heard about Ultegra breaking ... heard it from this one site, in a big circular self-reference. If someone can show me four or five other sites that discuss this phenomenon Not referencing this site ... I mean, just because it is the internet doesn't mean that we shouldn't use critical thinking and do proper research.

I cannot count how many times I have seen two dozen news reports, all based on rewrites of the same single report, and people say, "Well, it is on two dozen news sites," like that means it is true.

Where are the recalls and lawsuits?
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Old 08-04-23, 06:05 AM
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Originally Posted by Mtracer
This is off topic, but I recently got a bike with Ultegra Di2 and I couldn't find that I could tweak the position for each gear. I was only using the app though. I'd appreciate a quick explanation how this is done.
I use the Etube app to do this for my 105 Di2 12 speed system.
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Old 08-04-23, 06:17 AM
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I've read some of the same reports regarding the broken cranks.
It could be a manufacturing lot where a defect is the cause and it was missed by QC rather than all the cranks ever made of this model.
It is also a possibility of a mix of causes...I've seen people braking a crank arm during a ride/race back in the '90's when they were solid aluminum...generally the person generated a lot of torque/load on the arm and there was a weakness in the metal resulting in the break.
I'm 142 lbs and never broke a crank arm and aren't likely to but a heavier person with a lot of power may do so which may not be considered a manufacturing defect per se but due to size/power/etc of the person on that particular crank.
There is a min/max tolerance value when performing physical tests on anything...if it meets the min value it is passed...also QC people test a percentage of parts, not every part, and if that percentage passes it is approved and moves along, if it fails then more are tested which may result in a failed lot then a manager and/or engineer is called in to evaluate the failed value and may approve it depending on a variety of reasons but generally there is always a lot of documentation that goes along in order to maintain tracking...at least it was so in the companies I was involved with as a QC tester/tech.
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Old 08-04-23, 08:14 AM
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Originally Posted by Maelochs
Some of those broken cranks are Dura-Ace and some of those photos are not cranks..... but even so I would ask, what did the rider do to cause that damage? If those cranks were breaking in normal use,I'd think we'd be hearing a lot more about it ... and seeing recalls.

Probably the people saying they have heard about Ultegra breaking ... heard it from this one site, in a big circular self-reference. If someone can show me four or five other sites that discuss this phenomenon Not referencing this site ... I mean, just because it is the internet doesn't mean that we shouldn't use critical thinking and do proper research.

I cannot count how many times I have seen two dozen news reports, all based on rewrites of the same single report, and people say, "Well, it is on two dozen news sites," like that means it is true.

Where are the recalls and lawsuits?
Been covered by some youtuber's -

Pretty good synopsis there. Corrosion, moisture ingress...

A bit more annoying (but I love this guy)

Last edited by Jughed; 08-04-23 at 08:30 AM.
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Old 08-04-23, 10:43 AM
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Originally Posted by Kai Winters
I use the Etube app to do this for my 105 Di2 12 speed system.
I use the Etube app too, but I've not seen any way to do this. I can select the different gears, but whatever offset I set one gear to, it changes all of them to that same offset. Is there an option I'm missing somewhere?

Again sorry for being off topic.
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Old 08-04-23, 01:58 PM
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Originally Posted by Jughed
Been covered by some youtuber's -
Why do Shimano cranks keep failing? Analysis. - YouTube

Pretty good synopsis there. Corrosion, moisture ingress...
"I've actually got no statistical data to back this up .... " Gotcha. let me know when you do.

I live in the supposed "Danger Zone" and my Ultegra crank is unbroken, despite me weighing an eighth of a ton.

I'd like to see actual numbers here.

Also, if it were glue separating under heat expansion/moisture intrusion ... why would the crank arms be splitting in half mid-arm, and not splitting laterally? When I look at the photos on the Instagram site, i see all manner of failure but not a lot of lateral separation. (By the way, there are what, 300-odd photos on that Instagram page, and a lot of them are not even cranks. So we are talking about what ... 600 crank failures (because obviously this guy didn't get all of them) over ten years? How many failures per crank sold? Any actual info? No?

I assume anyone who has ever had any sort of issue with an Ultegra or DA front end has posted a pic, even if it was damaged when the bike fell off the rack on the highway heading to an event.

This is the difference between "anecdote" and "data." "A couple of friends and a couple other guys plus some other guy I heard about ... " versus "some precise number of crank failures out of some precise number produced." Is it six, sixteen 16,000? Show me the math.

From the comments on that page: "Over the last 25 years, I've broken 4 Dura Ace cranks. 3 of the 4 have been right in the middle of the threaded pedal hole, going outward to the edges, then abruptly breaking off. I'm always careful not to over torque. Just a bit of pressure at the end to snug up the pedals on the cranks. These breaks have occurred both on the left and right crank arms. One break occurred in the middle of the drive side crank arm, about half way from the pedal to the spider. In all instances, I went down, once breaking a finger. Shimano was always good about replacing the crank sets. I examine mine but can never any cranks. It just happens all of a sudden. I'm 175 lbs. I do ride in very hilly area's in Northern California typically climbing at least 2k feet per ride, always dry weather riding. Back in the day when I was riding a 150 miles a week, Shimano advised me to replace my cranks every 3 years. Doesn't seem like this should be happening but it does. I don't abuse them, just use them. they are definitely a safety hazard. for me anyway. good luck with yours."

So that guy has been suing these "safety hazard" cranks since before they were bonded .... and been breaking them .... and here he is adding his numbers to the total even though they are not relevant. Also, Shimano replaced all of them, he says. Still ... not relevant, but counted as relevant.

Also: "Many years as a shop mechanic in Australia and zero failures through the shop, zero. Worked also with maybe pro teams and only one arm failure with Dockers left crank. Obviously this is happening, but I would be interested in a quick division, about sold divided by the amount failed. Pretty confident the answer will be tiny. Great video and I think you've nailed the reasons. But once again, zero through our store and never even heard of any other stores having issues. Many as we have little humidity"

This is what I mean about anecdote versus data. One person says he broke DA cranks even before they were Hollowtech, and another guy says he worked in a bike shop in the Danger Zone and has never seen this. Does either comment carry weight? Do we only look at the comments that support the theory?

This is not science. We have no idea if the same 1600 people are being cited 16,000 times each or if four out of seven Hollowtech DA or Ultegra cranks break. Interesting video, but absent solid information it is just, "Some guy told a story and I had some thoughts about the story."

I will continue to use Ultegra cranks with confidence, while I wait for further developments.

(I skipped the annoying guy .... if he bugs you .... good enough. If he has Actual Numbers please let me know.)
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Old 08-04-23, 02:21 PM
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Originally Posted by Mtracer
This is off topic, but I recently got a bike with Ultegra Di2 and I couldn't find that I could tweak the position for each gear. I was only using the app though. I'd appreciate a quick explanation how this is done.
Put it in adjust mode (look in the manual). You press the R shift up or down to move the R derailer a millimeter or 2 in either direction as setting adjustment. Itís like tightening or loosening the cable tension on a mechanical system
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Old 08-04-23, 03:16 PM
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Originally Posted by Steve B.
Put it in adjust mode (look in the manual). You press the R shift up or down to move the R derailer a millimeter or 2 in either direction as setting adjustment. Itís like tightening or loosening the cable tension on a mechanical system
My question relates to individually adjusting each gear, not adjusting all the same. I understand how to make the equivalent of a cable tension adjustment that affects all gear positions the same. It was just mentioned earlier in this thread that Di2 allows for individually adjusting each gear, or at least I read it that way. If that can be done, I've not been able to figure out how to do that. Either using the derailleur and shifter buttons, or using the E-Tube app.
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Old 08-04-23, 03:45 PM
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Originally Posted by Mtracer
My question relates to individually adjusting each gear, not adjusting all the same. I understand how to make the equivalent of a cable tension adjustment that affects all gear positions the same. It was just mentioned earlier in this thread that Di2 allows for individually adjusting each gear, or at least I read it that way. If that can be done, I've not been able to figure out how to do that. Either using the derailleur and shifter buttons, or using the E-Tube app.
I have never read of any method of adjusting individual gears, just the method I described of tuning where the chain sits center on a cog, for all the cogs.
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Old 08-04-23, 05:42 PM
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Originally Posted by Maelochs
"I've actually got no statistical data to back this up .... " Gotcha. let me know when you do.

I live in the supposed "Danger Zone" and my Ultegra crank is unbroken, despite me weighing an eighth of a ton.

I'd like to see actual numbers here.

Also, if it were glue separating under heat expansion/moisture intrusion ... why would the crank arms be splitting in half mid-arm, and not splitting laterally? When I look at the photos on the Instagram site, i see all manner of failure but not a lot of lateral separation. (By the way, there are what, 300-odd photos on that Instagram page, and a lot of them are not even cranks. So we are talking about what ... 600 crank failures (because obviously this guy didn't get all of them) over ten years? How many failures per crank sold? Any actual info? No?

I assume anyone who has ever had any sort of issue with an Ultegra or DA front end has posted a pic, even if it was damaged when the bike fell off the rack on the highway heading to an event.

This is the difference between "anecdote" and "data." "A couple of friends and a couple other guys plus some other guy I heard about ... " versus "some precise number of crank failures out of some precise number produced." Is it six, sixteen 16,000? Show me the math.

From the comments on that page: "Over the last 25 years, I've broken 4 Dura Ace cranks. 3 of the 4 have been right in the middle of the threaded pedal hole, going outward to the edges, then abruptly breaking off. I'm always careful not to over torque. Just a bit of pressure at the end to snug up the pedals on the cranks. These breaks have occurred both on the left and right crank arms. One break occurred in the middle of the drive side crank arm, about half way from the pedal to the spider. In all instances, I went down, once breaking a finger. Shimano was always good about replacing the crank sets. I examine mine but can never any cranks. It just happens all of a sudden. I'm 175 lbs. I do ride in very hilly area's in Northern California typically climbing at least 2k feet per ride, always dry weather riding. Back in the day when I was riding a 150 miles a week, Shimano advised me to replace my cranks every 3 years. Doesn't seem like this should be happening but it does. I don't abuse them, just use them. they are definitely a safety hazard. for me anyway. good luck with yours."

So that guy has been suing these "safety hazard" cranks since before they were bonded .... and been breaking them .... and here he is adding his numbers to the total even though they are not relevant. Also, Shimano replaced all of them, he says. Still ... not relevant, but counted as relevant.

Also: "Many years as a shop mechanic in Australia and zero failures through the shop, zero. Worked also with maybe pro teams and only one arm failure with Dockers left crank. Obviously this is happening, but I would be interested in a quick division, about sold divided by the amount failed. Pretty confident the answer will be tiny. Great video and I think you've nailed the reasons. But once again, zero through our store and never even heard of any other stores having issues. Many as we have little humidity"

This is what I mean about anecdote versus data. One person says he broke DA cranks even before they were Hollowtech, and another guy says he worked in a bike shop in the Danger Zone and has never seen this. Does either comment carry weight? Do we only look at the comments that support the theory?

This is not science. We have no idea if the same 1600 people are being cited 16,000 times each or if four out of seven Hollowtech DA or Ultegra cranks break. Interesting video, but absent solid information it is just, "Some guy told a story and I had some thoughts about the story."

I will continue to use Ultegra cranks with confidence, while I wait for further developments.

(I skipped the annoying guy .... if he bugs you .... good enough. If he has Actual Numbers please let me know.)
Those two fellers are aerospace engineers that specialize in composites. They both did a solid root cause analysisÖ

The second annoying feller had his very own set fail, which prompted his analysis of the issue, and led him to find the other failures. And to quote himself, he has the power output of a shrimp.


There is an absolute inherent design flaw mating steel to aluminum with the presence of moisture.

I have a set of dura ace cranks that are showing signs of failure - and I no longer ride them.

Just because we paid a ton of money for a product doesnít mean the product isnít prone to issues.
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Old 08-04-23, 06:44 PM
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Originally Posted by Jughed
Those two fellers are aerospace engineers that specialize in composites. They both did a solid root cause analysisÖ

The second annoying feller had his very own set fail, which prompted his analysis of the issue, and led him to find the other failures. And to quote himself, he has the power output of a shrimp.


There is an absolute inherent design flaw mating steel to aluminum with the presence of moisture.

I have a set of dura ace cranks that are showing signs of failure - and I no longer ride them.

Just because we paid a ton of money for a product doesnít mean the product isnít prone to issues.
Yu seem not to have understood my post.

I am not saying this failure never happens. I am asking how often, and whether anyone can show that it is a significant portion or just occasional iterations of these cranks. How prevalent is it?

As I say, I also have 6800 cranks, live in the Danger Zone, and have Not seen any issues. That no more proves that they never fail, than some number of people posting pics of cranks and other bike parts, prove that Ultegras and DA cranks are largely hazardous.
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