New Ultegra Di2 12 speed technical concerns

[Nick le Rock]

Good day.

I am at my wit's end, and home there is someone in this community who can help me.

I have a road bike that I bought in 2011 with a Shimano 3x10 speed 105 drivetrain.

December 2025 (three months ago) I bought a new bicycle with a Shimano Ultegra 12 speed Di2 (R8100 series) drive train.

Anyone who has experience with this model, please feel free to give me some advice.

Since day one, shifting has been crisp and fast and most gears feel smooth. When I am in the small chainring, however, gears 5 through 8 feel rough, almost like I'm riding on gravel or rough tarmac. It's not the same as chain rub, and all kinds of settings with the E-tube app has failed to fix the problem. It is intermitted in the sense that, if I soft pedal, I don't feel it. When I pedal harder, over 150watts, it starts, and then it might be there for two to three pedal revolutions and gone for one, and back and gone.

One week after I bought the bike, I took it back to the shop and explained my problem. They had the bike for a few hours and gave it back to me and said it was set up. I went home, and the problem was still there. I thought I would give it some time, because maybe the drivetrain had to be 'ridden in' so to speak, to give all the components time to be married. After three months, and about 2000km, the problem persists. 

I took it back to the shop for it's complimentary first service and again mentioned the issue. They serviced the bicycle and re-lubed the free body and the chain. The problem persisted. It was slightly better, but as the chain started to dry, the problem felt worse again. I then treated my chain with hot drip wax and it felt better, but still the problem was not gone. I again contacted the bike shop. This time they replaced the cassette and chain with a new cassette and chain. The problem is still there. 

I have not felt this with my old bicycle with 105. The higher gears, 10 through 12, have some cross chain noise, but this is a different noise to the feeling I get with 5 through 8.

To those of you out there with experience with this drive train, I have two questions:

1. Am I over critical with the new 12 speed? Do they seem a bit more rough due to their close spacing?

2. If I am not going crazy, what else can I try, or suggest to the bike shop? I'm pretty hands-on with my other bicycles and have most of the right tools to try and troubleshoot at home.

Thank you in advance for any information that can help me solve this problem.

[MongooseMan]

11 minutes ago, Nick le Rock said:

Good day.

I am at my wit's end, and home there is someone in this community who can help me.

I have a road bike that I bought in 2011 with a Shimano 3x10 speed 105 drivetrain.

December 2025 (three months ago) I bought a new bicycle with a Shimano Ultegra 12 speed Di2 (R8100 series) drive train.

Anyone who has experience with this model, please feel free to give me some advice.

Since day one, shifting has been crisp and fast and most gears feel smooth. When I am in the small chainring, however, gears 5 through 8 feel rough, almost like I'm riding on gravel or rough tarmac. It's not the same as chain rub, and all kinds of settings with the E-tube app has failed to fix the problem. It is intermitted in the sense that, if I soft pedal, I don't feel it. When I pedal harder, over 150watts, it starts, and then it might be there for two to three pedal revolutions and gone for one, and back and gone.

One week after I bought the bike, I took it back to the shop and explained my problem. They had the bike for a few hours and gave it back to me and said it was set up. I went home, and the problem was still there. I thought I would give it some time, because maybe the drivetrain had to be 'ridden in' so to speak, to give all the components time to be married. After three months, and about 2000km, the problem persists. 

I took it back to the shop for it's complimentary first service and again mentioned the issue. They serviced the bicycle and re-lubed the free body and the chain. The problem persisted. It was slightly better, but as the chain started to dry, the problem felt worse again. I then treated my chain with hot drip wax and it felt better, but still the problem was not gone. I again contacted the bike shop. This time they replaced the cassette and chain with a new cassette and chain. The problem is still there. 

I have not felt this with my old bicycle with 105. The higher gears, 10 through 12, have some cross chain noise, but this is a different noise to the feeling I get with 5 through 8.

To those of you out there with experience with this drive train, I have two questions:

1. Am I over critical with the new 12 speed? Do they seem a bit more rough due to their close spacing?

2. If I am not going crazy, what else can I try, or suggest to the bike shop? I'm pretty hands-on with my other bicycles and have most of the right tools to try and troubleshoot at home.

Thank you in advance for any information that can help me solve this problem.

Have had that before, freehub needed a service. After properly cleaning and re-greasing my drivetrain is back to silky smooth in every gear.

[Nick le Rock]

1 hour ago, MongooseMan said:

Have had that before, freehub needed a service. After properly cleaning and re-greasing my drivetrain is back to silky smooth in every gear.

Thanks @MongooseMan

Would you mind elaborating? Did you service it yourself or did a shop service it for you? If you did it yourself, what all did you do? Was this also a 12 speed?

Thank you for taking the time to reply to my post.

[Mongoose!]

 

4 hours ago, Nick le Rock said:

Thanks @MongooseMan

Would you mind elaborating? Did you service it yourself or did a shop service it for you? If you did it yourself, what all did you do? Was this also a 12 speed?

Thank you for taking the time to reply to my post.

If you can, maybe try a different wheel set with your own cassette and rotor fitted.

[MongooseMan]

7 hours ago, Nick le Rock said:

Thanks @MongooseMan

Would you mind elaborating? Did you service it yourself or did a shop service it for you? If you did it yourself, what all did you do? Was this also a 12 speed?

Thank you for taking the time to reply to my post.

I did it myself, but I’m fairly comfortable with the innards of ratchet freehub. If you’re not, take it to the shop and ask them to clean and regrease the ratchets.

 

Yes, was also a 12 speed. Mine would complain certain gears (felt like sand in the system), and changing gear would sometimes fix it.

[Barry]

Maybe you should ask your LBS to check the hanger alignment. If it feels rough through gears 5 to 8, particularly around the mid-cassette, then the hanger might be the issue.

[Nick le Rock]

22 minutes ago, Barry said:

Maybe you should ask your LBS to check the hanger alignment. If it feels rough through gears 5 to 8, particularly around the mid-cassette, then the hanger might be the issue.

Thank you Barry. 

This is actually the one thing I explicitly asked them to check, and they assured me, at three occaaions, that it was straight. However, this is also the answer that ChatGTP and CoPilot gave me, so maybe I should ask a different bike shop to check the allignment for me, while I wait.

[Hilton.]

12 hours ago, MongooseMan said:

Have had that before, freehub needed a service. After properly cleaning and re-greasing my drivetrain is back to silky smooth in every gear.

I agree with this - it was also my assumption about the problem.

Get your bike shop to check the rear hub internals. It sounds like the freehub bearings might be done, or just need cleaning and regreasing.

[splat]

21 minutes ago, Nick le Rock said:

Thank you Barry. 

This is actually the one thing I explicitly asked them to check, and they assured me, at three occaaions, that it was straight. However, this is also the answer that ChatGTP and CoPilot gave me, so maybe I should ask a different bike shop to check the allignment for me, while I wait.

I was about to say that it sounds like its time for a 2nd opinion at a different bike shop.

It doesn't sound like a Shimano Di2 specific problem.
I doubt that its as simple as a clean or dirty chain.
And a dodgy freehub would probably give issues everywhere, not just in a few gears on your small chainring.
Hanger alignment sounds the most probable cause.

Keen to hear what transpires.

[Nick le Rock]

30 minutes ago, splat said:

I was about to say that it sounds like its time for a 2nd opinion at a different bike shop.

It doesn't sound like a Shimano Di2 specific problem.
I doubt that its as simple as a clean or dirty chain.
And a dodgy freehub would probably give issues everywhere, not just in a few gears on your small chainring.
Hanger alignment sounds the most probable cause.

Keen to hear what transpires.

Thank you.

I will get to another shop in the next few days and ask them to check, and then get back to the group.

Is it worth investing in a ParkTool deraileur hanger alignment tool, or is it something that is needed seldom by riders.

[Barry]

Have you made midrange micro adjustments from gear 5 or 6 when going through all the settings in the app?

[Nick le Rock]

I have only done the suggested RD setting of Shimano, in other words, select gear 5, adjust in the direction of 4 until it rubs, and then back it off 5 to 7 clicks.

[Barry]

 

[Barry]

1 hour ago, Nick le Rock said:

I have only done the suggested RD setting of Shimano, in other words, select gear 5, adjust in the direction of 4 until it rubs, and then back it off 5 to 7 clicks.

After the rub on gear 4 try backing it off 4x then test then 5x and test shouldn't need to go 6 or 7 as 5 should be center.  Do you have any crank spacer on the drive side throwing chain line out? 

[Nick le Rock]

16 minutes ago, Barry said:

After the rub on gear 4 try backing it off 4x then test then 5x and test shouldn't need to go 6 or 7 as 5 should be center.  Do you have any crank spacer on the drive side throwing chain line out? 

I have done everything in the video. Thanks for suggesting it. I have tried backing 4x, 5x, 6x, 7x, all with no change.

I attach some photos of the components of the BB and spacers.

[Nick le Rock]

A quick update, for thise interested. 

I have gotten an appointment with my LBS to check my RD hanger's alignment. With CTCT around the corner, they are very busy, so I can only go on Thursday, but after that I will report back here.