54/36T chainrings with Shimano 105 Di2 / Ultegra?

[cLs_elite]

Hey guys,

How are you? I’m checking some gearing options for my new road bike build (LTK266-D-SL). I didn't find much about this topic online.
I’m considering going with 54/36T chainrings instead of the standard 52/36T setup, paired with an 11–36 cassette in the back.

I live in Switzerland, so there are plenty of climbs — but with my current 52/36T setup, I often spin out on mild downhills, which is why I’d like a bit more top-end.
On the flats, I often end up using the smaller cogs in the back (11T, 12T or 13T), which isn’t great for the chainline either.

My main concern is whether the front derailleur (FD-R7150) can handle the 54T big ring, and also the 18T jump (54–36), since Shimano officially lists a maximum 16T difference — and most specs rate the FD for up to 52T.

I’m wondering if anyone here is running a 54T chainring (or anything with more than a 16T gap) on Shimano, either 105 Di2 or Ultegra Di2 (FD-R8150).

Should I really bother with this, or just stick with the standard setup?

I’d really appreciate any feedback!
Cheers

[jonathanf2]

You'll be pushing beyond the 16t limit and your front shifting might be compromised. I was in a similar situation looking to go with a bigger chainring on one of my road bikes, but I opted to swap out my cassette to an XDR 12 speed cassette. You'll have to swap out your freehub and use something like a KMC X12 chain (Shimano/SRAM cross compatible), but it's an easy way to keep your front 2x chainring intact and get slightly higher top end on the descents and quick speed bursts on the flats. Both my road bikes are using 50-34t and 52-36t chainrings and I settled on using 10-33t on all my wheelsets. I try not to use the 10t often, but it's good to have when you need additional speed. You can either go with SRAM's XDR cassettes or use Goldix XDR cassettes off of AliEx.

[cLs_elite]

You'll be pushing beyond the 16t limit and your front shifting might be compromised. I was in a similar situation looking to go with a bigger chainring on one of my road bikes, but I opted to swap out my cassette to an XDR 12 speed cassette. You'll have to swap out your freehub and use something like a KMC X12 chain (Shimano/SRAM cross compatible), but it's an easy way to keep your front 2x chainring intact and get slightly higher top end on the descents and quick speed bursts on the flats. Both my road bikes are using 50-34t and 52-36t chainrings and I settled on using 10-33t on all my wheelsets. I try not to use the 10t often, but it's good to have when you need additional speed. You can either go with SRAM's XDR cassettes or use Goldix XDR cassettes off of AliEx.

Thanks for the reply; that's definitely an option I should consider. I'm building a new bike and haven't chosen a wheelset yet, so an XDR hub would be possible. The only downside might be chainline alignment, which could result in higher friction and potentially increased wear.

I'm also a bit concerned about the 16T limit—as well the Shimano 105 Di2 maxes out at 52T. But I think with a front derailleur extender, a 54T chainring should be fine. Let's see if anyone has tried it out. Did you find much information online when you were checking for your setup?

[jonathanf2]

Thanks for the reply; that's definitely an option I should consider. I'm building a new bike and haven't chosen a wheelset yet, so an XDR hub would be possible. The only downside might be chainline alignment, which could result in higher friction and potentially increased wear.

I'm also a bit concerned about the 16T limit—as well the Shimano 105 Di2 maxes out at 52T. But I think with a front derailleur extender, a 54T chainring should be fine. Let's see if anyone has tried it out. Did you find much information online when you were checking for your setup?

One advantage I had was running LTwoo ER9, so I was able to fine tune each cog perfectly with the XDR cassette. No issues with FD shifting either since nothing was changed out. That 10t cog really gives an extra kick on the descents and quick burst on the flats when I need it. My road gear cogs are slightly in-board, especially my 11t cog which I find to be more ideal for chain line. Possibly there's more wear, but I have 4 bikes in rotation and all my chains are immersive waxed.

Here's a video detailing their own experience doing the Shimano/SRAM combo:
https://youtu.be/5IdncYZDSrA?si=5g7nT7YJeuGGuI8f

[Da11as]

Have 53/36 with Ultegra Di2, shifting feels the same as 52/36. Front shifting was never an issue for me with Shimano.

[cLs_elite]

Have 53/36 with Ultegra Di2, shifting feels the same as 52/36. Front shifting was never an issue for me with Shimano.

Oh sweet, that’s good to know. Do you know if there’s a big difference between the 105 and Ultegra front derailleurs? Some websites say the Ultegra can handle up to 54T, while others list it as only compatible with 52T. Did you have to use an extender on the FD to make it work?

[Da11as]

Oh sweet, that’s good to know. Do you know if there’s a big difference between the 105 and Ultegra front derailleurs? Some websites say the Ultegra can handle up to 54T, while others list it as only compatible with 52T. Did you have to use an extender on the FD to make it work?

Zero mods have been made. As far as I know, Shimano 105 uses derailleur design from previous generation Di2, whereas Ultegra is newer one. Regardless, I don't see why it won't take 53T chainring and I've seen plenty of Ultegra builds with 56T chainrings without complaints on user's end.

[h0ldb88r]

FWIW I have done a 52/34 before and shifting was fine, thought slightly slow in shifting between the rings.

[cLs_elite]

So just for your information, since I did not find much online about this topic regarding larger chainring setups with a difference of 16+ teeth:

I went with Ultegra Di2 and a 54/36T chainring combo. Shifting works really well. I cannot directly compare it to a 52/36 setup, as I had mechanical Ultegra on my old bike and I am also using off-brand components (casette, chain, chainrings).

I am happy with the setup and would recommend it to anyone considering a bigger chainring.

Note: I am using an extender on the front derailleur.

[alfiomotrambo]

I’m actually running 52/36 at the moment and was just wondering the same thing about going a bit bigger on the big ring.
What extender did you get? Found this on Alix https://it.aliexpress.com/item/1005009736656781.html

[cLs_elite]

Yeah, this one should work.
I bought this adapter 2x times already and no issue:
https://de.aliexpress.com/item/1005008842587068.html