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Swapping out cassettes sizes on a Di2 bike

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Swapping out cassettes sizes on a Di2 bike

Old 06-30-20, 04:15 PM
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roadCruiser76
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Swapping out cassettes sizes on a Di2 bike

OK, so I'm vaguely considering getting a new road bike, one which has di2 and disk brakes. My current road bike has rim brakes and mechanical shifting. However, one thing I like about my existing road bike is the gear ratio. My lowest gear combination is a 36 in the front and a 34 on the cassette. All of the di2 bikes I've seen, however, either have a 34/28 or a 36/30 as their lowest gear combination. I was wondering how involved it would be for my LBS to swap out cassettes on a di2 bike in favor of one with a larger gear. When I had it done on my existing bike I needed to get a new rear derailler. I wouldn't want to have to replace the di2 component just to have a different sized cassette. Any thoughts?

Second question: is it worth getting a new road bike to get electronic shifting and disk brakes? Or are those things overrated?
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Old 06-30-20, 04:42 PM
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Specialized equips Roubaix with Ultegra R8050 with 11-34t rear cassette.

Disc brakes and electronic shifting are both very nice to have.
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Old 06-30-20, 07:20 PM
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The size of the cassette and/or chain rings isn't really a Di2 issue. Di2 however can be programmed to "know" what gears you have on your bike which will allow it to set the shift points for what is known as "synchronized shifting". Don't concern yourself with that right now... just know it's cool

The reason you may or may not need a new rear derailleur typically has to do with the size of the largest cog on the cassette. I *think* that most Shimano short-cage rear road derailleurs top-out at around a 32 tooth cog. If you want bigger than that, you'll need a long cage.

Why kind of bikes are you looking at... pure racing bikes? Bikes that are considered "endurance bikes", like the Trek Domane and Specialized Roubaix come with gearing closer to what you're looking for.

Originally Posted by roadCruiser76 View Post
Second question: is it worth getting a new road bike to get electronic shifting and disk brakes? Or are those things overrated?
Believe-you-me, you'll love both once you get used to them and won't go back. Electronic shifting opens up a whole new world, especially if you buy a decent computer like a Garmin or Wahoo and install the wireless adapter so the Di2 system can talk directly to the computer.
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Old 06-30-20, 07:38 PM
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I have the first gen ultegra 11-speed Di2, with a mid-cage rear derailleur spec-ed for 32T max. I can run a 36T cassette with no problem (just cranked on the B-screw a bit). A 46/30T GRX crank works fine with my Ultegra Di2 front derailleur as well. Shimano is very conservative with its specs.
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Old 06-30-20, 07:46 PM
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The Ultegra R8000 series Di2 RD comes in both short & med. cage styles. Max for the short it 30T & med. is 34T although Shimano is notoriously conservative about this. As long as you get a bike with the med. cage RD you're good to go. A lot of endurance bikes now come with an 11-34T but if it doesn't as long as the RD is a med. cage a good bike shop will swap out to the 11-34T as part of the sale and setup.

The Dura-Ace series R9150 Di2 RD only comes in the short cage style so 34T might be more problematic.

I love Di2 as do most people who have it but there are few who prefer mech. or would rather spend their money differently.
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Old 07-01-20, 09:04 AM
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Originally Posted by PoorInRichfield View Post
The size of the cassette and/or chain rings isn't really a Di2 issue. Di2 however can be programmed to "know" what gears you have on your bike which will allow it to set the shift points for what is known as "synchronized shifting". Don't concern yourself with that right now... just know it's cool

The reason you may or may not need a new rear derailleur typically has to do with the size of the largest cog on the cassette. I *think* that most Shimano short-cage rear road derailleurs top-out at around a 32 tooth cog. If you want bigger than that, you'll need a long cage.

Why kind of bikes are you looking at... pure racing bikes? Bikes that are considered "endurance bikes", like the Trek Domane and Specialized Roubaix come with gearing closer to what you're looking for.



Believe-you-me, you'll love both once you get used to them and won't go back. Electronic shifting opens up a whole new world, especially if you buy a decent computer like a Garmin or Wahoo and install the wireless adapter so the Di2 system can talk directly to the computer.
I'm kind of torn also between a "racing" road bike versus a more "endurance" type one. I'm way too slow to do actual races, but sometimes I do fast group rides with my cycling friends and I'd like to be able to keep up as much as possible. Of course, sometimes I also do "climbing" rides with these same friends where we go up significant grades, so it would be good to have adequate gearing for that as well. Ideally I'd like something that could do both - a "racing" oriented road bike with a good range of gears so I could conquer some 18/19% grades with no problem.

The electronic shifting aspect does seem pretty cool, I must admit!
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Old 07-01-20, 09:05 AM
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Originally Posted by wgscott View Post
I have the first gen ultegra 11-speed Di2, with a mid-cage rear derailleur spec-ed for 32T max. I can run a 36T cassette with no problem (just cranked on the B-screw a bit). A 46/30T GRX crank works fine with my Ultegra Di2 front derailleur as well. Shimano is very conservative with its specs.
Good to know that you can even handle a 36T cassette...
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Old 07-01-20, 09:09 AM
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Originally Posted by August West View Post
The Ultegra R8000 series Di2 RD comes in both short & med. cage styles. Max for the short it 30T & med. is 34T although Shimano is notoriously conservative about this. As long as you get a bike with the med. cage RD you're good to go. A lot of endurance bikes now come with an 11-34T but if it doesn't as long as the RD is a med. cage a good bike shop will swap out to the 11-34T as part of the sale and setup.

The Dura-Ace series R9150 Di2 RD only comes in the short cage style so 34T might be more problematic.

I love Di2 as do most people who have it but there are few who prefer mech. or would rather spend their money differently.
Cool! The ones I'm looking at do say "medium cage". Maybe that's the answer then - get a racing oriented bike and ask the shop to throw on a 34T cassette for me once it comes in. Thanks for the info!
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Old 07-01-20, 09:15 AM
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Originally Posted by roadCruiser76 View Post
I'm kind of torn also between a "racing" road bike versus a more "endurance" type one.
I love my endurance bike. At 46 years of age, I'm just not willing to take the beating of a harsh race bike like I was able to when I was 20.

When you say, "significant grades", are you talking about mountains or hills? I live in the Midwest where there are no mountains. As such, buying a super-light "climbing bike" when most of my rides don't involve extreme climbing doesn't make sense.

If you're interested in an endurance bike that's a bit lighter, the Canyon Endurance CF SL Disc is a little lighter than my 2020 Trek Domane, but not much. It's really hard to make a bike that has a lot of comfort features but still a feather-weight for climbing. If someone knows of a bike that does both well, let us know!
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Old 07-01-20, 09:42 AM
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Originally Posted by PoorInRichfield View Post
I love my endurance bike. At 46 years of age, I'm just not willing to take the beating of a harsh race bike like I was able to when I was 20.

When you say, "significant grades", are you talking about mountains or hills? I live in the Midwest where there are no mountains. As such, buying a super-light "climbing bike" when most of my rides don't involve extreme climbing doesn't make sense.

If you're interested in an endurance bike that's a bit lighter, the Canyon Endurance CF SL Disc is a little lighter than my 2020 Trek Domane, but not much. It's really hard to make a bike that has a lot of comfort features but still a feather-weight for climbing. If someone knows of a bike that does both well, let us know!
For "significant grades", I'm thinking about a local climb called Lamb's Knoll. The grade hits 18-19% in a few sections and it's just impossible to keep an adequate cadence without good gearing. The total elevation for the climb is about 1000 feet. 1000 feet is pretty typical around here for "low mountain" climbs.

I need gearing for a climb like this:


Last edited by roadCruiser76; 07-01-20 at 09:50 AM. Reason: Added picture
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Old 07-01-20, 09:44 AM
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Originally Posted by roadCruiser76 View Post
I'm kind of torn also between a "racing" road bike versus a more "endurance" type one. I'm way too slow to do actual races, ........................
Don't rule out bikes based on the marketing terms. Try them on before you reject them. When you get a new bike, it'll have so many spacers under the stem that it will be outside anything I'd call an aero position or "race fit".

Endurance bikes that I remember being called such back in the 1970's were more for those that wanted to put panniers and racks on their bikes and carrying a load of equipment while on multi-day rides and camping along the way.
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Old 07-01-20, 10:56 AM
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Originally Posted by roadCruiser76 View Post
I'm kind of torn also between a "racing" road bike versus a more "endurance" type one. I'm way too slow to do actual races, but sometimes I do fast group rides with my cycling friends and I'd like to be able to keep up as much as possible. Of course, sometimes I also do "climbing" rides with these same friends where we go up significant grades, so it would be good to have adequate gearing for that as well. Ideally I'd like something that could do both - a "racing" oriented road bike with a good range of gears so I could conquer some 18/19% grades with no problem.
That doesn't sound like endurance riding or training, so get a race bike with suitable gearing.
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Old 07-01-20, 11:03 AM
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Originally Posted by Iride01 View Post
Endurance bikes that I remember being called such back in the 1970's were more for those that wanted to put panniers and racks on their bikes and carrying a load of equipment while on multi-day rides and camping along the way.
That's a touring bike. Endurance bikes have almost nothing in common with touring bikes.

Edit: endurance bikes used to be the domain of very specific custom frame builders; Jobst Brandt used to ride a Peter Johnson frame that was very close to a modern endurance geometry. Rear wheel somewhat tucked under the saddle like a race geometry, and the front wheel out like a TT bike for straight tracking and efficient riding. (A friend up the street now actually has that PJ bike after Jobst could no longer ride it and later passed.)

Last edited by sfrider; 07-01-20 at 11:14 AM.
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Old 07-01-20, 11:58 AM
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Originally Posted by sfrider View Post
That's a touring bike. Endurance bikes have almost nothing in common with touring bikes.

Edit: endurance bikes used to be the domain of very specific custom frame builders; Jobst Brandt used to ride a Peter Johnson frame that was very close to a modern endurance geometry. Rear wheel somewhat tucked under the saddle like a race geometry, and the front wheel out like a TT bike for straight tracking and efficient riding. (A friend up the street now actually has that PJ bike after Jobst could no longer ride it and later passed.)
Yes you are likely correct. Regardless, I still recommend that no bike be rejected solely based on the segment it's marketed toward.

It is okay to reject them on looks. TT bikes to me are just Ugly....... IMO. So I'd never try one of them. Same for bikes that only come in blah colors. <grin>.
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Old 07-19-20, 08:47 AM
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Update

I ended up pulling the trigger on this bike. It's a Specialized Tarmac Expert Disc. The shop had no problem swapping out the 11-30 for the 11-34. I went on my first long ride with the new bike yesterday and I have to say I love it. I'm still getting a little used to the Di2 shifting, which seems to operate slightly differently than mechanical when shifting to a larger cassette or smaller chainring. I'm sure it will be second nature soon enough.

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Old 07-19-20, 09:18 AM
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Originally Posted by roadCruiser76 View Post
I ended up pulling the trigger on this bike. It's a Specialized Tarmac Expert Disc. The shop had no problem swapping out the 11-30 for the 11-34. I went on my first long ride with the new bike yesterday and I have to say I love it. I'm still getting a little used to the Di2 shifting, which seems to operate slightly differently than mechanical when shifting to a larger cassette or smaller chainring. I'm sure it will be second nature soon enough.

Kudos. Enjoy!
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Old 07-19-20, 09:36 AM
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Originally Posted by roadCruiser76 View Post
I ended up pulling the trigger on this bike. It's a Specialized Tarmac Expert Disc. The shop had no problem swapping out the 11-30 for the 11-34. I went on my first long ride with the new bike yesterday and I have to say I love it. I'm still getting a little used to the Di2 shifting, which seems to operate slightly differently than mechanical when shifting to a larger cassette or smaller chainring. I'm sure it will be second nature soon enough.

Nice bike! If not already explained by someoneelse here or by your LBS, DI2 comes with 3 different modes (manual, semi-synchro and synchro shifting). You might want to play with the 3 modes to see which one you like. Personally, I use semi-auto because I like to control my FD.
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Old 07-19-20, 12:16 PM
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Modes

Originally Posted by eduskator View Post
Nice bike! If not already explained by someoneelse here or by your LBS, DI2 comes with 3 different modes (manual, semi-synchro and synchro shifting). You might want to play with the 3 modes to see which one you like. Personally, I use semi-auto because I like to control my FD.
Interesting - I'll have to look into those. I think I've just been using manual mode so far.
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Old 07-19-20, 09:19 PM
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I like the full syncro, but there are times when the front and back shifing together doesn't seem to happen quick enough as I did with my 105 5800. It's as if the rear is too slow shifting down or up 2 gears.

However maybe it is because with my 105, I knew exactly when that was going to happen since I had to move both levers. With the full syncro, I sometimes don't realize that I'm going to the gear that requires the front to change.

Last edited by Iride01; 07-19-20 at 09:23 PM.
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Old 07-19-20, 09:43 PM
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You can also configure what the shift buttons do, it’s in the E-Tube software. Di2 is set as default to mimic how mechanical works, not sure what you found different unless it’s set for one of the Syncro modes.
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Old 07-20-20, 08:54 AM
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Originally Posted by wgscott View Post
I have the first gen ultegra 11-speed Di2, with a mid-cage rear derailleur spec-ed for 32T max. I can run a 36T cassette with no problem (just cranked on the B-screw a bit). A 46/30T GRX crank works fine with my Ultegra Di2 front derailleur as well. Shimano is very conservative with its specs.
What cons are there if you run a 11-28 or 11-30 on a mid-cage Di2 RD? Is it easy (i.e. without constant limit screw adjusting/reindexing) to swap between a "race" cassette and "climbing" cassette (like 10-30 to 10-34) if you have a mid-cage?
In the medium term, I've been thinking of maybe swapping out my short cage RD for the Ultegra RX Di2 so I can do occasional light gravel on my road bike but keep it with an 11-30 most of the time.
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