Planning to building a custom gear ratio that will have a new 11-42 2x11 speed cassette (XT?) . I think 42/26 or 44/28 are quite possible, but then I thought that maybe I can stretch it into 44/26t.
This would require FD capacity of 18, RD - 49. I hear that most rear derailleurs are quite conservative in their chain capacity specs and can be pushed by 2-4 teeth, not sure if this applies to fronts as well. I see Shimano is offering 47T RDs and 16-17t on the front.
So is this feasible or shall I lower my expectations and go with 42/26 or 44/28? Has anyone tried this? Is it worth the hassle? Though I might still try it purely for fun if it is possible.
Some folks used to use triple cranksets with ranges greater that 20T so suitable front derailleurs should exist. Personally I wouldn't go that wide with a double because it won't shift as well as a closer ratio and you'll either get a huge jump or need multiple rear shifts every time you shift the front. I think rear derailleurs shift better than fronts over a wide range, that's probably one reason 1X setups are getting popular.
I'd worry less about the chain takeup on the rear derailleur because I never use the smaller half of my cassette with the small chainring. I also don't use the 2 or 3 largest cogs with the big chainring but I make sure the big/big combination works in case I get to it by accident.
FWIW we have a similar setup on our tandem but it's SRAM 10x42 11spd cassette and a road crankset with 52/46 chainrings. We have a Wolf Creek's RoadLink on the RD to handle the large cogs. The basic limitation with this setup is the derailleur cannot handle that much chain wrap I so set the chain length to accommodate cross chaining on the big-big and then I only use the 7 or 8 largest cassette cogs when I'm in the small chainring. If I'm in the small chainring and accidentally shift into too small of a cog it makes some noise but doesn't seem like anything to worry about. But that's just my experience on the tandem and with road bikes over the years where I'd force a drivetrain on a RD which didn't have sufficient capacity.
One more concern - if you exceed the capacity of the FD the most typical problems will be: 1. Chain will rub on the rear of the derailleur when using the small cogs as it won't drop down far enough. 2. Poor shifting as the FD cage will be higher than ideal for the small chainring position. If the FD is lowered to an ideal position for the small chainring then it will not clear the large chainring. The Shimano GRX FD is rated to handle 17t difference (48/31), so maybe this won't be an issue for 18t???
I can't say if it will work or not, but I have definitely wanted to try it before. I"m running 40x24 with a 11--42 on my dual-suspension drop bar bike and I want to try it so I can ditch the 11. I hate the eleven to thirteen jump most every time. Since shimano is so conservative, I wondered if the GRX would get it done. It would definitely require shifting retraining because that 18-tooth will require double shifts nearly every time. Di2 would make it easier by not allowing the big/big and small/small, but then you would need to run the front derailleur with the 817 which technically is only 1x, though I have read one guy who said it would work but not in full Syncro.
NoCoGreg wrote:The Shimano GRX FD is rated to handle 17t difference (48/31), so maybe this won't be an issue for 18t???
Was thinking about the GRX, but I think I will have to pass. My current chainline is 44mm while GRX has 47mm, I prefer to stay as close as I possible to what my frame was designed for. I guess I will have to mix an Ultegra FD (16T capacity) with an XT RD (47t capacity) and
Make it work with 42/26 first
Then replace 42t with 44 and see if it still works. Or maybe even try 42/24 just for fun, because cogs are cheap so why not? 😁
Maybe someone has better ideas, would be glad to hear.
Was thinking about the GRX, but I think I will have to pass. My current chainline is 44mm while GRX has 47mm, I prefer to stay as close as I possible to what my frame was designed for. I guess I will have to mix an Ultegra FD (16T capacity) with an XT RD (47t capacity) and
Maybe someone has better ideas, would be glad to hear.
Per Lennard Zinn at Velo News, yes your concerns re. chainline are well founded: "... GRX double cranks and GRX front derailleur must be paired together."
NoCoGreg wrote: Per Lennard Zinn at Velo News, yes your concerns re. chainline are well founded: "... GRX double cranks and GRX front derailleur must be paired together."
Was thinking about the GRX, but I think I will have to pass. My current chainline is 44mm while GRX has 47mm, I prefer to stay as close as I possible to what my frame was designed for. I guess I will have to mix an Ultegra FD (16T capacity) with an XT RD (47t capacity) and
Make it work with 42/26 first
Then replace 42t with 44 and see if it still works. Or maybe even try 42/24 just for fun, because cogs are cheap so why not? 😁
Maybe someone has better ideas, would be glad to hear.
I began on a 26t then went 24, 23, and ended up on 22t. 40/22 but 10sp Sram using an XX.
What front derailleur do you use with your 40-24? Most of the Gravel/Road double FDs are specified to have min 46t on the ou ring.
It is a direct mount XT on a 2015 Turner Czar. It is still Mechanical because the Di2 would not clear my rear suspension. Rear is Di2. The FD is supposed to be 14 max, but it seems to work fine at sixteen. I have a secondary rigid all-road bike made for climbing that I fiddled with a mech Ultegra FD on a carbon mtb frame. It seems to shift the 40-24 just fine as well. I've been wrenching bikes going on forty years and that helps when you are trying to do some nonstandard things. You have to be prepared for some frustration, though; sometimes you just can't make something work.
I'm running an Ultegra 8050 di2 FD with the GRX 817 di2 RD. Indeed no synchro shifting (but who cares?) but otherwise ideal: smallest QF + bigger cassette range. This way I can use any road crank (in my case a road Rotor 2inpower crank with 46/30T) and space it out symmetrically (the fixed axle of the Rotor is too short to add 2.5mm each side).
The +2.5mm GRX chain line & GRX cranks are only really needed when having a 73mm instead of 68mm BB. The 5mm wider BB makes it easier for bike frame manufacturers to clear wider tires, this is how they have been clearing wider tires on MTB for years. There are not a lot of gravel bikes outside of the Focus Atlas and some Salsa bikes with a 73mm BB, as a result these all have boost wheels (148mm in the back) as well bringing the cassette 3mm outwards to fix the chain line... like on MTB.
You could even say that the GRX chain line is too far out with 142mm wheels, creating more cross chaining on the bigger rear cogs then necessary?
I used a 42/26 with a 10/42 SRAM 11 speed cassette on a handrail MTB. I used 2x11 SRAM GX shifters and rear derailleur. RD capacity was good and they say 42t max cassette. B screw was just long enough for the 42. All in all it worked very well. It does require double shifts occasionally and I found myself cross-cbained often. I eventually went back to 1x11 for the simplicity of it. For me the easy gears were too easy and I hardly used the big ring.
This topic has been discussed several times with some have more success than others. After trying combinations of rear derailleurs, I was able to get an 11-42 to work with a 46-30 only by using an XT rear derailleur with a Wolf-Tooth TanPan adapter. Shifting is fine and I can use the entire range with both front chain rings, not that I ever will.
Others had success without an indexing adapter, but never had the full range of gears. The only reason why I don't like this option is that "operator error" can cause the rear derailleur cage to hit wheel spokes.
Just found this video, 46/27T on the front seems to be working well. I think he has Ultegra FD, that is specked for 16t capacity however it handles the whole 19t in this setup. I'm actually planning to use rebranded Sugino cranks, so I'm optimistic 🙂.
We've done it on the regular, typically with an XT front (47mm I think) but also with Sensah and Ultegra (with a 44mm chainline) The "shift up" is a bit slower than you might expect but the shift to the smaller ring is fine. We do shorten the chain a bit below what might be "normal" so that the BIG/BIG combo isn't really possible and there's a deliberate 'rub' in the small chainring so that the smallest two cogs on the cassette aren't really useable because of chain slap anyway. So if you setup the chain the way you usually do and then remove a link (sometimes two) then the length should be perfect. We have gone up to an 11-46 in the back with Di2 (programmed to multishift so as to avoid these extreme gears discussed above). Our normal gravel drivetrain is an 11-40 and 46/30 so this is a small stretch from that standard drivetrain. We get Albino cranks and chainrings from Merry to put them together but any 110/74 works fine.
2. Poor shifting as the FD cage will be higher than ideal for the small chainring position. If the FD is lowered to an ideal position for the small chainring then it will not clear the large
Yes, this is exactly what I see after swapping 50/34 with 42/26. I haven't changed my rear cassette yet, only cranks/chainrings and I can't get my FD shifting between the small and large.
Hope I can fix it with BB spacers, if not I will have to upgrade my FD.
Finally managed to get my existing 10 year old microShift FD with an SRAM Impulse shifters to work with my new 42/26t crunk.
Took me a couple of days to tune the derailleur and find the correct BB spacer for the new crunks. A bit of rubbing while cross-chaining, but it works.
Next step is to change the rear cassette to 11-42 or similar.
For what its worth I have a ‘21 Topstone 1 where i switched the cranks to GRX 48/31 & 11 speed 11-42 cassette with GRX 800 FD, GRX 810 Shadow + RD and GRX 600 shifters and it works great. Will try the 11-46 shimano cassette but believe this will require a WolfTooth RoadLink DM. Ideally I would love to convert to Di2 or even AXS.
