Using Shimano GRX Crankset with Ultegra Front Derailleur

[donalrey]

This is just an FYI, in case anyone was wondering on the compatibility of the new Shimano GRX crankset with non GRX FD - specifically Ultegra FD in this case. I couldn't find anything online regarding this so maybe this can help someone out.

Background story: I bought my gf the new GRX Crankset 2x11, 46/30t to replace an Ultegra 6800 50/34t for an upcoming trip. I bought it not realizing that Shimano recommends using specifically GRX FD because of the +2.5mm chainline of the new GRX 2x crankset. I decided to give it a go and installed it matching it with an Ultegra 6870 Di2 FD and it works just fine! I had to lower the FD and max out the high limit screw but shifting is pretty perfect. Alternatively, you can probably use one of these SRAM Wide Spacing Braze-on if you're worried about maxing out the high limit screw.

[marciero]

I just bought these to replace a 6700 compact with 46 large that got called to duty on another bike. I had thought these new GRX were 10 speed box has the "2x11" box checked rather than the "2x10". We will see how it works with 10 sp. Or I can just use an 11sp chain. As far as fd goes, I am not beyond bending 9 and 10 speed cages to get them to work, limit screw is a different story though. We will see.

[fa63]

Great to know; I am about to buy a 48/31 crankset for my gravel bike and was curious myself if I could tweak the non-GRX FD enough to make it work. Sounds like it is possible.

[Zee]

Useful news!

Did you happen to weigh the piece before install?

[PacNW2Ford]

Another data point: I am running 11-speed 8000 STI with a Rotor Aldhu 46-30 crankset with the wide "disc" (+2.5mm) chain line and a CX70 10-speed FD. It all works great. I have a GRX FD ready to swap in, but it's hard to take apart a perfectly functional setup. Especially since the CX70 looks much sleeker.

[marciero]

So mine is working great too with a 6700 (10 sp) deraileur. Limit screw adjusted out. The chain line is not too crazy either- The 46/36 cross-chain position is not too bad. I also do not seem to notice the increased Q from 148 to 151. This is odd since I noticed significant difference in the increase 145 to 148 on another bike going from Sugino to 6700.

[weiwentg]

Adding a couple data points from this thread on Gravel Cyclist. wgscott reported using a GRX crankset with 6800 Di2 derailleurs, but had to nearly max out the high limit screw. Nebo used a GRX with 105 (presumably mechanical) equipment, and reported that the trim is now useless but it works otherwise. hbs reported using GRX with Ultegra equipment, works great, no details.

[Morgul Bismark]

My current set-up on my B-Road:

• GRX FC-RX810-2 (48/31T) crankset
• Ultegra R8050 Di2 Front Derailleur

The R8050 FD is adjusted near the limit of the low adjustment screw. In addition to making the low range adjustment, I also moved the derailleur down a touch due to the minor difference on the high side between a 50/34 and 48/31.

Everything works just fine

[unterhausen]

this discussion is making me wonder how I got a CX-70 to shift a mtb crank with a 2.5mm spacer on the drive side.

[45K10]

I just put a 46/30 GRX crankset on my wife's bike. I got it to work with a Athena FD without any issues. She is also running a Athena 11 speed RD with a Centuar 12-32 also without any issues.

[LewisQC]

Probably a dumb question and little bit out of topic but I have Ultegra (R6800) crankset 50/34 on my Devinci Hatchet carbon 2017 and want to go 46/30 at the front.
I was looking at FSA energy but would need a new BB. My bike is PF BB86. Should I be able to swap my Ultegra cranks to one of GRX option without any other modification? I only see compatibility for SM-BB72.

Thanks in advance

[leftsidedrive]

Originally Posted by LewisQC

Probably a dumb question and little bit out of topic but I have Ultegra (R6800) crankset 50/34 on my Devinci Hatchet carbon 2017 and want to go 46/30 at the front.
I was looking at FSA energy but would need a new BB. My bike is PF BB86. Should I be able to swap my Ultegra cranks to one of GRX option without any other modification? I only see compatibility for SM-BB72.

Thanks in advance

Not a dumb question. The BB standard (hollowtech 2) is the same for the GRX and the 6800 crank. You do not need to change BB's.

The grx specific FD is to address the change of the chainline standard the group is built around. The GRX group has a slightly wider chainline to work with modern "gravel" bikes that need wider tire clearance. Yes, a standard 11 spd fd will work, but you will find that it struggles to get outboard far enough. I've set up a few of them now that don't even hit the high limit screw. The new crank flat out works better with the GRX specific FD.

Also, I've found the GRX crank prefers a clamp style fd mount opposed to the braze on style. The braze on style can sometimes limit the amount you can drop the FD to accommodate the 46 or 48 big ring.....

Blah blah blah....

I really recommend people check out a gear inch chart to help them decide if a GRX front end is a good choice for them. You can see far lower gearing drops by running a 11/34 cassette if you haven't done that already. Gear inch per dollar is where its at right now in modern road drivetrains. If you are spending 300 dollars to drop 1.5 gear inches, you might be wasting your money...

It's funny about our industry. We are constantly reinventing the wheel for no other reason than marketing purposes. A "boost" chainline has existed for years with a 73 or 83 mm BB. Some ding dong at a major company just renamed it so they could be on the cutting edge of cycling technology.

I install these things all day at work. Everyone's idea of "it works just fine" is different. Feel free to PM me if you all have any questions. I'll be glad to chime in my 2 cents or help anyone with questions about compatibility.

[LewisQC]

Originally Posted by leftsidedrive

Not a dumb question. The BB standard (hollowtech 2) is the same for the GRX and the 6800 crank. You do not need to change BB's.

The grx specific FD is to address the change of the chainline standard the group is built around. The GRX group has a slightly wider chainline to work with modern "gravel" bikes that need wider tire clearance. Yes, a standard 11 spd fd will work, but you will find that it struggles to get outboard far enough. I've set up a few of them now that don't even hit the high limit screw. The new crank flat out works better with the GRX specific FD.

Also, I've found the GRX crank prefers a clamp style fd mount opposed to the braze on style. The braze on style can sometimes limit the amount you can drop the FD to accommodate the 46 or 48 big ring.....

Blah blah blah....

I really recommend people check out a gear inch chart to help them decide if a GRX front end is a good choice for them. You can see far lower gearing drops by running a 11/34 cassette if you haven't done that already. Gear inch per dollar is where its at right now in modern road drivetrains. If you are spending 300 dollars to drop 1.5 gear inches, you might be wasting your money...

It's funny about our industry. We are constantly reinventing the wheel for no other reason than marketing purposes. A "boost" chainline has existed for years with a 73 or 83 mm BB. Some ding dong at a major company just renamed it so they could be on the cutting edge of cycling technology.

I install these things all day at work. Everyone's idea of "it works just fine" is different. Feel free to PM me if you all have any questions. I'll be glad to chime in my 2 cents or help anyone with questions about compatibility.

Great info. Thanks a lot... I've been thinking about smaller gearing for a while on my bike. I already have a 11-32 cassette at back (and a 12-25 for indoor riding during winter). I'm more into mountain biking than road or gravel but when I do ride my Hatchet I'm mostly alone on week days. I don't mind having a lower top-end so to me, a 46/30 or 48/31 makes sense . Smaller gap/range cassette for road ride without too much climbing, and 11-32 for longer rides, light-bikepacking or gravel. I intend to do Paris to Ancaster "race" in Ontario this spring and could use lower than 34-32 for the final climb... I could walk that last part like many do, but I guess I'm just looking for a raison to make the move to sub-compact...

My bike has a braze-on type FD but I still got probably 8mm of downward movement possible which should be ok for at least a 48... I don't need the +2.5mm chainline though. Maybe I should go with FSA Energy cranks (can get them pretty cheap from germain web site) and a new BB. But I would need to bring my bike to LBS for that...

Maybe I would be ok with a 11-34 cassette with my actual 50-34 crankset...

[timtak]

I am having a similar problem with a modern 105 (FC 5700 or 5800) (hollow looking) crank and chain-rings, on a Ultegra 6600 gruppo bike. The old Ultegra front derailleur does not reach out far enough to get on the new big chain-ring with the outer adjustment screw turned as out as possible.

Would someone be so kind as to tell me whether the solution to is to purchase a newer 105 front derailleur, or whether there is some other possible work-around to get my chain out further using the Ultegra brifters and Ultegra front derailleur.

If the 105 crank is a 5800 then it will be 11 speed as opposed to 10 speed but I don't think that should be much of an issue on the front.

[sg8357]

Originally Posted by unterhausen

this discussion is making me wonder how I got a CX-70 to shift a mtb crank with a 2.5mm spacer on the drive side.

The CX-70 has a larger than normal range,
I've used them on a 126mm oln bike with a 46/30 and a 135mm oln bike,
works great.

I just finished the GRX 48/31 with GRX front mech, Ultegra 8000 shifters,
trim is right on, shifting is spooky smooth. Rear spacing 135mm, 8cm bb drop.
So FD need to be raised, and Shimano's inner limit adjustment method,
left the cage too close to the inner ring.