GRX Di2 vs Ultegra 12speed Di2

[PaMtbRider]

Has anybody ridden both and have a strong preference one way or another? This will be going on a 650B gravel bike.

This will be a double chainring setup with an aftermarket crank so gearing options don't come into play.

I prefer the looks of the Ultegra and the semi wireless aspect, plus it's 12 speed so it has to be better

GRX has the benefit of a clutch rear derailleur. This is the one big plus so far since this will occasionally see some chunky gravel.

I think they both have servo wave braking. Are there any other differences I should know about?

[EB]

Originally Posted by PaMtbRider

Has anybody ridden both and have a strong preference one way or another? This will be going on a 650B gravel bike.

This will be a double chainring setup with an aftermarket crank so gearing options don't come into play.

I prefer the looks of the Ultegra and the semi wireless aspect, plus it's 12 speed so it has to be better

GRX has the benefit of a clutch rear derailleur. This is the one big plus so far since this will occasionally see some chunky gravel.

I think they both have servo wave braking. Are there any other differences I should know about?

GRX has a slightly different chainline - 46.9mm vs 44.5mm on Ultegra 12. I believe you use slightly different spacers on the GRX crank assembly as a result. Given that you’re using an aftermarket crankset, I’m not sure this matters either.

It doesn’t look like they are making the fabled RX805 rear derailleur in 12 speed flavor - that would give you the clutch.

[Dave]

Grx chain line is built into the crank. No spacers used. Be sure an after market crank will work with the grx FD.

The grx 11-34 still has nasty 11-13-15... jumps between sprockets.

[Yoshi]

Personally I don’t think Ultegra 12 speed Di2 shifting is any better than the previous iteration but the disc braking sure is.

[Clean39T]

The GRX shifter are great for folks with larger hands and there are thumb buttons that allow etap-style shifts when you're tucked down (left goes up, right goes down - in the rear). The RD is not as smooth though as a RX805 or Ultegra Di2. My perfect setup for all-road would be a 32/48 up front, 11-36 SRAM in the rear, GRX Di2 shifters, Ultegra Di2 FD, and RX805 RD.

[Dave]

Almost like my grx 46/30 crank, 10-36 sram axs cassette, plus axs shifters. Great for small hands. Really wide range.

[rice rocket]

GRX is best for what you're wanting, I'd consider the clutch mandatory for any actual gravel riding.

I wish they put that lever shape on the Ultegra Di2, maybe in a few generations (or when SRAM decides to copy and forces their hand).

[John H.]

Having live through 11 speed 2x with 34/50 on gravel I suggest GRX. I can't count how many times my chain flew off on bumpy descents with a non-clutch rear derailleur.

[scoobydrew]

Originally Posted by Clean39T

The GRX shifter are great for folks with larger hands and there are thumb buttons that allow etap-style shifts when you're tucked down (left goes up, right goes down - in the rear). The RD is not as smooth though as a RX805 or Ultegra Di2. My perfect setup for all-road would be a 32/48 up front, 11-36 SRAM in the rear, GRX Di2 shifters, Ultegra Di2 FD, and RX805 RD.

I can attest the GRX Di2 shifters are also great for small-med hands. The brake lever actuation/pivot point is great when you're on the hoods over rough stuff.

I also agree with every component choice on the above recommendation. I'm running something similar (46/36, 11-36 SRAM, otherwise GRX FD and RD) and it's served my well both on/off road.

[dddd]

Unless I was going to be using a really wide rear tire, I would much prefer the Ultegra chainline/Q over that of the GRX, so would use the Ultegra FD as well.

[rice rocket]

Originally Posted by dddd

Unless I was going to be using a really wide rear tire, I would much prefer the Ultegra chainline/Q over that of the GRX, so would use the Ultegra FD as well.

Really depends on your frame. Low Q-factors don't work on frames with high tire clearance.

I had heel strikes with my road cranks + XTR pedals, I had to get the extended axle pedals to clear, which negated the possible benefits of the lower Q-factor. After the first few rides, I can't say I've noticed the difference but maybe I'm not sensitive to it.

[PaMtbRider]

Thanks for the feedback. FWIW this will be for my small handed wife, not big handed me. The plan is a No22 Drifter with 650B wheels.

[CNY rider]

Originally Posted by PaMtbRider

Thanks for the feedback. FWIW this will be for my small handed wife, not big handed me. The plan is a No22 Drifter with 650B wheels.

Oh my.
That is some lucky wife!

[GregL]

Originally Posted by CNY rider

Oh my.
That is some lucky wife!

I think the luck goes both ways. After watching her ride very fast on loose gravel, with comparatively skinny tires, I was highly impressed! Such great talent deserves an equally great bike!

Greg

[PaMtbRider]

Originally Posted by GregL

I think the luck goes both ways. After watching her ride very fast on loose gravel, with comparatively skinny tires, I was highly impressed! Such great talent deserves an equally great bike!

Greg

You guys are too kind. Luckily she only reads the posts here that I show her.

I think it also says a lot for a well designed steel frame and fork. Her Kirk definitely does not suck, and the Drifter will compliment and not replace it.