Barrettscv 

I’ll be installing my FC-RX810 48/31 on my Canyon Endurace this week. The bike now has a Ultegra R8000 50/34 with an 11-32 cassette. I rarely pedal at speeds higher than 35mph and I like the idea of staying on the big ring except on longer climbs of 5% or more. There are numerous 10-15% climbs in my area, so the 31/32 low gear will allow me to stay seated and spin my way to the top.

Cyclist0108

I think you will be quite happy with this. I bought the cheaper one, and it works flawlessly with my Ultegra stuff.

dwmckee

Do you have the GRX working with an Ultegra derailleur?

Barrettscv 

I’m going to install the matching RX-810 derailleur immediately. The R8000 front derailleur is shaped 53-50 chainrings while the RX-810 is for 50-46 chainrings. The RX-810 chainrings are approximately 2mm further offset from the center than the R8000 chainrings, this is another consideration. The RX-810 front derailleur provides for this wider chain line.

Cyclist0108

Yes. (Di2 Ultegra front and back, 46/30T GRX crankset, the front derailleur is clamp-mounted, and I had to crank down on the H-limit screw to the full extent, but it works great).

Cyclist0108

If you haven't already bought the GRX derailleur, you might want to give the one you have a chance first. (In my case, with Di2, replacing the front derailleur would necessitate replacing the rear derailleur as well, which would have been very costly, so I did the experiment, knowing I could go back to my White Industries 46/30T crank if it didn't work as well, but fortunately that wasn't an issue.)

Barrettscv 

The mechanical GRX derailleur is relatively easy on the wallet. If I had Di2, I’d certainly give the Ultegra a try.

Koyote

My shop installed the GRX 48-31 on my bike, and it did not function well with the original Ultegra FD...Needed to put on the GRX FD with the matching offset to shift properly with the GRX crankset. However, the Ultegra RD (8050) works fine with the setup.

Side note, but I have the best shop on the planet: this gear was on a four or five month old bike, and they swapped in the new bits and only charged me the extra cost over the original components; so, for instance, I think the new FD only cost me about $15.

Barrettscv 

Speaking of money, I’m very happy with the price and 10 day delivery time from https://www.tweekscycles.com/us/

Shimano GRX RX810 11-Speed Chainset - Double

SKU: MADFCRX8102E81
Crank Arm Length175mm 1 $180.83

Subtotal: $180.83
Delivery: $6.95
Grand Total: $187.78

srode1

Got mine for $179 free delivery from Western bike works when they had a sale last week. Competitive cyclist has a 20% off one item now, which would be the same price and delivered free.

Barrettscv 

1. 
   Looking correct, this is a functional and aesthetic improvement over the Ultegra
   
   Crankarm a clears the chain easily while on the big chainring and small cog
   
   Chain line on the small-small combination. No contact or interference
   
   Derailleur arm while on the small-small combination
   
   Derailleur arm on the big-big combination
   

srode1

1. 

Why run the front DR so high? I normally have mine much closer to the big ring / lower.

Barrettscv 

There is a correct amount of clearance. The cage moves downward while shifting, reducing the gap to about 1mm.

srode1

That's the gap I try to set up for, the picture looks bigger but must be the angle or its like you said the cage further out not over the big ring.

Barrettscv 

If you could actually see what your discussing, you would see you’re over-analyzing a bit. To paraphrase Groucho Marx: “(online discussions) is the art of looking for trouble, finding it everywhere, diagnosing it incorrectly and applying the wrong remedies”.

srode1

Huh? Not sure how this applies to my response, but ok if you say so.