GRX first report

[Clean39T]

Originally Posted by weaponsgrade

Is this the 810 GRX RD? How does it handle the big-big combo (48 front ring / 42 rear cog)? I have an RX800 RD. Both RDs are rated for a max 34T cog. I'm running an 11-40 and I'm not noticing any negative shifting. I've even got some room on the b-screw, so maybe it'll handle a 42t. However, I think the big/big would be a problem. I can go big/big (48/40) with my RX800, but that's really pushing it. I think the RD would get ripped off if I went with a 42 cog and accidentally shifted into the big/big.

Why would one need/want to run that combo? Di2 shifts so easily, why not use it and drop one up front and one in the back when needed?

Sent from my Pixel 2 XL using Tapatalk

[weaponsgrade]

Originally Posted by Clean39T

Why would one need/want to run that combo? Di2 shifts so easily, why not use it and drop one up front and one in the back when needed?

Sent from my Pixel 2 XL using Tapatalk

I don't have Di2, but have steep hills.

[Clean39T]

Originally Posted by weaponsgrade

I don't have Di2, but have steep hills.

I meant big/big, vs. dripping down to the little guy up front.....

Sent from my Pixel 2 XL using Tapatalk

[weaponsgrade]

Originally Posted by Clean39T

I meant big/big, vs. dripping down to the little guy up front.....

Sent from my Pixel 2 XL using Tapatalk

I'm pretty good at avoiding big/big, but I find comfort in knowing that if I accidentally shift into it that my RD won't rip out. My own personal experience is that the RX800 will handle a 48/40 but I can't see it handling a 48/42. The comment about a shop promoting a GRX RD with an 11/42 cassette and a double crank with a 48 is interesting because the GRX 810 and RX800 have the same max cog rating and the other specs are similar.

[Hilltopperny]

Originally Posted by weaponsgrade

I'm pretty good at avoiding big/big, but I find comfort in knowing that if I accidentally shift into it that my RD won't rip out. My own personal experience is that the RX800 will handle a 48/40 but I can't see it handling a 48/42. The comment about a shop promoting a GRX RD with an 11/42 cassette and a double crank with a 48 is interesting because the GRX 810 and RX800 have the same max cog rating and the other specs are similar.

I am pretty sure I had 52/40 work although I did not ever consciously use it. I did seize it up with 52/42, but caught it just in time. That prompted a move to 44t 1x with a 10-42 which works great.


Sent from my iPhone using Tapatalk

[Kirk007]

Get the 812 rear derailleur with long cage - works fine with 10-42

Sent from my moto z3 using Tapatalk

[HTupolev]

Originally Posted by Kirk007

Get the 812 rear derailleur with long cage - works fine with 10-42

The cage on the RX812 is not longer than the cage on RX810. Its geometry is designed to clear big cogs just fine, but it's not designed with loads of chain wrap in mind, since it's not intended to deal with a front difference in addition to a big cassette. And because there's a large offset between the cage pivot and the jockey wheel, using it in a multi-ring drivetrain might degrade rear shift performance.

[Kirk007]

Originally Posted by HTupolev

The cage on the RX812 is not longer than the cage on RX810. Its geometry is designed to clear big cogs just fine, but it's not designed with loads of chain wrap in mind, since it's not intended to deal with a front difference in addition to a big cassette. And because there's a large offset between the cage pivot and the jockey wheel, using it in a multi-ring drivetrain might degrade rear shift performance.

thanks for the further insight; glad I'm running 1x then.