Ultegra RX and GRX compatibility

[Bentley]

Curious, can you put a GRX Long cage on a Ultegra RX RD?

I can get the parts on the ‘bay, just don’t know if it’ll work.

TIA

[Hilltopperny]

Are they different? FWIW an Ultegra RX mid cage can shift up to a 40 tooth cassette without any issues.


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[Bentley]

Originally Posted by Hilltopperny

Are they different? FWIW an Ultegra RX mid cage can shift up to a 40 tooth cassette without any issues.


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I have a 36, says it’s good for a 34.

[jtbadge]

The RD-RX800 can easily handle an 11-36t in 2x. I have been running this combo for over a year with no hiccups.

RD-6800-GS before that with the same cassette, also no issues. Their advertised limits correspond to the cassettes they sell for a given line, not necessarily the derailleur's actual capacity,

You can also just use the GRX derailleur with your Ultegra shifters. But you won't need to.

[robt57]

The Shadow R8000-GS capacity is 39T. On my gravel bike it is running that with 11-42 and an 28/42 chainset. It is pushed out about as far past what you should for sure. And depending on RD hanger, you may or may not need a Wolfy Toofy...

[Bentley]

I have a 105 RD with a Wolf adapter... shifts like crap. I get it to shift but it’s slow and not crisp.

I have a mid cage Ultegra clutch RD, but I thought I would need a long cage, that’s why I asked.

That said, will a GRX cage work with an Ultegra RD? I know some one asked if they are different, I really don’t know, but they are clearly “labeled different.

Thanks

Ray

[Hilltopperny]

Originally Posted by Bentley

I have a 105 RD with a Wolf adapter... shifts like crap. I get it to shift but it’s slow and not crisp.

I have a mid cage Ultegra clutch RD, but I thought I would need a long cage, that’s why I asked.

That said, will a GRX cage work with an Ultegra RD? I know some one asked if they are different, I really don’t know, but they are clearly “labeled different.

Thanks

Ray

I have run the the Ultegra RX mid cage with a 52/36 mated to an 11-40 xtr with no wolf tooth. A 36 tooth should shift crisp without issue as long as it is tuned properly without the assistance of a goat link. The RX is nearly identical to the xt derailleur on my daughters mountain bike and that also runs a 40t large cog in the rear. I have not used the GRX stuff yet, so not sure if they are the compatible or not.


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[robt57]

Originally Posted by Bentley

I have a 105 RD with a Wolf adapter... shifts like crap. I get it to shift but it’s slow and not crisp.

What cassettes have you tried, I notice even a 32t cassesst shifts bad with mine. 36-40t cassette even with a short cage does well.

[Bentley]

Originally Posted by Hilltopperny

I have run the the Ultegra RX mid cage with a 52/36 mated to an 11-40 xtr with no wolf tooth. A 36 tooth should shift crisp without issue as long as it is tuned properly without the assistance of a goat link. The RX is nearly identical to the xt derailleur on my daughters mountain bike and that also runs a 40t large cog in the rear. I have not used the GRX stuff yet, so not sure if they are the compatible or not.


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Originally Posted by robt57

What cassettes have you tried, I notice even a 32t cassesst shifts bad with mine. 36-40t cassette even with a short cage does well.

Not sure how a 32 does poorly but a 36-40 does better... counter intuitive. I have a sunrace 11-36

[Hilltopperny]

Originally Posted by Bentley

Not sure how a 32 does poorly but a 36-40 does better... counter intuitive. I have a sunrace 11-36

I didn't have a problem with a 32 or 34 on the same bike. They were both Ultegra cassettes and shifted nice and crisp for me. My bike came with the 11-32 and then I swapped for the 11-34. I eventually wanted even more range and saw some threads and videos about the ability to run up to a 40t, so I gave it a shot. It worked for the longer slogs and steeper grades that I was riding. I eventually swapped the 52/36 2x for a 44t 1x and haven't gone back.

[robt57]

It was the 11-30t that shifter poorly, I correct my mis-statement.
The wolf tooth put the upper DR too far from the cogs. I thought I'd try it figuring if it was aligned it would work. It was poor at best.

[old fat man]

Why not try the mid cage that you have? Also, perhaps it's the SunRace cassette. Shimano 105 cassettes are very reasonably priced, might improve the shifting.

[SlowPokePete]

Originally Posted by Hilltopperny

I didn't have a problem with a 32 or 34 on the same bike. They were both Ultegra cassettes and shifted nice and crisp for me. My bike came with the 11-32 and then I swapped for the 11-34. I eventually wanted even more range and saw some threads and videos about the ability to run up to a 40t, so I gave it a shot. It worked for the longer slogs and steeper grades that I was riding. I eventually swapped the 52/36 2x for a 44t 1x and haven't gone back.

What cassette are you using?

I might want to try a 36, especially with the annoying skip I'm (still) dealing with using the HG-800 11-34 cassette...

SPP

[Bentley]

Originally Posted by old fat man

Why not try the mid cage that you have? Also, perhaps it's the SunRace cassette. Shimano 105 cassettes are very reasonably priced, might improve the shifting.

I was going to put it on, but after “discovering” it was likely not going to work I decided to see what the collective opinion is on “modifying” my RD with a GRX cage. Given the consensus that it will work fine I’m gonna try that first.

I will add, the Wolf Tooth works, but it’s a real compromise. I’m not sure if my performance is typical... but it’s not crisp at all.

[Hilltopperny]

Originally Posted by SlowPokePete

What cassette are you using?

I might want to try a 36, especially with the annoying skip I'm (still) dealing with using the HG-800 11-34 cassette...

SPP

I am using a XTR 11-40 right now without any issues. I am not sure if Shimano makes an 11-36, but I do know Sram does and 11spd cassettes are all cross compatible. I have Sram cassettes on two out three wheelsets that work with my current Ultegra drivetrain.


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