Tycho Brahe 

My Ultegra RD-6800 is somewhat messed up, causing the chain to jump out of the pulleys. The pulleys were replaced not to long ago, but overall the derailleur has 10K miles.

My mechanic said the whole thing should be replaced instead of just the cage. Don't remember the reason, but I do trust him. He said Shimano is releasing a new derailleur, and I am better off waiting. The bike is rideable, just with the occasional issue.

Looked up this new RX-805, and the main benefit is the chain stabilization feature. I will occasionally bike on some gravel roads, but I never for long or fast. It appears that the main feature needs to be enabled with a button on the pulley. I can easily see myself not disabling it after a rough section.

Kind of want a new derailleur now. Mechanic said (last week), that the RX-805 is to be released in 2-3 weeks, but some online sites are saying that they are available on June 30.

Here is some marketing mumbo-jumbo from Shimano:

mstateglfr 

It's a clutch. Do you get a bunch of chainslap on your gravel sections? If so, then it could be beneficial.

the look of it is...distinctly mtb to me.

WhyFi

Yup, clutch. If you forget to switch it back, it's going to add a little more friction to the drivetrain. If you don't want to wait, I think that the r8000 is a Shadow derailleur (as opposed to the upcoming Shadow Plus with clutch), so it should reduce chain slap but not to the extent of the new one with the clutch engaged.

Tycho Brahe 

The question is does a normal roadie like me even need a clutch? Yes, I would ride a tiny bit of dirt every now and then, but I never go fast when I do. The dirt roads usually are short cuts to connect two paved roads. I do a lot of climbing, so sometimes I will experience chain slap with going down fast and hitting a pothole, but I tend to be in my biggest gears.

There is some extra weight, but not much (38g I believe). Some added cost.

redlude97

Unless you go 1X I think a clutch on even a gravel bike is overkill. Buy a lightly used 6800RD for $30 or a new R8000 for $50.

WalksOn2Wheels

https://bike.shimano.com/en-EU/produ...-RX805-GS.html

Wow. Ultegra RX. I didn't know they were doing groupsets in prescription strength now. I guess I need to make an appointment with my doctor. See if insurance will cover it.

MattyMurdah

+1 for just buying the new r8000 r derailer. I just replaced my damaged 6800 one with the new model and I'm happy I did because it protrudes a whole lot less (so when my wife/friend/cat/whoever tips my bike over and it falls on the drive side, I don't have to worry nearly as much about a bent derailer hanger.)

Kimmo

I think Shadow is an improvement... now we just need direct mount hangers to become a thing.

redlude97

improvement in function, not necessarily in looks. +1 on direct mounts though

cpach

It doesn't sound like you have a compelling need for the clutch derailleur. Get the RD-R8000-GS--it tucks the cage in for better protection and aerodynamics and is rated for up to a 34t cog.

Kimmo

Are you referring to what's inherent in the Shadow design, or just the styling?

I think it's a shame Shimano haven't emphasised the sleekness of it.

redlude97

I have one and function>form, but it just looks out of place on a road bike with its clear MTB roots.