Lazyass

Does anyone have one of these yet? They have a mechanical and Di2 version. I'm planning for a CX build strictly for racing, and just learned about these. Wondering how well they stop chain slap and would also like to find out if it's compatible with RS505 hydro shifters. If not that would probably be a deal breaker for me.



https://www.bikeradar.com/us/road/ne...and-di2-52018/

gus6464

All Shimano road has the same pull ratio so it will work with your shifters.

Facanh

They're compatible with 11spd road stuff.

If it was up to me I would make clutch RDs mandatory on every single bike that has a rear derailleur. They're just awesome.

First I had a Shimano clutch RD on a 10spd straight bar hybrid, and now SRAM 1x11 on my gravel bike. Once you experience the quietness you can't go back. IMO.

FlashBazbo

Yes, you can. I did. They are quiet, but they also create quite a bit of drag in the drive train. I'm not sure how many watts you lose, but it's enough to feel. Over the course of a Dirty Kanza 200, I think the added drag is worse than the possibility of a dropped chain. (And chain catchers don't cause drag.)

Of course, you can turn off the clutch on a Shimano rd (not a SRAM). But with the clutch off, you don't get the benefits of the clutch in the rough stuff.

Facanh

That's why I wrote IMO at the end.

Not trolling, I don't understand how clutch RDs can cause drag in the drivetrain. Could you explain? The clutch only makes the cage harder to rotate forward, how does that translate to lost watts?

Sure, shifting up the cassette requires a tiny bit more force since you're fighting the clutch, but I still don't get the drag thing.

gus6464

Shimano let's you set the tension on their clutch while I think SRAM does not.

FlashBazbo

The added shift force is a second symptom (drag being the first) of the same issue. The clutch maintains tension on the chain by exerting force on it -- pressing the jockey wheels against the chain with enough force to keep it solidly against the rings even in the face of severe shocks. If you're riding a mountain bike, the chances of frequently dropping 3 feet or so and dropping a chain are a lot higher, so the increased drivetrain drag is considered a necessary evil. On a gravel bike, if you never ride over anything rougher than a railroad crossing, the derailleur clutch provides zero benefit in exchange for the added drag.

Facanh

Still not trolling. But I still don't see it. The clutch can't put more tension on the chain, the spring does that. The clutch lives on the pivot point of the cage, and it simply adds more friction to that pivot point. You get less chain slap because the cage can't rotate forward as much, so it keeps that tension in the chain better. If you would weld the cage so it wouldn't be able to rotate you would get the same result, but you couldn't shift.

The Shimano one is super easy to take apart, do it and you will see, or just watch this video:


It's basically just a spring pushing against a steel drum and that's it (and there is a one way needle bearing so it only works in one direction).

FlashBazbo

I'm not here to argue theory with you. I've experienced the drive train drag myself. I rode a clutched rear derailleur on my gravel bike for a couple years. The drag eventually bothered me more than the possibility of a dropped chain.

Lots of people have shared the same experience that I've had. We've felt it for ourselves. But maybe we're all delusional and you're not. It's possible.

Facanh

I'm not trying to argue either, and I don't want to be rude, but I think you don't understand how it works. You're saying that a friction device on the pivot point of the cage puts more tension on the chain. That doesn't make any sense to me, and i'm just trying to understand it.

Sure, you could experience something, but if you can't actually explain why...

Personally I don't experience the drag. On my Shimano 10spd when I turn off the clutch, shifting gets a bit easier up the cassette, but that's it.

On my Rival 1 RD I can't turn off the clutch, but it runs much smoother and quieter than my 10spd Shimano group even with the clutch turned off... So both groups have a clutch, yet one feels less draggy.

Marcus_Ti

Someone over on RBR got one last week. Wish Shimano had warned us they were coming...or better still released them with the regular Ultegra 8000 kit rather than waiting until June/July.

gus6464

I have never seen any video or lengthy discussion about clutch RDs causing any significant drag. What they for sure do is make it a little harder to shift because of the increased cable tension. I can see it causing drag if you put way too much tension on the clutch but that's about it.

HTupolev

To my understanding, in addition to the clutch, clutched rear derailleurs typically have stronger springs than unclutched derailleurs, which could increase tension (and therefore drag) on the lower run of the chain.
It's also possible - although I'm sure that this is a complicated issue - that the increase in tension from the clutch refusing to let the chain bounce increases drag on the lower run of the chain.

What magnitude these effects might have, I have no idea.

gus6464

I'd be curious if anyone has actually measured the increased drag vs "ohh I can feel it for sure".

FlashBazbo

I don't know, but here's what Bike Radar and others who have reason to know say about it in Bike Radar's PR piece on the introduction:

"Mountain bikers generally leave the clutch in 'on' position and only turn it off to ease the installation and removal of the wheel from the frame. It’s very likely that we’ll see more use of the on/off switch on road bikes as the clutch does add a small but measurable amount of friction."

"Going on feedback from riders in the past, they don’t have problems with their drivetrain per se, but sometimes the tension will drop for a split second on really rough sections. There is maybe a small penalty in efficiency [with a clutch derailleur], but in a race like Flanders or Roubaix, you are losing a lot more when your drivetrain isn’t engaging smoothly because of chainslap." - Matt Shriver, Trek Segafredo Technical Director

"Friction Facts founder Jason Smith has said clutch derailleurs — referencing SRAM's Force 1 derailleur at the time — do add a bit of resistance to the drivetrain."

And per Road Cycling UK (another of the dozens of friendly, almost identically worded, Shimano press releases the week Shimano officially didn't announce the derailleur):

"The benefits to professional road cyclists are less obvious - with increased chain tension comes the marginal loss of precious watts - but for the cobbles of the Spring Classics, the extra chain security may may prove advantageous."

Google is your friend.

TimothyH

The RX-805 is not listed in the current Di2 compatibility chart.

The web pages for the RX-800 and RX805 both say, "Compatible with current road DUAL CONTROL LEVER."

The RX805 Di2 version is $226 from Alex's Cycles in Japan. The price may fluctuate due to the exchange rate.

https://alexscycle.com/products/shim...ear-derailleur

I have a few really rough descents that make me wish I had a clutch derailleur. I may have to consider this.


-Tim-

ph0rk

I have one in a box (RX800) - I preordered it a few weeks ago while drunk and it showed up. According to Shimano it is compatible with all modern cable-pull 11 speed stuff. I'm betting it will work with the newest Tiagra, too. Still waiting on wheels for the build.

As for whether or not a Clutch RD is worth it - that all depends on how gnarly your gravel is.

FWIW when I went clutchless to clutched with a SRAM setup I never noticed increased shifting force. Stiffer springs, on the other hand, sure. I did notice less chain slap and fewer dropped chains.

DrIsotope

I ride a bike with an RD-6800 one day, and one with a clutched Rival 1 the next. I notice absolutely no difference. If there's more drag, it is to me imperceptible.

I also descend service roads so rough the bottles start trying to jangle out of the cages, so I'm thankful for the clutch.

faulker479

With a full suspension MTB, i can see there being some extra tension/drag when not shifting, but since I've never been on a road/gravel bike or hard tail MTB with a clutch, I would have to ride it to figure it out. My only experience with a clutch drivetrain is the first gen Shimano XT 10spd. I would think that with a chain that isn't worn out, it shouldn't be too much.
I would need to ride one setup for a while, let the "this is awesome"/new toy is better feeling go a way, and then go back to the other to be able to really tell.
When I switched my road bike from 6800 level Di2 to 9100 level Di2, the shop owner asked me if I felt the difference. I told him not really. Same thing when I changed out my bottom bracket to a ceramic Kogel.

cobra_kai

Diamondback investigated the drag issue and found that the drag increase in a clutched 1x11 system over a 2x11 system is negligible and from a system POV the 1x system is often a net gain because of aerodynamic improvements from removing the front derailleur. This was for a triathlon application so the aerodynamic portion is sort of irrelevant but the lack of increased drag is the important part. Here's the link if you're interested in a long read: https://ride.diamondback.com/frictio...1x-drivetrains

Metieval

guys complaining about drag on clutched derailleurs, probably shouldn't be riding on bikes with tires bigger than 25c.....

redlude97

I wouldn't say lack of increased drag, they estimated the loss at 1w. While not a lot in relative to total power output, it does represent a significant increase in drivetrain friction losses which sum to ~7-10w

cobra_kai

While I agree 1 watt =/= 0 watt, for someone to say it's a significant affect on a race is ridiculous.

birru

I installed my RD-RX800 over the weekend on my 2017 Jamis Renegade Expert, upgrading from the RD-5800-GS. It feels really, really good. The clutch works well at stock settings. I haven't messed with adjustments yet. The clutch seems to add zero resistance to the drivetrain, or if it does it's imperceptible. I don't see how the clutch would add resistance to the drivetrain to be honest. Where I notice a difference is in shifting speed when shifting up, and a touch more effort at the lever when shifting down. It's not a huge deal. I'd just leave the clutch engaged all the time if it wasn't for the fact I'd be wearing away at the friction material needlessly. I'm not sure how long the material is supposed to last.

redlude97

Again no one has said that. It also hasn't and won't stop me from using clutched deraillers, but for example after ~3months of hard training I've only increased my FTP by 13 watts this season, 1 watt is almost 10% of my gain.