Sram eTap rear derailleur sporadically stops shifting - then performs all queued shifts at once?

Discuss light weight issues concerning road bikes & parts.
XCProMD
Posts: 880
Joined: Sat Jan 26, 2008 10:25 am
Location: Cantabria

by XCProMD

Jugi wrote:
Jugi wrote:
Thu Oct 24, 2019 7:57 pm
As I was able to observe a clear change in the RD's behaviour, I'm starting to get slightly hopeful about reviving this thing. I decided to put the RD back on the bike while it's on the trainer, and test ride it for some time to see how frequently the jams happen in zwifting.
As a follow up to this:

This particular rear derailleur has been ridden for 107 hours 27 minutes between Oct 24th - Feb 14th exclusively on Zwift. Riding time has consisted of mainly free riding (easy rides, workouts in free ride mode, segment hunting and races) and only a couple of ERG mode workouts, which of course do not necessitate many shifts at all. Tacx Neo (1gen) has been responsible of resisting me in my garage. The garage has stayed quite consistently between 0°C...+8°C during the winter. Shifts have been mainly single shifts, but every now and again I have used the shift burst (ie. descending from Watopia's Epic, as both sides of the mountain have short & sharp inclines when going down). Cassette and chain used have been the SRAM PG-1170 11-25 and SRAM Red 22.

During this time period, I made a remark of only one shift which might have completed with some additional hesitation. Other than that, perfect operation for 107 hours. I don't have an easy way to count the number of shifts, but there have been plenty.

I suspect the non-changing training conditions and the cool ambient air may have some effect in the RD's flawless performance. It will be interesting to get this unit on the road when the season starts.
So, Jugi, this pretty much proves that there’s nothing wrong with the mechatronics but the problem are the pivot bushings. Would you agree with this?


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by Weenie


Jugi
Posts: 678
Joined: Sun Jun 24, 2018 8:10 am

by Jugi

I can't tell for sure, but I have a suspicion there was something physically resisting the arm which actuates the parallelogram and is connected into gearing (or the servo itself?). During the final service I did, I spent plenty of time wiggling that arm and testing it back and forth without any resistance. I'm quite sure about the issue being mechanical and not electronic in nature.

It bugs me I didn't found any clear issues in any bushing or pivot, but this RD has still kept working perfectly after transitioning to outside riding.

XCProMD
Posts: 880
Joined: Sat Jan 26, 2008 10:25 am
Location: Cantabria

by XCProMD

Very interesting.

In all the cases I have serviced, cleaning and reassembling the parallelogram pins and bushings has brought the RD to normal function. This matches the corriente with SRAM’s MTB RD’s which sometimes become lazy shifting to the smaller cogs and cleaning the pins and bushings bring back the original performance. Clearly the spring can’t overcome the friction that builds up in dirty bushings.

I think off-axis stresses play an important role here also. Todays “dropped parallelogram” RD’s (a SunTour concept born with the first slant parallelogram RD in 1964) put substantial off-axis stresses in the pin-bushing units as opposed to the old style “Simplex/Campagnolo” in line parallelogram derailleurs.

I think Sram use of Igus bushings could not be ideal for this application. They’re not stiff enough and are not sealed properly.


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Darceking
Posts: 206
Joined: Fri Feb 28, 2014 1:48 am

by Darceking

without reading the rest of this thread. Brother had this happen, just took it to the shop and SRAM replaced it no questions asked

tanbrett87
Posts: 13
Joined: Wed Apr 22, 2020 5:01 pm
Location: Your Local River in the US

by tanbrett87

I had this happen on a 4 month old purchase last summer. I ended up bending a link in my chain during a race because of it.

I took it to my LBS, had some back and forth with SRAM then they finally did a warranty replacement. It's been good ever since.
@tanbrett87
2016 S-Works Tarmac
2019 Felt IA2 Disc
2019 Cannondale SystemSix HI-MOD (building)

b5000
Posts: 17
Joined: Tue Sep 05, 2017 6:15 am

by b5000

Very impressive that Jugi was able to disassemble and troubleshoot his Derailleur. Also really fascinating to see the internals and circuit board setup.

I was just glad to get mine warrantied and back quickly so I can keep riding. Sram sent a replacement very quickly.

dkeane123
Posts: 2
Joined: Wed May 06, 2020 2:50 pm

by dkeane123

Thank you all for this information, was very helpful. I was/am having the same issues. So I took the RD off and attempted to remove the pins from the bushings, but was unsucessful. I did not want to hammer on it with too much force, as I believe I will be able to get this replaced under warranty. Any thoughts on how difficult it was to remove those pins?

I should note that after my attempt and having the RD run back and forth a few dozen times through the gears, it now works flawlessley for the past 2 Zwift sessions. So clearly me hammering on it and exercising the RD freed the pins up in the bushings.

I am now going to be on my 3rd or 4th RD with this warranty, wondering if anyone has any ideas on maintaince that I could do to keep this from happening? I take the chain off monthly for cleaning and lubrication, so that would be an opportune time to get at the RD too. Thank you all.

Jere
Posts: 64
Joined: Sun Aug 07, 2011 5:35 am
Location: York Pa

by Jere

b5000 wrote:
Fri Apr 10, 2020 8:02 am
Unfortunately, I experienced the same issues with a new 11 speed eTap wifli RD. My RD was exhibiting the same issues that are described in this thread - exactly like this video: https://www.youtube.com/watch?v=Qsz6Rz8_-Uw. The entire new eTap group was installed on a new R5 disc frameset and I had put about 680 miles on it - having only assembled the bike in late January of this year. RD was never damaged by any crashes or strikes on the RD cage or body & the hanger is straight, bike & groupset are both essentially new (gearing setup is 50/34 and 11/28). When it initially stopped shifting mid ride, I thought it was a dead battery - so I swapped the FD & RD batteries and that fixed it for about 5 mins then it stopped again. When I got back home and put it on the work stand and tested it with the chain on and without: EXACT issues as described by this thread and the video to a tee.

I contacted the shop where I bought the groupset and described the issues and they promptly sent me a RMA number for a warranty exchange and arranged to send me a replacement. All of this was handled very promptly and professionally by the vendor and I had a replacement within 9 days (received it today and promptly installed it on the bike).

I strongly suspect that there is an issue with the internal servo mechanics - probably a small internal part failed inside the mechanism. I won't speculate but this is common in other complex mechanical parts like fan impellers etc. I also suspect that SRAM knows about this and that this failure is very common for the 11 speed eTap RDs. I suspect that they have addressed this in the new AXS groupset - but alas on top of it being more expensive; I don't want or need it.

Fingers crossed that this replacement RD has no issues going forward as I really enjoy eTap so far & don't want to change to mechanical or another groupset.

Anyone else run into this issue with 11 speed eTap RD?
Hi
Your dilemma sounds exactly like mine New R5 Disc new group about a 1000 miles very limited rain time.
Waiting for the return process. 2 E Taps Systems in use not real happy.
Over 100,000 miles on Di2 two batteries and tore wires , one faulty controller at handle bar.
I have replaced pulleys but that's wear and tear.
Rain bikes , every day bikes , race bikes they still have the original 10 speed UlTegra derailleurs.
Signed
Grumpy Old Man

b5000
Posts: 17
Joined: Tue Sep 05, 2017 6:15 am

by b5000

Jere,

yes its a bit of a shame for a otherwise very good groupset. Luckily SRAM and the retailer I bought the groupset from were very prompt and responsive in getting me a replacement. I'm interested to hear your experience once you get your replacement up and rolling. So far I've put about 450 miles / 724 km on the new derailleur and so far its been trouble free - hope it stays that way.

dkeane123
Posts: 2
Joined: Wed May 06, 2020 2:50 pm

by dkeane123

b5000 wrote:
Thu May 07, 2020 8:03 pm
Jere,

yes its a bit of a shame for a otherwise very good groupset. Luckily SRAM and the retailer I bought the groupset from were very prompt and responsive in getting me a replacement. I'm interested to hear your experience once you get your replacement up and rolling. So far I've put about 450 miles / 724 km on the new derailleur and so far its been trouble free - hope it stays that way.
I am in the process of replacing my third RD. Will be my 4th. Went through 2 in one year. This is the only place where I've also heard this issue, so I'm assuming just bad luck on my part.

wongp
Posts: 11
Joined: Tue Jan 14, 2020 5:15 am

by wongp

I didnt think this problem would be that widespread on the wifli but I guess was very wrong. I was hit with this yesterday and found this is completely a safety hazard as I've experienced exactly what was described in the first post of this thread.

This is the equivalent to VW's DSG neutral issues. This should really be a recall as it's potentially an accident waiting to happen when riding out of saddle up a pinch or climb.

I'm currently engaging the shop I bought the groupset. Not going to be quick process given the whole COVID situation.

I should have just stuck with Shimano. Doh.

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