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

Discuss light weight issues concerning road bikes & parts.
BdaGhisallo
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Joined: Wed Mar 17, 2004 1:38 pm

by BdaGhisallo

CannondaleETAPwifly wrote:
Fri Nov 16, 2018 12:40 pm
I have a Cannodale Synapse Hi Mod disc ETAP which has had two replacement rear wifli derailleurs in 6 months due to poor reliabilty. When trying to change gear on the rear cassette nothing happens after pushing the lever then after a minute or so it might decide to change which is far to late as you barrel into a steep hill and cannot change down to an easier gear. The failures are random in occurence and duration. Luckily they have been witnessed by mechanics from a bike shop and friends I ride with. I believe the SRAM ETAP Wifli has a design fault. I have done all the usual things inluding new batteries all round but nothing fixes it other than a replacement wifli derailleur which will probably fail again.
And SRAM are about to launch a new generation of ETAP without, seeminly, addressing issues from the first generation....

by Weenie


Fisherfreerider
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Joined: Thu Sep 29, 2011 1:19 am

by Fisherfreerider

BdaGhisallo wrote:
Fri Nov 16, 2018 12:46 pm

And SRAM are about to launch a new generation of ETAP without, seeminly, addressing issues from the first generation....
Thats a bold statement considering nobody really knows anything about the new system....

BdaGhisallo
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Joined: Wed Mar 17, 2004 1:38 pm

by BdaGhisallo

Fisherfreerider wrote:
Fri Nov 16, 2018 3:10 pm
BdaGhisallo wrote:
Fri Nov 16, 2018 12:46 pm

And SRAM are about to launch a new generation of ETAP without, seeminly, addressing issues from the first generation....
Thats a bold statement considering nobody really knows anything about the new system....
Aside from replacing these defective Etap RDs under warranty, have you seen any public acknowledgement from SRAM that there is an issue with the current design?

Fisherfreerider
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Joined: Thu Sep 29, 2011 1:19 am

by Fisherfreerider

Why do they need to say anything? They are replacing them for free.

Monkeyfudger
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Joined: Thu Apr 11, 2013 7:26 pm

by Monkeyfudger

Are they, or are they replacing them under warranty? Drastically different.

BdaGhisallo
Posts: 2060
Joined: Wed Mar 17, 2004 1:38 pm

by BdaGhisallo

Fisherfreerider wrote:
Fri Nov 16, 2018 4:08 pm
Why do they need to say anything? They are replacing them for free.
How about they fix the issue so that customers can buy products that work and don't have to go through the warranty process? I wouldn't see SRAM knowingly selling faulty RD's but happily replacing them one after another under warranty as something that should please anyone.

If there's no acknowledgement of the issue with Gen 1 Etap does anyone have confidence that Gen 2 Etap won't suffer the same problem?

moonoi
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Location: Earth

by moonoi

But is it really a widespread problem? Personally I've not had issue with either the short cage or Wifli versions of etap over the past 2 years I've been using it.

Rather like Shimano failing to acknowledge there's an issue with Ultegra 6800 cranks failing, most likely in the grand scheme of things the failure rate is so low that there isn't anything to acknowledge publicly.

You're likely to get a skewed idea of how widespread the problem is, since the only people posting about it are those that have issues, whilst the many thousands of others are out there happily riding their bikes without issues, and have no need to post about how great it is.

Sent from my SM-G965F using Tapatalk


Fisherfreerider
Posts: 176
Joined: Thu Sep 29, 2011 1:19 am

by Fisherfreerider

BdaGhisallo wrote:
Fri Nov 16, 2018 4:38 pm
Fisherfreerider wrote:
Fri Nov 16, 2018 4:08 pm
Why do they need to say anything? They are replacing them for free.
How about they fix the issue so that customers can buy products that work and don't have to go through the warranty process? I wouldn't see SRAM knowingly selling faulty RD's but happily replacing them one after another under warranty as something that should please anyone.

If there's no acknowledgement of the issue with Gen 1 Etap does anyone have confidence that Gen 2 Etap won't suffer the same problem?
I think you are making it a much bigger issue than it is. Most likely it has already been fixed but it takes a LONG time for things like this to get out of the product stream.

mike
Resident Pro
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Joined: Tue Mar 18, 2003 9:42 pm

by mike

my eps record rear derailleur experienced similar issues. hasn't been fixed yet.

RocketRacing
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Joined: Thu May 10, 2018 2:43 am

by RocketRacing

Hmm. New etap owner here. Once and a while i will be riding and then “thunk”, something catches or shifts at the back, one gear only. Not yet sure what it is. Late shift? Randomness on the chain/casette.? Poor alignment and chain hopping cogs?

Never had miltiple shifts from what i could gather. But i will watch.

RocketRacing
Posts: 157
Joined: Thu May 10, 2018 2:43 am

by RocketRacing

Out of morbid curiosity, i just ran my system by hand. No rear shift issues in my few minutes of testing, but i paid attention to how the system operates.

If i shift when coasting, the derailer first moves, and the chain changes cogs when i pedal. Big deal right? Well, when coasting, the derailer only moves up to threee places, no matter how many times i hit the shift button (all shifting in same direction). So If you shift 5 times... the rd moves three places... and it will only do the last two movements/gears after you pedal. The system obviously knows not to let the rd go too far before the chain actually starts moving... but once the chain is shifting cogs the system will do all 5 shifts flawlessly. So it is a failsafe system.

I presume this same failsafe system is the one that is failing in the above reported cases. The rd will not shift because it is waiting for the chain to move... but it is not being allowed to move, because of the failsafe. then the sensor suddenly works, or the system realizes its error in telemetry, and shifts happen as originally intended.
Last edited by RocketRacing on Sat Nov 17, 2018 4:01 am, edited 2 times in total.

RocketRacing
Posts: 157
Joined: Thu May 10, 2018 2:43 am

by RocketRacing

In further testing, i spun my crank, and while coasting began to shift up, then down, repeat, rrpeat. I made sure to count my ups and downs and count the net difference in up vs down shifts. All while coasting.

Then i would move the crank to see the results of my “preshifting”.

After 30+ shifts up and down the system got it right every time. If i shiifted down 15 times in a row, and up once, it would land on the second cog... so i could not trick it.

I suspect it has no memory of every input per say, but an algorithm that takes your current gear and adds or subtracts numbers of shifts in each direction. If you shift too far (beyond casette capacity), it ignores those extra inputs. It won’t let me be stupid.

Again, i suspect the failures described with multiple delayed shifts are part of the system that detects/determines if it is safe to shift. Maybe it doesn’t allow the shift, because the system says it is not allowed... when really it is safe. Then... oops... it is ok to shift now and the pending shifts occur.

This would explain the videos of enabling the stalled shifts by pushing in on the deraileur.

RocketRacing
Posts: 157
Joined: Thu May 10, 2018 2:43 am

by RocketRacing

I do not think it is a rd (wifi) reciever issue. The issue is not that the rd loses track of where you want it to be, just that it fails to move. So the message gets there, but the response is just... at it’s own time.

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

by XCProMD

From my experience the problem is the RD becomes too stiff because of the pivots not rotating freely. That causes the system to protect itself, most probably when it detects the motor is drawing too much current (EPS and Di2 have this function too).


by Weenie


RocketRacing
Posts: 157
Joined: Thu May 10, 2018 2:43 am

by RocketRacing

That would make sense

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