Author Topic: Di2 Failure mode  (Read 18387 times)

quixoticgeek

  • Mostly Harmless
Di2 Failure mode
« on: May 13, 2018, 12:22:41 am »

Was discussing with a cyclist friend of mine the merits of electronic gear shifting, and whilst we both agreed the flexibility and extra options sound wonderful, it did get us both wondering about the failure mode.

With an old school cable based rear derailleur, it's relatively easy to bodge it into a single speed get you home mode.

With a Di2 RD, can you get it into the gear you want, disconnect all the cables/power, and ride it in single speed mode? What about the front derailleur?  What other unique failure modes are there to di2 shifting beyond the obvious of a flat battery?

How weather resistant is the Di2 kit? Will it take a pressure washer without bricking the electrics?

Thanks

J
--
Beer, bikes, and backpacking
http://b.42q.eu/

Re: Di2 Failure mode
« Reply #1 on: May 13, 2018, 07:55:20 am »
anytime you make a system more complicated, you introduce more failure modes. There is no way of avoiding this.  Given that one cannot see electrons flowing, diagnosis (esp of intermittent faults) is what a chum of mine refers to as 'crazy-making'.

Some of the common Di2 faults are not as you might expect; for example the ultegra 10s Di2 FDs often seized up and then the motor was strong enough to break the arm on the mech.... ::-) .  You couldn't buy a replacement FD of the correct type for love nor money, soon after the groupset was current. Newer FDs are not compatible with this system, so shimano's proposed 'repair' for this fault is that you buy pretty much a whole new groupset.... ::-)

Bowden cables are potentially troublesome too; in systems that are naturally neglected (such as IGHs on commuting bikes) they cause a deal of trouble and one would expect a reliable electronic system to be appealing. Yet it is often possible to buy Di2 alfine hubs more cheaply on ebay than the standard ones. In this incarnation, it seems it is either unappealing or unreliable, possibly both.  I have seen several systems scrapped because it stopped working and couldn't easily/economically be fixed.  In the distant past shimano tried before with an electronically controlled nexus 4 hub; it had an auto mode and everything. Pretty much sank without trace...


If professional cycle mechanics cannot make the system 100% reliable in use  then it probably isn't worth a light, yet it appears to cause a significant number of bike failures in professional races. I started to keep track of these when watching live coverage of various cycling events (they tend to edit them out of highlights; it is embarrassing when the race outcome is altered by an avoidable bike fault) but I soon got bored of this; it turned out that there wasn't often a professional bike race where no-one needed a bike change 'cause their poxy gears had stopped working...

They have tried their best with Di2 to make it weatherproof and easy to use/install/maintain but at the end of the day it is arguably a needlessly complicated sledgehammer to break a rather flimsy nut.

It rather reminds me of a gadget described by Douglas Adams in one of his books (and I paraphrase); "the feeling of achievement you get from making it work at all completely blinds you to the utter pointlessness of it...."

cheers


Re: Di2 Failure mode
« Reply #2 on: May 13, 2018, 11:53:44 am »
In answer to thre actual question, they stop where they are and can’t be moved. This can be either better or worse than a mechanical system (which dump you on the highest rear sprocket), depending on where it stops.

The biggest flaw in Di2 is the wiring and the unnecessary complexity. The wiring feels the same as a cheap audio cable - I was hoping they’d have hardened them  in some way, especially given they’re £10-20 each!

The Di2 system splits the smarts between a memory chip in the battery, a chip in the A junction and the rear mech. e.g. if you have a shifter, a battery and a mech connected through a dumb “B” junction, it won’t shift. Or if you want Bluetooth you need a new battery with more memory!

The SRAM wireless system which has exactly four components (two shifters, two mechs)  each wth their own battery, which seems a much neater solution, though obviously it has its own downsides, and is currently much more expensive.

Kim

  • Timelord
Re: Di2 Failure mode
« Reply #3 on: May 13, 2018, 04:12:00 pm »
In answer to thre actual question, they stop where they are and can’t be moved. This can be either better or worse than a mechanical system (which dump you on the highest rear sprocket), depending on where it stops.

The lack of somewhere to shove an allen key and twiddle it to your single-speed gear of choice seems like a serious omission.

Some years ago, a rider on the Exmouth Exodus (a ride with weather that's like the Star Trek movies; only the even numbered ones are good) had problems where water got into something and the system shifted to the smallest sprocket and then sulked.

On the other hand, I haven't heard many other cases of water ingress problems.  It's usually people forgetting to charge the battery.


Personally, I'd only bother with electronic gears if I needed electrical switch gear controls for ergonomic reasons, wanted to run a mid-drive motor with a hub gear (it shifts better if the motor and gears are being controlled by the same system, and most of the disadvantages of electronics are moot on an e-bike), or wanted to avoid a particularly problematic bowden cable run on an unconventionally-shaped cycle.
Careful, Kim. Your sarcasm's showing...

Re: Di2 Failure mode
« Reply #4 on: May 13, 2018, 05:55:27 pm »
Isn't there a diagnostics mode where you can frob the rear mech into a suitable position for your chosen sprocket and then leave it there? Sure I saw a ride report in another place where someone had done that (or maybe I misremember and they were bemoaning the lack of said mode...)

Karla

  • car(e) free
    • Lost Byway - around the world by bike
Re: Di2 Failure mode
« Reply #5 on: May 13, 2018, 06:05:25 pm »
AFAIK the front mech shuts down first, so all the power to the rear mech to get you home. 

Here's what I got when I did a web search for DI2 running out of battery.

Re: Di2 Failure mode
« Reply #6 on: May 13, 2018, 06:13:25 pm »
Isn't there a diagnostics mode where you can frob the rear mech into a suitable position for your chosen sprocket and then leave it there? Sure I saw a ride report in another place where someone had done that (or maybe I misremember and they were bemoaning the lack of said mode...)

That sounds an awful lot like normal shifting mode! If you’ve still got battery power and working comms then you don’t need a special mode to move the mechs. What it lacks is any way to move the mechs after either of those things fail.

Re: Di2 Failure mode
« Reply #7 on: May 13, 2018, 06:20:10 pm »
Some years ago, a rider on the Exmouth Exodus (a ride with weather that's like the Star Trek movies; only the even numbered ones are good) had problems where water got into something and the system shifted to the smallest sprocket and then sulked.

It sounds like maybe they triggered crash protection mode? That (somehow) disconnects the motor from the cage which then jumps to the smallest cog. It can be reset by holding down the index adjust button for 5 seconds. It’s likely not every Di2 user knows this exists.

Re: Di2 Failure mode
« Reply #8 on: May 13, 2018, 06:43:54 pm »
Isn't there a diagnostics mode where you can frob the rear mech into a suitable position for your chosen sprocket and then leave it there? Sure I saw a ride report in another place where someone had done that (or maybe I misremember and they were bemoaning the lack of said mode...)

That sounds an awful lot like normal shifting mode! If you’ve still got battery power and working comms then you don’t need a special mode to move the mechs. What it lacks is any way to move the mechs after either of those things fail.

No, I think this was something along the lines of being able to manually move the mech to the desired position and then lock it, but of course I can't now find the discussion thread...

zigzag

  • unfuckwithable
Re: Di2 Failure mode
« Reply #9 on: May 13, 2018, 06:52:15 pm »
one rider had to abandon the tcr as the rear mech's cable disconnected inside the frame (wasn't properly inserted?) which necessitated removal of bb30 bb, and with no bike shops open this was kinda showstopper. usually di2 works fine, but when it doesn't it can be a real pain to fix.

Re: Di2 Failure mode
« Reply #10 on: May 13, 2018, 09:26:38 pm »
one rider had to abandon the tcr as the rear mech's cable disconnected inside the frame (wasn't properly inserted?) which necessitated removal of bb30 bb, and with no bike shops open this was kinda showstopper. usually di2 works fine, but when it doesn't it can be a real pain to fix.
That is more a problem of poor access to mission critical components; it could have happened with some mechanical gear cabling (or indeed brake or light cabling which would have been much more of a showstopper. Hard to singlespeed your brakes!). This is why I have always been unhappy about a lot of internal routing. Di2 wiring may be more fragile; this is not necessarily a showstopper with a decent approach to installation. Note I am still not a fan of bike electronics and am well capable of killing bike computers with a single glance.

jiberjaber

  • ... Fancy Pants \o/ ...
  • ACME S&M^2
Re: Di2 Failure mode
« Reply #11 on: May 14, 2018, 09:31:05 am »
I’ve been running Di2 since 2015, in that time I’ve had 3 issues

1st, at 2AM I took a tumble down some concrete steps at Gatwick en route to Brighton on a FNRttC.  (April 2015) We collectively spent 45 mins trying to fix the issue including a lot of helpful googling for crash protection etc.  The issue turned out to be the right shifter having taken a whack and rotated on the bar had pulled out the cable, once reconnected I was back on my way.

2nd issue was a pure mechanical one (2015 again), a chain quick link was far too worn to be in service and decided it wanted to depart.  The side plate snapped resulting in the jagged remains jamming in to the jockey wheel with the inevitable RD being dragged in to the spokes and destroyed.  Luckily this was on the way to the train station from home (on another FNRttC) so I was able to get home.  The parallelogram on Di2 RD is made of cheese so a new RD was required.

Final issue was earlier this week, the battery on a bike went from 100% to 50% in 30 km.  Quite alarming as I’m planning a 400km perm this week.  My current theory is that it might not have been at 100% in the first place – suspect the laptop it was charging off might have gone to sleep before it was fully charged.  I confirmed it was at 100% last night and it is still at 100% this morning, so keeping an eye on it….

In terms of waterproofness – well I’d say it worked pretty well through the jet wash conditions of Yadd Moss on LEL last year.  Here’s a fairly accurate ACME simulation (but with less water than we had!) https://twitter.com/ACME_Essex/status/911531999244013568

You get plenty of warning of low battery, helped even more if you have the ANT+/BT connection running and can see the battery charge on a Garmin or similar head unit (charge is shown in steps of 10 from 10 to 100%) or if you have the BT unit, you can also use an app on the phone.  On low battery, the FD stops working and there’s probably ‘a good chunk’ of shifts remaining on the RD.  I have never got myself in to that position from memory (though might have had it once in 2015?)

I charged the system once on LEL sometime after St Ives (I think) as a precaution (I think it might have been down to 30%?)

In terms of on ride bodges – as Kim has pointed out – they missed a trick having some sort of physical position adjust in the event of lockout.  I’ve never had the crash protection kick in so no idea on what the RD does when that happens other than it stops working!

If it all stops, you are still left in some gear – just it might not be the one you need.  2 alternatives there, one, stay in that gear and work at it….

Or more drastic would be to drop some links out of the chain, bypass the RD and select a desired gear.  The latter being no different to if a mechanical RD snapped off of which I have seen lots of times on other’s bikes…. Only drawback here would be if you are running oval chainrings this option might not work.

All these systems have their pros / cons to weigh up when deciding what's right and I can't remember the last time I saw a thread entitled "In praise of $type gear shifting system"  :thumbsup:
Regards,

Joergen

Re: Di2 Failure mode
« Reply #12 on: May 14, 2018, 10:12:26 am »
Option 3 is carrying an old mechanical mech with a pre-inserted extra-long limit screw. I might do this on BCM.

(I considered doing the same for LEL when I had mechanical gearing, so this isn’t necessarily a Di2 thing)

My cables are long enough that they’ll run from the battery and rear mech to the handlebar junction with no internal joins (I’m running 1x). I do currently have an internal junction so that the left shifter also shifts the rear, but thus far it’s of limited usefulness, so it might go. The junction can come out through the front cable routing hole -  assuming I have the right tiny allen key to take the cable stop off.

citoyen

  • Occasionally rides a bike
Re: Di2 Failure mode
« Reply #13 on: May 14, 2018, 10:15:51 am »
Final issue was earlier this week, the battery on a bike went from 100% to 50% in 30 km.  Quite alarming as I’m planning a 400km perm this week.

If you've got room in your saddlebag to carry the charger cable, it's worthwhile - doesn't take long to top up the battery from a USB power pack.

simonp

  • Omnomnomnipotent.
Re: Di2 Failure mode
« Reply #14 on: May 14, 2018, 10:37:10 am »
I've had serious issues with mechanical cabling on Paris-Brest-Paris. Cable broke inside right shifter. Could not remove the cable.

Let's say my right shifter failed with Di2. I'd use the Shimano app to reconfigure the left shifter to do everything.


mattc

  • n.b. have grown beard since photo taken
    • Didcot Audaxes
Re: Di2 Failure mode
« Reply #15 on: May 14, 2018, 10:37:36 am »
All these systems have their pros / cons to weigh up when deciding what's right and I can't remember the last time I saw a thread entitled "In praise of $type gear shifting system"  :thumbsup:

Did you miss the reports from the LEL mechanics? At least one recommended DT shifters for long events [for reliability].

People are still upset about that post 8 months later ...
Has never ridden RAAM
---------
No.11  Because of the great host of those who dislike the least appearance of "swank " when they travel the roads and lanes. - From Kuklos' 39 Articles

simonp

  • Omnomnomnipotent.
Re: Di2 Failure mode
« Reply #16 on: May 14, 2018, 10:52:55 am »
The obvious answer is to go fixed wheel.

A freewheel is too much risk, what if the pawls stuck?

Samuel D

Re: Di2 Failure mode
« Reply #17 on: May 14, 2018, 12:08:57 pm »
The obvious answer is that everyone is different. Some think Di2’s “flexibility and extra options sound wonderful”. Others cannot figure out what conceivable extra options would be desirable for shifting gear.

Some think moving their arm to a down-tube shifter is too onerous to seriously contemplate. Try reaching the cup of coffee on your desk right now. Who would put up with that on a bicycle?

I love Jobst Brandt’s sarcasm about shift-button placement here. Ha ha!

We’ve arrived. If it fails, call a tow truck.

Despite my grouchiness I’m curious about all forms of cycling culture and so sometimes read the cycling subreddits on reddit. It’s another world out there and there are more ways to break Di2 than you would readily believe.

Re: Di2 Failure mode
« Reply #18 on: May 14, 2018, 12:49:11 pm »
I've had serious issues with mechanical cabling on Paris-Brest-Paris. Cable broke inside right shifter. Could not remove the cable....

that is arguably just poor maintenance. Bowden cable inners don't last forever; in most STI units they will fail by fatigue. Courtesy of a chum of mine who has very regular riding habits, I can tell you that all the cables he tried would last about 150000 shifts before they were likely to fail by fatigue. This may vary with tension required and the cable type. 

These days he just replaces them every six months (which for him is about 130000 shifts), because (as you have discovered) a cable which has been frayed for a while and then breaks is very difficult to remove.

Most folk just inspect the cable (where it bends most in the shifter) once every couple of weeks and as soon as they see one broken strand it is time for a new one. With most 'washing line' STIs this is easy enough but with some others it is less easy in which case a routine replacement approach is probably better.

FWIW I evaluated the design of bicycle gear and brake cables vs those used in industrial wire ropes which are required to last (say) 500000 cycles or more  without fatiguing, and

a) there was no way they were anywhere near that level of fatigue resistance and
b) there was no way they ever could be; the sheaves (pulleys) and bend radii in bicycle parts could never be small enough to provide an infinite fatigue life.

Thus Bowden cables are consumables, just like tyres are, but their symptoms of failure and expected life are different.

cheers


Kim

  • Timelord
Re: Di2 Failure mode
« Reply #19 on: May 14, 2018, 12:51:50 pm »
I've had serious issues with mechanical cabling on Paris-Brest-Paris. Cable broke inside right shifter. Could not remove the cable....

that is arguably just poor maintenance.

Or insufficient paranoia.
Careful, Kim. Your sarcasm's showing...

Re: Di2 Failure mode
« Reply #20 on: May 14, 2018, 12:52:44 pm »
Di2 is a mass market product, not a niche device for the 0.0000001% of cyclists who ride PBP or LEL. However, if you are prepared to accept the possibility of non-roadside repairability and that you have to charge a battery every 1000 miles then you have an otherwise maintenance free system that is a delight to use not least because it require little physical effort.

To my surprise, one of the most annoyingly fatigued parts of my body on a hilly 1000k was my hands from constantly operating the 'positive' action of Campag ergos.

Sure there are downsides to everything, and you just have to weigh up the pros and cons.

Kim

  • Timelord
Re: Di2 Failure mode
« Reply #21 on: May 14, 2018, 01:02:59 pm »
Di2 is a mass market product, not a niche device for the 0.0000001% of cyclists who ride PBP or LEL. However, if you are prepared to accept the possibility of non-roadside repairability and that you have to charge a battery every 1000 miles then you have an otherwise maintenance free system...

Quite.  An awful lot of that mass market are the people who can't diagnose or adjust mechanical indexing properly, and whose roadside repair strategy is a mobile phone.  Electronic shifting has a significant advantage there, as it's all about MTBF rather than repairability.


Quote
...that is a delight to use not least because it require little physical effort.

To my surprise, one of the most annoyingly fatigued parts of my body on a hilly 1000k was my hands from constantly operating the 'positive' action of Campag ergos.

I think that's one of the best reasons to use it.  I like MTB thumb shifters, but I do get thumb pain from their prolonged use.  Avoidable with different types of shifter, but they have other compromises.
Careful, Kim. Your sarcasm's showing...

simonp

  • Omnomnomnipotent.
Re: Di2 Failure mode
« Reply #22 on: May 14, 2018, 01:17:56 pm »
I've had serious issues with mechanical cabling on Paris-Brest-Paris. Cable broke inside right shifter. Could not remove the cable....

that is arguably just poor maintenance.

Or insufficient paranoia.

Indeed. It was my first bike with STI drop shifters and no-one had told me the cable wear rate would be far higher than anything I'd experienced before. It's the first time I've ever had a gear cable fail while riding.

I got round the ride, but it caused a significantly increased amount of sleep deprivation while I got it fixed.  I had none of these problems riding fixed in 2011 or 2015! Only mechanical issue I had was having to move the rear wheel back slightly due to chain wear after about 900km.

Most of the tales of woe with Di2 I've heard about are to do with flat batteries. A flat battery is a far easier fix than a gear cable broken inside an STI shifter, and avoiding it in the first place is also far easier.

I've done full circle in that I'll go from STI to fixed and then Di2 across 4 PBP editions, assuming I CBA to get qualified and ride next PBP.

Re: Di2 Failure mode
« Reply #23 on: May 14, 2018, 01:33:26 pm »
if Di2 systems were well engineered to have a good MTBF and folk wanted/got that, along with improved ergonomics etc, then I would expect Alfine Di2 to be more popular than it has been; the potential customers for that technology are arguably the least likely to attempt a roadside fix etc. and most likely to be tempted by gadgets.

I agree that most failures are to do with batteries but as I mentioned above, no complex system has a single failure mode; it will have many. Sooner or later one will catch you out and then you will be quite stuck; in the short term because you (in fact no-one) can fix it by the side of the road, in the longer term because the planned obsolescence inherent in such systems means you won't be able to buy spares for it.

To me,  it represents the exact antithesis of the sort of technology that ought to be incorporated into a simple machine such as a bicycle.

cheers

Re: Di2 Failure mode
« Reply #24 on: May 14, 2018, 01:46:51 pm »
Don't buy it then.

Simples.