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Di2 Failure mode

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quixoticgeek:

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

Brucey:
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

grams:
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:

--- Quote from: grahamparks on 13 May, 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.

--- End quote ---

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.

Jakob W:
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...)

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