pwa wrote: ↑28 Jun 2022, 9:19am
rareposter wrote: ↑28 Jun 2022, 8:57am
pwa wrote: ↑28 Jun 2022, 7:31am
Di2 would interest me if I thought that it might last 20 000 miles without an expensive component needing to be binned and replaced. I'm not getting the feeling that that would be the case.
There's no reason (barring crashes) that it should be any less durable than mechanical - in fact there are far fewer moving parts than mechanical so in theory, it should last a lot longer and it can also be much more sealed against the elements as there's no need to have cable access ports.
The STI unit is two small electrical switches, no different to a light switch or TV remote control. Compared to the cable pulleys and indexing clicks in a mechanical STI unit, there's far less in there.
The mechs have a tiny motor in them, no different to the motors in a car window mechanism but they're sealed units as well. There's really very little to go wrong.
Cassette and chainrings should arguably wear less than mechanical as the shifting is always better and crisper and cleaner and shifting under load is less of an issue.
Go on. I'm weakening!
To be fair, the reliability I have at present is down to me abandoning Ergo / STI years ago and using bar end levers instead. Most roadies won't do that. So they will compare the reliability of Di2 with STI levers, which I have found to be dire. I genuinely hope you are right and that Di2 turns out to be "fit and forget" in the best sense.
I'm a novice Di2 user so ..... . Nevertheless, I
am looking for "advantages", naturally; still noticing the disadvantages too, though.
I've just fitted a different chain (stainless steel Connex) and big chainring (46 instead of a 50) so I've had to move the front mech and re-adjust. This is much easier to do with a Di2 mech than with a mechanical equivalent.
For a start, it will go down the frame mounting to be the right height for a 46 ring, which can't be done on any mechanical front mech I've had on road bikes with a direct mount to the frame, over the years.
Secondly, there's only one adjusment screw needs fiddlin' with - the outward throw limiter. In big chainring & small sprocket, this screw needs screwing so that the cage outeris 0.5 - 1,0mm away from the big chainring. Everything else auto-adjusts.
The front mech auto-trims as the back gearing is changed. No need for difficult to set-up trimming clicks at the lever. Although I can set up such trims and other adjustments successfully - even with a triple chainring, mech and STI lever, although it takes a good while and a lot of fiddlin' - I know that this is no easy task, especially for a novice.
(Incidentally, using a non-indexed friction lever of downtube or bar-end kind, is no easy thing for many novices to learn either).
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Another perceived advantage is that the chain is always properly centred on the cogs; chain rubs are automatically avoided. For example, the rear mech won't allow either of the smallest two sprockets to be selected when the small ring is selected. The rear mech automatically moves to the third smallest sprocket, if in one of the two smaller sprockets, when you change from big ring to small ring. And semi of full-synchro settings can perform similar "perfect the gear ratio" style operations.
Such things, as you say, can be achieved "by hand" with non-indexed mechanical systems - but it's a skill that takes a lot of learning-by-practice; and we can still get it wrong. I recall the almost constant need, in group riding pre-1980-summick, to get the lad in front to trim his clattering rear mech as the chain threatened to climb or drop from it's poorly-selected sprocket.
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So some advantages, then. And if the Di2 is resilient enough for the mechs and levers to last 20,000 mile .... well, I might be dead before then! If not, I will moan, gripe, whine, complain and generally make every unhappy noise I know about "this new-fangled rubbish".
Cugel
“Practical men who believe themselves to be quite exempt from any intellectual influence are usually the slaves of some defunct economist”.
John Maynard Keynes