tafi said:
Evidence of such "undoubted" compromises would be welcome. I've used plenty of off brand chains (as well as "off-speed" chains - usually out of sheer curiosity) myself without a problem. I know of others who frequently prefer to use a campagnolo chain on an otherwise shimano drive train. The only "compromise" I can see here is that the cassette will probably wear out before the chain does.
Statements about curiosity aside, I will qualify what I said above and agree that it is usually best to use an OEM chain (if nothing else than for warranty reasons), but a subsitiute is usually also insignificantly different.
The width of the chain is far from the only factor which influeces FD shifting. Your claim of 0.1mm having an effect would be fine if a bike were a precision machine, but it clearly isn't. Indexing tolerances are more likely to be 0.5mm (maybe more) whilst BB tollerances for width are of the order 0.5mm~1mm and frame allignment tollerances are around 3-5mm (so that the chain line may vary by this ammount).
To say that 0.1mm (or even 0.5mm) difference in chain width is the deciding factor in shift performance is wishfull.
FDs can usually cope with these sorts of tolerances and mis-alignments standing on their head so a fraction of a mm (thats the difference between 9 and 10) isn't likely to cause problems and what I've seen bares this out in practice.
Moreover, when campagnolo adopted the UN chain, chain width decreased by 0.2mm without any change in other components. One was usually able to adopt the new chain without even having to retune the FD.
I have also seen OEM shimano 10 speed bikes fitted with older generation (9 speed) FDs to save money (usually becasue the manufactrurer was overstocked with that derailleur type). Shift performance was entirely adequate.
Well, I'm NOT saying that the shifting wouldn't be "entirely adequate" if you used a randomly chosen chain on a Double crankset ...
I would hazard to guess that despite the numerous bikes you've worked on, few-if-any had Triples ... and, on those that did you did not change the chain to one of your random choice ...
Because, it if you chose & installed the wrong chain on a Triple then you would quickly find that shifting across all three chainrings would be problematic.
If you are in doubt that the shifting becomes problematic, then the next time a bike with a rare, 8-speed Shimano Road Triple comes in, then put a 9-speed chain on it and see who well the combination shifts, or doesn't ...
Or, put a 10-speed chain on the next 9-speed Shimano Road Triple which you happen to come across ...
Et cetera.
Now, what I've described is the WRONG chain
type, but it illustrates the point on chains where the difference in the width of the chain is fairly small -- fractions of a millimeter.
And, indeed, there is wiggle room (
aka "imprecision") with a Double, but a simple extrapolation of what can occur with the Triple [
on a bike with non-Campagnolo shifters] to what may occur with the Double should indicate to you/anyone that the imprecision which you are introducing into the shifting by using too narrow OR too wide a chain is not enhancing the shifting, but rather diminishing it ...
With too narrow a chain, and the dis-/engagement may be balky ...
With too wide a chain, and the rider will probably need to trim (if possible) sooner rather than later.
A lot of drivetrain combinations work which are not
authorized by Campagnolo, Shimano, SRAM ...
AND, I'm a big advocate of NOT adhering to the "company line" when it comes to maintaining continuity with components, BUT your remark was too casual (at least, IMO) & you thereby opened a can of worms which was best left unopened by the average cyclist ...
So, while you might use a 9-speed Shimano chain on a 9-speed Campagnolo drivetrain, I don't think you would want to use the wider 9-speed Campagnolo chain with a 9-speed Shimano drivetrain because of the fore mentioned probability of needing to trim sooner-rather-than-later
(heck, you may/must know that some people NEVER trim their front derailleur after shifting from one chainring to the other on bikes whose shifters are capable of trimming the front derailleur AND SO installing a chain which is fractionally too wide would only aggravate the situation).
