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Doesn't look to be too different from the driveside. But yes, that chain isn't going onto the front chainring directly, no way. If it looks like a duck... Quack!
possibly related (specifically section 6C):
https://wheelbased.com/2020/12/24/bicycle-rear-suspension-by-specialize…
As I've mentioned, narrow wide chainrings and derailleur clutches helped here and a lower idler will prevent more or less all of that (and Loic is running one), but yeah, it's something to consider when it comes to trail bikes maybe.
I agree with you that there is a lot less chain wrap. I'm just saying that you have to look at it a bit differently due to the fact that there is an idler in play. I'm not suggesting that this fully discounts any concerns over the lack of chain wrap, I'm just saying that 1/4 wrap with an idler is a lot different than 1/4 wrap without one, so you shouldn't draw the same conclusions between the two bikes. I spent a good 4-5 months on an idler bike...not under DH type conditions, but still riding it fairly hard, and dropping the chain was never an issue. Was it better or worse than a "regular" bike? No idea. I just know that the addition of an idler totally changes the way the chain acts around the chainring.
I see your point about the idler being forward and this causing less wrap than other idler systems. But what are we talking about? A tooth or two? From a super blurry screen shot? Who the hell knows.
My interpretation is that you're comparing 2 very different things.
1 - Classic setup - Chain wrapped roughly halfway around a chainring. Lots of chain flapping in the breeze.
2 - Idler - Chain wrapped roughly a quarter of the way around a chainring. An idler, also with chain wrapped a quarter of the way around the thing.
There you go. Two very different things, that act in very different ways. All I'm saying is that you can't really directly compare these two things to one another and only consider one part of it. You can't say "the idler bike has less chain wrap, so it's more likely to drop a chain." It may very well be more likely to drop a chain, but the addition of the idler totally changes the equation. So making an argument solely based on chain wrap is a bit of a mistake. You shouldn't look at an idler bike and say "that has way less chain wrap than my bike, so you're probably going to drop a lot of chains." There's way more to it than that.
Like I've said a few times...I'm not saying that it isn't a factor, I'm just pointing out that there's a lot more to it than just chain wrap. The idler completely changes the way that the chain interacts with the chainring.
My point is that with or without an idler, the part of the chain from the chainring to the rear derailleur is the same. Having an idler or not having it will have no effect on that part, so the chain will flop around exactly the same. Therefore if it does (and it does) flop around, it can start unwrapping itself or just start to do it, then the rider backpedals aaaaand... with less than 1/4 of chainring wrap, you throw the chain off completely. Not so, when half the ring is wrapped.
And having 1/4 of the ring wrapped is the same, regardless if the chain is directed to the ring from an idler or something else. The factor with what the chain will be doing is the length of the span to the next chainring (the longer it is, the worse of course) and whether it is taught (the power carrying branch of the chain - cassette to chainring for bikes, going over the idler if it is present) or not (the idle branch, so the chainring through rear derailleur to the cassette branch for bikes).
So yeah, it's the fact that you could have the chain miss the ring and the rider backpedal that could throw the chain off the ring MUCH sooner on an idler bike compared to an idlerless bike. But that whole point is moot once you have a lower guide pulley, which Loic has.
What causes a chain to derail? When does it happen? I would say one of the main causes would be the long, unsupported length of chain flapping around in the breeze. So, what have we done to reduce chain derailment over the last few years?
Increase Tension - Derailleur clutches. Certain old school chain tensioners.
Improve Tooth Retention - Tooth profiles. Increase wrap via certain chain retention systems.
Capture the Chain so it can't bounce off as easily - Old school MRP chain systems
Decrease chain movement - STFU
So, what happens when we add an idler to our system? We lose out on one front (chain wrap), but we improve on another (chain movement). An idler takes what was once one, long unsupported chain, and it creates two, most likely shorter, lengths of chain. It's similar to what you would get if you put a guy wire on a long stretch of unsupported cable. That short section of chain between the idler is just not going to bounce around as much as a classic, non idler drivetrain. Again, I'm not saying it's better, just different. In fact, what an idler probably does is move the most likely point of derailment from the chainring to the idler. You see lots of guide systems on the idler, as now you have a (relatively) longer stretch of unsupported chain bouncing around between the idler and the cassette. Most bike companies seem more concerned with this point, than at the chainring. How the chain interacts with the idler is at least as important as how it interacts with the chainring.
Anyhow, that's it for me. If you can't admit that a chain with and without an idler are two different things, and act differently, I don't think I can convince you otherwise. Again, I'm not trying to argue that an idler is better or worse, I'm just pointing out that it is different, has different factors at play, and should be analyzed differently. I didn't think that was a very controversial idea.