JDub
I noticed that Campy H11 cranks say they are optimized for 142 rear spacing.  I think the chainline is offset about 2.5mm outward.  I have read that optimal chainline for 130 is 45 - 45.5mm, and 46 - 47 for 142.

Is this a real world compatibility issue or planned obsolescence marketing?

Thank you,
Jdub
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drwelby
135 and 142 are the same chain line. The 142 thru axle is just longer because it has to fit in the recesses in the dropout. Without them your dropout would be a dropup.

The extra offset is compared to a standard 130mm rear hub road chain line.
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JDub
correction made
Is the 2.5mm offset truly significant? Or is it an OCD detail, which is nice but may not affect shifting performance or drivetrain noise.
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Volsung
Once you change gears your chain line is off anyway.  The h11 is probably better but I don't think it matters all that much.
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drwelby
2.5mm isn't much but on some of the first custom road disc bikes people went with 135mm rear hubs and figured the difference wouldn't matter. But it turned out that if you ran short stays and big road-sized chainring the chain would 'ping' on the pick-up teeth in a lot of the smaller cogs when crossed over on the small ring. The components had been designed so that the chain would just barely clear with a 130 hub and that 2.5mm was enough to cause some problems.

There were some kooky workaround, namely Specialized's SCS hubs that were 135/142, but had a 130mm chainline. Groups that were released in the meantime seem to have a little more tolerance in the chainring department. On a gravel bike, with longer chainstays and smaller big rings it's less likely to be a problem. On a 1x bike there is no problem and some would argue that having a narrower chainline is better. But since we're talking about Campy I'm going to assume 1x isn't going to be relevant.
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oleritter
You guys nailed it!
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NoCoGreg
If the chain line is off it will be most obvious when cross chaining where one combination (Big-Big or Small-Small) will get better while the other gets worse.  I tend to ride in my big chainring most of the time so having a more usable Big-Big would be great for me.  If I'm in my small chainring I seldom use the smallest 3 cassette cogs.  But that's just me and I've got some very fast friends who seem to spend most of their time in the small ring so determining if a chain line offset is good or bad will depend on your riding style.
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