I swapped out the outer chainring on my cyclocross bike for a Sugino 42T.
With a 42T, the tips of the front derailleur cage and the outer chainring teeth start to separate as you move toward the rear.
I call this "tooth clearance," and when it gets too large,
the derailleur cage doesn't push the chain at its optimal point during shifts,
so it's worth correcting if you can.
↑After correction
Since cyclocross bikes have a higher bottom bracket than road bikes,
the gap between the front derailleur cage and the chainstay got pretty tight.
No problems though.
Apparently the bike shop refused to install this chainring because it's supposedly incompatible with Campagnolo 11-speed (which is what this bike has),
but since the original FSA/Shimano 10-speed setup is already working for shifting,
I figured I could get it adjusted well enough to work without issues.
And indeed, I got it working properly.
If the reason for refusing is "it's outside the manufacturer's recommendations,"
then you shouldn't be selling complete bikes with third-party cranks or brakes on them either.
There are cases where something really is impossible no matter what, or where you might actually get hurt trying,
but if that's not the situation,
it's better to try and accommodate what the customer is asking for.
With a 42T, the tips of the front derailleur cage and the outer chainring teeth start to separate as you move toward the rear.
I call this "tooth clearance," and when it gets too large,
the derailleur cage doesn't push the chain at its optimal point during shifts,
so it's worth correcting if you can.
↑After correction
Since cyclocross bikes have a higher bottom bracket than road bikes,
the gap between the front derailleur cage and the chainstay got pretty tight.
No problems though.
Apparently the bike shop refused to install this chainring because it's supposedly incompatible with Campagnolo 11-speed (which is what this bike has),
but since the original FSA/Shimano 10-speed setup is already working for shifting,
I figured I could get it adjusted well enough to work without issues.
And indeed, I got it working properly.
If the reason for refusing is "it's outside the manufacturer's recommendations,"
then you shouldn't be selling complete bikes with third-party cranks or brakes on them either.
There are cases where something really is impossible no matter what, or where you might actually get hurt trying,
but if that's not the situation,
it's better to try and accommodate what the customer is asking for.