My Nomaad Mk II, I wanted the Q factor to be as close to the same as on my derailleur bikes as practical. I selected a square taper bottom bracket spindle about 10mm shorter than I should have for an ideal chainline, thus my chaineline is off about 5mm.
I did not think that would be a big deal, I am running my chainring on the inside position on a double crank. Running a bashguard on the outside. But if I found a chainline error of 5mm to be too big, I figured I could use the outer position on the crank for my chainring, that would have had an ideal chainline. Or I could have put a spacer on the right side of the bottom bracket to move the bottom bracket further to the right.
Now, eight years later, have not had a problem with a 5mm chainline error. I am running the threaded sprockets. Last year I finally flipped my sprocket for the first time. I see no reason to change my driveline to reduce chainline.
I have noted on this forum in the past I am running a 16T sprocket, not the Thorn recommended 17T. I cut a small notch in one tooth and always put a link with outer plates on that tooth, the reason I do that is described here:
https://www.sheldonbrown.com/chain-life.htmlWhat I am going to describe here is the difference in wear on the sprocket teeth with a chainline error. The chain links that have inner plates, those inner plates rub on the side of the sprocket teeth, the links with outer plates, those plates are physically further apart and to do not contact the sprocket teeth.
First photo, the sprocket after eight years of use. You are looking at the outer side of the sprocket, if the sprocket was still on the bike you would be on the right side of the bike and the hub flange and spokes would be behind the sprocket. Because my chainline at the crankset was narrower by about 5mm, the chain was slightly pulled inwards against the sprocket teeth as I pedaled. You can see the notched tooth, I always ran a link with outer plates on that tooth. The tooth to the immediate right of that tooth, you can see visible side wear on the side of the tooth, since that tooth always had chain links with inner plates, the plates on the chain wore down the tooth slightly.
Second photo, the other side of the sprocket. A very slight amount of wear on the side of the sprockets that had inner plate links, but not as much wear as the first photo shows.
Thus, there is a bit more wear on the sprocket teeth with the additional side wear when you have a small amount of chainline error, but in my opinion it is not enough to be of concern. That said, my chainline error is about 5mm, if you had significantly greater chainline error, that might start to be a bigger concern.
This is not much wear for eight years, but I have several derailleur bikes too and most of my distance is ridden on those other bikes. So far in 2021, I have not ridden my Nomad at all. That said, my Nomad was the bike I used in some of the more harsh conditions that I have been in.
One other note, you can see from the photos that the teeth that had inner plate chainlinks are smaller now, those teeth had more wear than the other teeth, that is due to every other chain link being slightly more elongated as described at the Sheldon Brown website that I cited above.
