Originally Posted by
rekmeyata
Those set screws are there to help take up chain slack, in other words to set the chain tension. The tension should not be more or less than a half an inch when you push down on the chain in the center. Once you have the tension set correctly then you make sure the axle is aligned.
It took me a little while to find the CORRECT article on the internet that knew what they were talking about, because I can't explain how to set the screws without showing you, and I can't be there to do that. The internet had 2 pages of incorrect information as to what those screws were for. Without further ado please see:
Simple Ways to Adjust Horizontal Dropouts: 13 Steps (wikihow.com)
This is a reflection on that article, not you, but that's article seems to have been written in a way to almost deliberately confuse the inexperienced. It shows (and links a reference to) a bolt on axle while talking about quick releases, and then shows a wheel with a full cassette (and disc brake?) but no derailer when talking about single speed/fixed gear bikes. It's also referring to track ends, not horizontal dropouts like the OP's bike, though in this case the screws behave in a similar manner, at least for alignment purposes.
The OP's bike is a typical multispeed w/rear derailer bike, so there is nothing they need to do to set chain tension. Just get the wheel centered up, tighten it, and proceed.
Originally Posted by
smd4
How do you make this adjustment on a bike with vertical dropouts?
You don't. The upside of vertical dropouts is that if the frame was made properly to begin with you'll never need to mess with it. The downside is that it has to be done right from the start, and you can't run it as a fixie because there's no way to adequately tension the chain. Of course running fixed on a horizontal dropout isn't exactly ideal, but that isn't to say you can't/I haven't.