Trek 520 model changes during years What are main changes in Trek 520 during the years? I have possibility to buy new Trek 520 year 2015 for 1000 Eur and year 2018 for 1300 Eur. Is there right place to safe some money?

What are difference between 2017 and 2018 models?
The primary difference between the 2015 and the 2018 seems to be the availability of disc brakes. The decision will depend on how much you think the disc brakes will improve your ride quality. I would take both for a test ride and see if you can really feel the difference in braking quality. The discs may give you better braking in wet or muddy conditions especially if the bike is loaded for touring. A concern may be the availability of disc brake parts if you travel in very remote areas.