Joined: Nov 2006
Posts: 19,811
Likes: 596
From: NJ, NYC, LI
Bikes: 1940s Fothergill, 1959 Allegro Special, 1963? Claud Butler Olympic Sprint, Lambert 'Clubman', 1974 Fuji "the Ace", 1976 Holdsworth 650b conversion rando bike, 1983 Trek 720 tourer, 1984 Counterpoint Opus II, 1993 Basso Gap, 2010 Downtube 8h, and...
Welcome to the forums!
Where are you located? You'll find most of us are in the US and refer to the tires you mean as 700c rather than 28". And most of us shop online.
Schwalbe Marathons are pretty tough tires, but I don't know the specific ones you mention. There is a search function on Bike Forums, but most people have more success using Google search and limiting the results to this site; try that, if you know how, and you'll probably find a lot of information about Marathon XR tires.
Good luck!