I have difficulties installing Schwalbe Marathon Plus tires (ETRTO 622-28 700x28C) on Jalco DRX-20 rims (16-622). If I am reading the Sheldon Browns tyre sizing guide correctly, this is not a problem with tire width. I've tried this technique but tire is to stiff to install it without a levers. Last time I did it I broke two composite levers, this time I pinched two tubes. Previously I had a slightly wider rim (perhaps 18-622, don't remember exactly) and while it was a little tricky to put them on, it was still do-able even with no levers, whereas now I start thinking it's impossible. Is there any other trick how to put the tire on the rim? Could width be a factor in how difficult it is to fit? I'd be grateful for any advice.

I am having difficulties installing Schwalbe Marathon Plus tires (ETRTO 622-28 700x28C) on Jalco DRX-20 rims (16-622). If I am reading the Sheldon Browns tire sizing guide correctly, this is not a problem with tire width. I've tried this technique but the tire is too stiff to install it without levers. Last time I did it I broke two composite levers, this time I pinched two tubes. Previously I had a slightly wider rim (perhaps 18-622, but don't remember exactly) and while it was a little tricky to get them on, it was still do-able even without levers, whereas now I am thinking it's not possible. Is there any other tricks for how to get the tire on the rim? Could width be a factor in how difficult it is to fit? I'd be grateful for any advice.