Spring Spacers are available for John Deere 60, 90 and ProSeries openers, including the 1560, 1860, 1590, 1690, 1890, 1990 and 1895. They are 1/2″ thick and easily install in the spring assembly to increase the opener down-pressure by 75-90 lb.
They are required in the openers behind the tractor wheel tracks and/or air-cart wheel tracks, to increase the down pressure in these lower/compacted areas (relative to all other rows), to maintain a more consistent seeding depth.
Most drills and air-seeders require around 3 spring spacers per tire on 7.5″ spacing and around 2 per tire on 10″ spacing, but measure the width of the tires (relative to the row unit locations) to be sure.
See the YouTube video below. Look how much the 75-90 lb helps improve ride quality of the left 1890 row unit (with spring spacer added) to the right unit without the spring spacer. Note that everything else is set the same and the openers are on the same rockshaft. The openers are also adjusted the same to no-till wheat into cornstalks.