I changed my rollers on my SP15 because I found that one side of my press was printing lighter than the other side (my rollers were about 10 years old) but I’m finding that I’m having the same problem with the new rollers. The rollers are set at the right height from left to right with the new rollers?
Here’s a photo of the drum balance screws.
Bearings are certainly a possibility, but there are a few other possible causes:
• Roller core collar set too close to the bearing block could inhibit the adjusting post from seating properly in the hole in the side plates.
• Drum may be unbalanced. Place a spirit level on the bed then compare with the drum. Check the condition of the springs (X-20771, manual sheet 282-A). If they are fine, then adjust the balance screws (F-816, manual sheet 247). Turning the screw to the right pushes the drum down.
• Brass journal ends on the small steel rider that contacts the front roller could be bent.
There was a post on briarpress about a challenge 15mp with a similar problem. see http://briarpress.org/40652
it was the impression bearing that needed adjusting – sounds like your problem