I have a 35 year old Trek Mountain bike that I have refurbished. - Rear wheel is true within +/-5 thousandth (it is true as mounted on the bike using a calipers clamped to the frame and perpendicular to the rim) - Bearings (9 x 1/4") have been replaced and cone is tight (no perceptible rocking) - All spokes are intact - The wheel is set all the way back in the frame slot
When I spin the wheel under no load, as expected, it spins true without any perceptible wobble.
BUT when I ride, I feel and hear it rubbing back-and forth on the brakes -- and when I look down, I can see the wheel (and the rim itself) very clearly wobbling back and forth between the caliper pads.
Also, if I put lateral pressure on the rim with my fingers, I can feel it giving laterally, though this may be normal given that it is all under tension anyway.
Note bike was working fine until last week.
What could be causing a wobble under load that doesn't exist under no-load?
Could it be that the spokes aren't under enough tension? (i.e. would it be helpful to say tighten each spoke by say 1/2 turn?)