MartO,
I had exactly the same sound on my Plus Four 2025 immediately after its 1000 mile service, where they fixed the axle clonk (I think by greasing splines and tightening spinners) and the Nitron squeak - at all four corners. I erroneously thought the sound was e.g. a heavy tool accidentally left somewhere under a seat or under spare etc, being temporarily airborne over bumps. Nothing to be found. The heavy thump sound over bumps disappeared after about 100 miles and then the axle clonk returned after about 300.... The Nitrons remain squeak-free, after a further 2000 miles.
Guy
