Notchy steering or play in the headset usually points to a worn bearing, and the lower bearing takes the brunt of the abuse. Road vibration, washing the bike, and general riding all work against the seals over time. This FSA lower headset bearing fits the 1-1/2" lower position on most Cervelo frames from 2016 forward, covering the R5, Soloist, Caledonia, Caledonia-5, Aspero, Aspero-5, R5CX, P-Series, and C-Series models. The sealed cartridge design presses directly into the frame's lower head tube cup.

The bearing uses 36° x 45° angular contact geometry, which is the standard FSA spec for tapered steerer forks. That angle combination handles both radial loads from the rider's weight and thrust loads from braking and cornering forces. The cartridge measures 40mm inner diameter by 51.8mm outer diameter by 7.5mm width, matching the integrated headset cups pressed into Cervelo's lower head tubes. On the ZHT-5 and ZFS-5 mountain frames, this same bearing works in both the upper and lower positions since those bikes run a straight 1-1/2" steerer rather than tapered.

Replacing a headset bearing is straightforward if you have the right press tools. The old bearing drifts out from the opposite side, and the new one presses in flush with the cup. A thin layer of grease on the bearing's outer race helps with installation and provides some corrosion protection. If the headset feels rough after installing new bearings, check that the crown race is seated properly and that the preload adjustment isn't overtightened.