Bearing Press Drift

A bearing press is only as good as its drifts. The drift is the piece that touches the bearing face on every install stroke, and the difference between a bearing that goes in flush and one that goes in with a 0.1 mm dish across the outer race is whether the drift sits squarely on the outer race or rocks on a worn edge. The 1721.1 is the replacement-drift set for the Unior Bearing Press 1721 family, sized to match the bearing outside diameters Unior catalogs for current-generation hubs and bottom brackets.

What this set is for

Two common cases land a workshop on this product page:

1. A drift has been lost or worn out. The drifts in the original 1721 kit live in a fitted tray on the bench; once one rolls under a parts cabinet, the press is incomplete. The 1721.1 replaces individual drifts at the original spec.
2. A new bearing standard has arrived since the kit was sold. Hub and BB makers update bearing dimensions over time as axle standards shift and shells thin out. Older 1721 kits may not include every modern size; the 1721.1 brings the press back into coverage on current bearings.

How the drift works

Each drift sits between the press handle and the bearing face. The cup-shaped recess in the drift body engages the bearing's outer race (and only the outer race; the drift face is sized to clear the inner race and the bearing seal). Press load passes from the handle, through the drift, into the outer race, and into the shell. The bearing seats flush when the drift bottoms against the shell or against the press's protection plate.

Spec

• Material: premium flex plus carbon steel
• Face geometry: ground flat, sized to the bearing's outer-race face only
• Drive end: matches the 1721 press handle and shaft socket

Each drift is sized to a specific bearing OD; the set covers the catalog's modern hub and BB bearing range. For the seal-protection step on the final press stroke, the Bearing Drift Protection Plate 1721.2 sits between the drift and the bearing.

Compatibility

Drifts work with any 1721-family press body. The drift-to-handle interface is unchanged across the production history, so a 1721.1 set retrofits a kit that's been on the bench for years. The Over Axle Bearing Press Set extends drift coverage into shouldered-axle hub territory if your shop sees current DT Swiss, Industry Nine, or thru-axle hub designs.

Built in Zreče, Slovenia

Unior has been forging hand tools in Zreče since 1919, and is the official technical partner of multiple World Tour and downhill teams. These drifts are ground to the same dimensional tolerance as the originals; a replacement drift drops into an old kit without changing the press's working spec.

Pro tip from our mechanics

Drift wear shows up first as a crescent-shaped dent in the cup recess where one edge of the bearing OD has been carrying more load than the other. A drift that's wearing unevenly is a press that's installing bearings unevenly; replace the drift before you replace the bearings. For the bigger picture on which drift fits which bearing, see Bearing and headset service: a workshop guide →