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 cocked is whether the drift face sits squarely on the bearing 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. Every size is machined to one bearing: drift and bearing slide onto the press spindle together, and as the handle tightens the drift face carries the press load, driving the bearing square into its seat. Keep the spindle straight while you tighten, and stop when you feel firm resistance; that resistance is the bearing reaching the bottom of its seat.

Spec

• Marking: every drift is engraved with its bearing designation and bore x OD size
• Sizing: each size is named for its bearing; the designation reads bore x outside diameter in millimeters (a 6901 drift is 12 x 24)
• Interface: a center bore that slides onto the threaded spindle of any 1721 or 1721BB press

Each drift is sized to a specific bearing; together the sizes cover the catalog's modern hub and BB bearing range. Unior's press sets also include a pair of plastic protectors, sold separately as the Bearing Drift Protection Plate 1721.2; these go on the far side of the hub or shell to protect painted and carbon surfaces while you press.

Compatibility

Drifts work with any 1721-family press body. Each size is sold as its own catalog part from the same 1721.1 series that ships in today's 1721 and 1721BB sets, so a lost or worn drift can be replaced without re-buying the kit. 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 sponsors professional road and mountain-bike race teams. Each drift is a catalogued Unior spare part and carries Unior's lifetime warranty.

Pro tip from our mechanics

Drift wear shows up first as marks or burrs on one side of the pressing face, where one edge of the bearing 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 →

FAQ

How do I know which drift size my bearing needs? Read the reference number on the bearing seal (a rear hub might run a 6901, for example) and pick the drift with the same designation. If the seal is unreadable, measure the bearing with calipers: every drift is named bore x outside diameter in millimeters, so a 12 mm x 24 mm bearing takes the 6901 12 x 24 drift.

Do these drifts fit my existing Unior bearing press? Yes. 1721.1 is the adapter series packed in the Universal Bearing Press 1721 and the Bottom Bracket Bearing Press Kit 1721BB. Every drift on this page slides onto the same threaded spindle those presses use, so a replacement or added size drops straight into either kit.

What does (2x) mean on some sizes? Those listings ship as a pair. The bottom bracket sizes (BB30 30 x 42, BB86/92 24 x 41, 22 x 41, and DUB 29 x 42) plus the R6 drift come as two matching pieces per pack; the standard cartridge bearing sizes come as one drift each. Unior's published pair weights run from 21 g for R6 to 203 g for DUB.

Do I need the 1721.2 protection plate as well? The plastic protectors are sold separately as the 1721.2. In the full press sets a pair backs the far side of the hub or shell so painted and carbon surfaces stay unmarked while you press; add them if your kit's protectors have gone missing or you are building a press setup from parts.