From a press release:

Triumph Motorcycles – Recall

Our in-service monitoring program has identified that on some of the single sided swingarm models below, the rear wheel roller bearing may seize resulting in an inability to control the stability of the motorcycle. This information has been forwarded to our dealer network via Service Bulletin 313. Consumers should check their Service/Warranty handbook which accompanies the Owners Manual, a note should have been entered by the selling dealer upon completion of this NHTSA Recall Campaign. If there is no note, please contact your dealer to verify this repair has been completed or make an appointment to have the machine inspected / updated.

Models included are:
Centennial Daytona, Sprint ST and Speed Triple

Affected VIN (frame numbers, last 6 digits) are: 132693 through 161257