The Timken Company
The Timken Company
4500 Mt Pleasant St. NW
N. Canton, OH 44720
Phone: (234) 262-3000
E-Mail: CustomerCAD@timken.com • Web site: www.timken.com
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This is the most basic and most widely used type of tapered roller bearing. It consists of two main separable parts: the cone (inner ring) assembly and the cup (outer ring). It is typically mounted in opposing pairs on a shaft.
Unit of Measure

Key Dimensions

Series

 N/A 78000C

Cone Part Number

 N/A 78250AC

Bore (d)

 N/A 2.5 in63.5 mm
Dynamic Radial Load Rating - 90M Revs (C90) 1 N/A 13800 lbf61300 N
Dynamic Radial Load Rating - 1M Revs (C1) 2 N/A 53200 lbf237000 N
C1 - Dynamic Radial Rating (Two-Row, 1 million revolutions)3 N/A 92600 lbf412000 N
Dynamic Radial Load Rating 2-Row - 90M Revs (C90-2row) 4 N/A 24000 lbf107000 N
K Factor 5 N/A 0.67

Other Dimensions

Inner Ring Width (B)

 N/A 1.3085 in33.236 mm
Max Shaft Fillet Radius6 N/A 0.2 in5.1 mm

Shaft Backing Shoulder Diameter - Frontface (da)

 N/A 3.05 in77.5 mm

Shaft Backing Shoulder Diameter - Backface (db)

 N/A 3.66 in93 mm

Cage Location Relative to Frontface (Ab) 

 N/A 0.21 in5.3 mm

Cage Location Relative to Backface (Aa)

 N/A 0.22 in5.6 mm
Effective Center Location7 N/A 0.33 in8.4 mm

Weight

 N/A 11.25 lb5.102 Kg

Ratings

Static Radial Load Rating (C0)

 N/A 52600 lbf234000 N
Ca90 - Dynamic Thrust Rating (90 million revolutions)8 N/A 20400 lbf90900 N

Factors

G1 Factor

 N/A 71.3

G2 Factor

 N/A 17.6
Geometry Factor (Cg)9 N/A 0.0926
  • 1 Based on 90 x 106 revolutions L10 life, for The Timken Company life calculation method. C90 and Ca90 are radial and thrust values.
  • 2 Based on 1 x 106 revolutions L10 life, for the ISO life calculation method.
  • 3 Based on 1 x 106 revolutions L10 life, for the ISO life calculation method.
  • 4 Based on 90 x 106 revolutions L10 life, for The Timken Company life calculation method. C90 and Ca90 are radial and thrust values for a single-row, C90(2) is the two-row radial value.
  • 5 These factors apply for both inch and metric calculations. Consult your Timken representative for instruction on use.
  • 6 These maximum fillet radii will be cleared by the bearing corners.
  • 7 Negative value indicates effective center inside cone backface.
  • 8 Based on 90 x 106 revolutions L10 life, for The Timken Company life calculation method. C90 and Ca90 are radial and thrust values for a single-row, C90(2) is the two-row radial value.
  • 9 Geometry constant for Lubrication Life Adjustment Factor a3l.