Which feature causes the curvature of the connecting rod bearings to be slightly greater than the curvature of the bearing bores?

Which feature causes the curvature of the connecting rod bearings to be slightly greater than the curvature of the bearing bores?

• A. Spread
• B. Clearance
• C. Parallax
• D. Taper

Answer: (A)

Spread is the outward deformation of a bearing shell when it’s clamped in place and loaded by the crankshaft. This slight bow makes the bearing’s inner surface more curved (smaller radius) than the bore it sits in. The bearing material flows a bit under cap torque and oil pressure, so the shell “spreads” and realizes a curvature greater than the bore’s. This helps achieve proper load distribution and oil film formation during operation. Other terms don’t describe this deformation process: clearance is simply the gap between journal and bearing, taper refers to a gradual change in thickness along the bearing, and parallax is a visual offset, not a mechanical change in curvature.

Spread is the outward deformation of a bearing shell when it’s clamped in place and loaded by the crankshaft. This slight bow makes the bearing’s inner surface more curved (smaller radius) than the bore it sits in. The bearing material flows a bit under cap torque and oil pressure, so the shell “spreads” and realizes a curvature greater than the bore’s. This helps achieve proper load distribution and oil film formation during operation.

Other terms don’t describe this deformation process: clearance is simply the gap between journal and bearing, taper refers to a gradual change in thickness along the bearing, and parallax is a visual offset, not a mechanical change in curvature.