ACL Race Series connecting rod bearings for Mini One / Cooper (W10B16)
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- Collection at our shopCartagena, Spain
ACL Race Series connecting rod bearings for Mini One / Cooper (W10B16) (part number 4B2903H), designed for engines that will operate under much higher loads and higher RPMs than stock.
The structure is trimetal, featuring a steel back, a copper-lead-tin lining, a nickel barrier, and a soft overlay that conforms and prevents seizing even under very high loads. In the connecting rod bearings, the overlay is thinner to better withstand fatigue.
ACL manufactures them with more "crush" (interference fit in the housing) than a standard bearing to ensure they stay firmly in place and dissipate heat better, and with more eccentricity, which helps maintain the oil film when the housing deforms at high RPMs.
In the standard size, ACL specifies them for a connecting rod journal of 43.992 to 44.008 mm, with a bearing width of 16.25 mm. For that diameter, they recommend an oil clearance of approximately 0.048 to 0.057 mm, measured with a micrometer and bore gauge. If the crankshaft has been reground, the measurement changes.
They do not have the silver-tin final plating of standard bearings, so their dark color—ranging from brown and black to bluish—is the factory finish and does not indicate any defect. ACL advises against polishing the bearing surface to adjust clearance; if more is needed, they are combined with the HX version, which provides an additional 0.025 mm of clearance.
If the crankshaft has been reground or you are unsure of the required size, please write to us with your engine code before ordering.