Checking bearing clearances with a plastic gauge

KS | Kolbenschmidt | Motorservice

How do I easily check the bearing clearance on the crankshaft and connecting rod? What is the maximum permitted bearing clearance? And what is the minimum bearing clearance? How are measuring strips used? When are oversize engine bearings used? This video makes everything clear.

A plastic gauge is a thin calibrated plastic strip. It can be used to check bearing clearance and also gap dimensions. It is used at points on connecting rod or crank bearings where a quick measurement with a micrometer is not possible. 

Once the bearing cap has been removed, clean the surface of the shaft and the bearing shell. A suitable plastic gauge strip is now attached at a right angle to the sliding surface of the shaft with a small amount of grease. To prevent the measuring strip adhering to the bearing surface, a small amount of silicone spray can be applied to the bearing surface. The bearing cap is then fitted as specified.

Attention: Do not turn the crankshaft while doing this as otherwise the filament will smear and distort the measuring result. 


To perform the measurement, remove the bearing cap again and use the measuring scale provided to check how far apart the measuring strips have been pressed. The further apart the measuring strips have been pressed, the smaller the bearing clearance. This value can then be compared with the catalogue data or the specifications in the repair shop manual.

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Measure bearing clearances with the Kolbenschmidt Plastic Gauge

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