Porsche Rod Bearings

Worried about your Porsche’s engine reliability due to spirited driving or track events? For your Porsche Rod Bearing needs, contact Bavarian Rennsport.

What is an IMS Bearing (Rod Bearing)?

A Rod Bearing is made up of two halves of smooth metal that wraps around the crankshaft. This design allows a very thin film of oil to be continuously pumped in between the pieces of metal to provide lubrication. The job of a Rod Bearing is to act as a fail-safe because the softer metal typically wears down and fails before the crankshaft or the rod itself. Both of those repairs are far more extensive and time-consuming if damaged from not replacing your rod bearings.

In most Porsche engines, the main bearings are supplied oil from the main oil galley running parallel to the crankshaft within the engine case, on the 4/5/6 side of the case. This lubricating oil is then pushed into the small clearance between the bearings and crankshaft through holes in the bearing shells. The oil film is not created by the pressure pushing the oil, but by the rotational force of the crankshaft. The oil is then pulled into the cavity and the crankshaft is “raised” off the main bearings by this thin layer of lubricating oil. It is recommended to replace Porsche Rod bearings around 80-90K miles depending on the owners driving habits and service/maintenance routine.

High-Performance Engines

If your Porsche engine produces more than 500-600 HP, a coated high-performance type rod bearing is required. Main bearings are not typically available in high-performance variants and Connecting rods are subject to extremely high loads. The highest loads are the inertia loadings when the rod is at TDC on the exhaust stroke. This is when the weight of the piston, pin, rings, clips and the small end of the rod all combine and try to pull collective masses out through the top of the engine. It puts extreme loads on the rod cap, bolts and tries to stretch the rods themselves. This stretching elongates the vertical dimension of the rod’s big end and narrows the width of the bearing across the rod parting line.
As this dimension shrinks, so does the clearance and the oil film. For this reason, high-performance bearings are thinner at the parting line to counteract this narrowing effect called “bearing eccentricity”.

Bavarian Rennsport recommends always upgrading to performance or aftermarket style bearing to help decrease the chances of suffering a catastrophic engine malfunction from a spun rod. Bi-metal rod bearings are recommended for those enthusiasts trying to get the most out of their car while also making sure they keep their engine happy. Tri-metal bearings are the next step up from Bi-metal as they are designed for higher-performance levels and typically used in race applications.
They have 3 layers and usually have a hardened steel back with tin or copper-lead underlay, and an overlay of babbit. These tri-layered rod bearings are designed to slightly deform under pressure allowing the bearing to “touch” the crankshaft journal under extreme pressure without friction or heat welding itself to the journal.

Book A Porsche Service Appointment

Call or Text (904) 270-9390

Send Your Symptoms