S65 Rod Bearing and Bolt Replacement.

The e90/92 M3 is one of the most different evolution's in the history of BMW M3 history. Although a departure from the status quo of M vehicles we personally love the E90/92 M3 platform.

A customer of ours dropped his car off this past week for a preventative rod bearing swap on his ESS Supercharged E92 Coupe. This vehicle was tastefully modified with some Volk LE28n wheels and a mild exhaust giving it a nice sporty look and sound without being too wild for the street.





The rod bearings are responsible for keeping the rod end safe from the pounding it takes as 50-100 horsepower beats down on it from above. We use rod bearings made out of a softer metal than the crankshaft or the rod so that it breaks down first. The rod bearing doesn’t rest directly on the crank, instead it rides on an extremely thin layer of oil, that allows the crank to rotate freely and with extremely low resistance within the rod end. The issue with the S65 specifically is that the tolerance between the crankshaft and the rod is tight from the factory. When you increase power output or heat, the friction leads to the components growing in size and the oil getting thinner, which can lead to accelerated rod bearing wear on the upper half of the bearing shell. The bottom half of the bearing shell doesn’t usually see the same degree of wear as the upper as the forces applied to that half of the bearing is not anywhere near as strong as the ones during the power stroke.

ROD BEARINGS



ROD BEARING CLOSE UPS









After removing and inspecting each individual crankshaft journal with its respective rod and rod bearing for damage we proceed with installing the new components.





It is important to consider doing high strength rod bolts in any high RPM engine. Although the rod itself takes the brunt of the impact from the power stroke, when the engine is spinning at high rpms the piston wants to literally rip the rod off the crank, and the only thing holding it on is the rod bolts.

ARP is our go to supplier for engine fasteners. They have been making fantastic driveline and engine fasteners for years, and in addition to making great products they provide great customer service and will even create custom hardware if needed. Using a stronger rod bolt does a better job of keeping the crank end of the rod round. Whether or not it seems believable right now the shape of the crank end of the rod actually gets a bit oblong during parts of the engine cycle, and this can cause unnecessary stress and wear on the rod, the rod bearing, and especially the crank.

The BMW E92 S65 V8 M3 Engine is receiving a set of APR Custom Aged 625+ Rod Bolts during the course of its engine service.

What is the difference between ARP 625 and ARP 2000 bolts you ask?

The tried, true, and very popular ARP 2000 material is a quench and tempered heavily alloyed martensitic steel with a typical 44-47 C- scale Rockwell hardness and rated at 220,000 psi tensile strength. The ARP Custom age 625 + counterparts are comprised of a higher tensile strength super-alloy corrosion resistant material, also quench and temper heat treated, to a robust 260,000psi.





After the installation is successfully completed an oil change is performed to ensure the new rod bearings don’t see any debris. After proper oil level is ensured and the car is fully warmed up it is taken for a test drive to verify that the car is running as it should.





If all goes as planned another E92 M3 on it's way back home, this one just happens to be a little sweeter than your average!

If you have any questions or comments feel free to post or pm us for a direct response.