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5.0L 40v - S85B50
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5.0L 40v - S85B50
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Set of 10 forged 4340 steel connecting rods for BMW M5 E60 / M6 E63 V10 5.0L 40V S85B50.
The BMW S85B50 is the 5.0-litre naturally aspirated V10 (4,999 cc, 92 mm bore, 75.2 mm stroke) with 40 valves, directly inspired by BMW's Formula 1 experience. It powers the M5 (E60/E61) and M6 (E63/E64), producing 507 hp at 7,750 rpm and 520 Nm, with an 8,250 rpm redline, an exceptional engine with a racing temperament.
Built from 2004 to 2010, this V10, unique within BMW, is as demanding as it is fascinating. Its factory rods, stressed by very high rpm, are a known weak point on pushed or high-mileage examples. These forged connecting rods make the bottom end reliable for the long term on a V10 that has become rare and precious.
Machined from forged 4340 steel, these rods replace the factory parts whose strength fades at very high rpm. Forging aligns the metal grain with the loads, giving far greater fatigue resistance than a sintered rod, a decisive asset on a ten-cylinder that spins past 8,000 rpm.
Each rod is shot-peened, inspected and weight-matched to ±1 g across all ten in the set, essential for balancing a V10. The supplied ARP hardware locks the assembly together and safely allows a build, a raised limiter and sustained track use.
| Reference | Brand | Profile | Bolts | Pin diameter OEM 21 mm | Small-end width | Big-end diameter OEM 56 mm | Big-end width | Center-to-center OEM 140.7 mm | Weight per rod |
|---|---|---|---|---|---|---|---|---|---|
| R-BMW-015-I | ZRP | I | ARP 2000-3/8"-38mm | 21 | 56 | 18.5 | 140.7 | 499 | |
| R-BMW-015-I-L19 | ZRP | I | ARP L19-3/8"-38mm | 21 | 56 | 18.5 | 140.7 | 499 |
| Rod | Bolts | Torque | Recommended stretch |
|---|---|---|---|
| ZRP (R-BMW-015-I) | ARP 2000 | 61 N·m | 0.140 – 0.152 mm |
| ZRP (R-BMW-015-I-L19) | ARP L19 | 67.8 N·m | 0.152 – 0.165 mm |
Manufacturers recommend the stretch-gauge method as the reference: the instructions supplied with the kit always take precedence. The torque figures correspond to assembly with ARP lubricant.
| 4340 steel, a nickel-chromium-molybdenum alloy, combines high mechanical strength with good ductility. Against the factory sintered metal, it offers about +19% yield strength, +8% tensile strength and +19 to +37% fatigue resistance. On an engine that lives at very high rpm, this means a rod that is markedly more durable and stable under load. |
 | I-Beam profile. Its slimmer central section reduces moving mass, a decisive asset on a V10 that revs as high as the S85B50, while keeping rigidity suited to intensive use. |
The rod bolt is the most heavily loaded part of the assembly: it keeps the cap closed on every cycle, at very high rpm. This kit is fitted with ARP 2000 / L19 hardware.
 | ARP 2000: the high-performance benchmark, with no storage constraints. Handles up to 200 hp per cylinder in 3/8" and 8,500 rpm. Ideal for circuit, trackday, drift, rally, drag and hillclimb, strength, reliability and versatility combined. |
 | L19 (tensile strength ~260,000 psi, i.e. ~1,793 MPa) is designed for engines pushed to the extreme, up to 200 hp per cylinder with 5/16" bolts or 250 hp per cylinder with 3/8" bolts, and up to 10,000 rpm: very high boost pressure, sustained high rpm and high cylinder pressure. It is the choice for big-power builds: drag racing, drift, rally and circuit use. Caution: sensitive to corrosion and hydrogen embrittlement, it must always be stored and fitted oiled, away from moisture. |
| In addition to torque tightening, measuring bolt stretch with a dial indicator remains the most reliable way to guarantee preload. The instructions supplied with the kit always take precedence. |
 | ZRP, a Greek specialist in high-performance forged connecting rods, machines its parts from 4340 steel and weight-matches them. For the S85B50, the range comes in I-Beam profile with ARP 2000 / L19 hardware. |
 | 1) Small end 2) Small-end diameter 3) Rod beam 4) Rod bolt 5) Big end 6) Rod nut / bolt 7) Rod cap 8) Big-end diameter 9) Center-to-center |
These forged connecting rods are compatible with the factory BMW S85B50 engine and its builds. Vehicles concerned:
| Brand | Model (chassis) | Engine code | Power | Years |
|---|---|---|---|---|
| BMW | M5 (E60/E61) | S85B50 | 507 hp | 2004–2010 |
| BMW | M6 (E63/E64) | S85B50 | 507 hp | 2005–2010 |
OEM reference: 11 24 7 838 623 (rod set).
On an S85B50, a rod failure at high rpm, a dreaded event on this V10, results in a very heavy bill: a rare block, highly specialised labour, long downtime.
For a controlled budget, making the rotating assembly reliable with a forged set from the start of the build prevents failure and preserves an irreplaceable engine. An investment far cheaper than a rebuild.
For the same budget: more reliability, a comfortable rpm margin and the peace of mind of a bottom end built to last. The most rational way to preserve one of BMW M's most iconic engines.
