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2.5L 24v - M50B25TU (with VANOS)
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2.5L 24v - M50B25TU (with VANOS)
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Set of 6 forged 4340-steel connecting rods for BMW 2.5L 24V M50B25 / M52B25 (single VANOS).
Launched in 1990, the 2.5L M50B25 straight-six introduced BMW's DOHC 24-valve engine generation: double overhead camshafts, four valves per cylinder and a forged crankshaft. With a displacement of 2,494 cc (84 mm bore, 75 mm stroke), it produces 192 hp. From 1992, BMW added intake variable valve timing (the so-called 'single VANOS' configuration), which improves low-end torque and flexibility without changing the bottom-end architecture.
In 1995, the M52B25 took over with a lighter block and kept single VANOS, for 170 hp in the 323i and 523i. On these engines pushed in tuning, torque and cylinder pressure climb well beyond the original figures: it is the rotating assembly, and first of all the connecting rods, that becomes the critical point to reinforce.
A forged connecting rod is shaped by hot die-forging the steel: the material is compressed and its grain follows the part's geometry, giving it far greater strength and endurance than a production sintered-metal rod. Machined and balanced, it withstands the high cylinder pressures, high rpm and torque peaks of tuned engines. It's the assurance of a bottom end that lasts when the original power is exceeded.
| Reference | Brand | Profile | Hardware | Pin diameter OEM 22 mm | Small-end width | Big-end diameter OEM 48 mm | Big-end width | Center-to-center OEM 140 mm | Weight per rod |
|---|---|---|---|---|---|---|---|---|---|
| R-BMW-002-I | ZRP | I | ARP 2000-3/8"-38mm | 22 mm | 48 mm | 21.9 mm | 140 mm | 498 g | |
| R-BMW-002-I-L19 | ZRP | I | ARP L19-3/8"-38mm | 22 mm | 48 mm | 21.9 mm | 140 mm | 498 g |
| Rod | Hardware | Tightening torque | Recommended stretch |
|---|---|---|---|
| ZRP (R-BMW-002-I) | ARP 2000 | 61 N·m | 0.140 – 0.152 mm |
| ZRP (R-BMW-002-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 prevail. The torque figures correspond to assembly with ARP lubricant.
| All these ZRP rods are forged from 4340 nickel-chromium-molybdenum alloy steel, the motorsport standard. Compared with the original sintered metal, it offers roughly 19% higher yield strength, around 8% more tensile strength and 19 to 37% better fatigue endurance. This mechanical margin is exactly what's needed to handle forced induction, high rpm and the high torque of a build. |
 | I-Beam profile. It's the profile chosen here. Light and rigid, it limits reciprocating mass and suits tuned M50 and M52 straight-sixes perfectly, where high-rpm response is sought without adding weight to the rotating assembly. |
 | ARP 2000. Versatile high-performance bolt with no storage constraints. In 3/8" diameter, it covers up to around 200 hp per cylinder and 8,500 rpm: more than enough to reinforce an M50 or M52 2.5L on track, trackday, drift, rally, drag or hillclimb. |
 | ARP L19. Designed for engines pushed to the extreme, when cylinder pressure and sustained rpm exceed the ARP 2000's range. In 3/8", it targets around 250 hp per cylinder and 10,000 rpm, for big-power builds in drag, drift, rally and track. Sensitive to corrosion and hydrogen embrittlement, it must be stored and fitted oiled. |
| On high-performance bolts, the reference tightening is done by checking stretch with a gauge (stretch gauge), more precise than torque alone: you measure the actual elongation of the fitted bolt. Always follow the values in the instructions supplied with the kit. |
 | ZRP, a Greek brand of high-performance forged connecting rods, designed by Alex Drakos in Athens. Each rod is forged from 4340 steel, precision-machined and balanced to ±1 g to stay reliable at high rpm. Available in I-beam or H-beam profile with ARP 2000, L19 or Custom Age 625+ bolts, they are designed and inspected in Greece, and proven in rally, on circuit and in drift. |
 | 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 |
| Brand | Model (chassis) | Engine code | Power | Years |
|---|---|---|---|---|
| BMW | 325i / 325is (E36) | M50B25 | 192 hp | 1990–1995 |
| BMW | 325i Cabriolet (E36) | M50B25 | 192 hp | 1993–1995 |
| BMW | 525i / 525iX (E34) | M50B25 | 192 hp | 1990–1995 |
| BMW | 525i / 525iX Touring (E34) | M50B25 | 192 hp | 1991–1996 |
| BMW | 323i (E36) | M52B25 | 170 hp | 1995–1999 |
| BMW | 323ti Compact (E36) | M52B25 | 163–170 hp | 1997–2000 |
| BMW | 323i Coupé / Cabriolet (E36) | M52B25 | 170 hp | 1995–1999 |
| BMW | 323i Touring (E36) | M52B25 | 170 hp | 1995–1999 |
| BMW | 523i / 523i Touring (E39) | M52B25 | 170 hp | 1995–2000 |
OEM reference: M50B25 11 24 1 730 420; M52B25 11 24 1 739 725 (replaced by 11 24 1 437 211).
On a tuned M50 or M52, a failing production rod often takes the block and crankshaft with it: the bill then far exceeds the price of a set of forged rods. Investing at build time in ZRP 4340-steel rods and ARP hardware secures the bottom end for the long term and saves a full rebuild. A complete kit, designed for the displacement, remains the most cost-effective spend for driving with confidence.
