Sitta GP Aluminium Rear Sprocket for BMW HP4, HP4 Race & S1000RR HP Forged Wheel – 204Y-HR20GP, 37–47 Teeth, 520 Pitch

When only the finest materials will do, the Sitta GP Aluminium Rear Sprocket 204Y-HR20GP delivers a measurable step up in build integrity for BMW HP4, HP4 Race, and S1000RR owners running the HP forged wheel. Machined from high-grade aluminium and treated with Sitta's proprietary SuperHard coating, this sprocket combines an ultralight construction — just 320 g at 45 teeth — with exceptional surface hardness that stands up to the relentless demands of track day and road riding alike.

Key Features

• SuperHard-coated aluminium construction: the advanced surface treatment significantly extends service life compared to standard anodised sprockets, resisting wear even under sustained high-load conditions.
• Ultralight at just 320 g (45-tooth version), reducing unsprung mass and sharpening throttle response without compromising structural integrity.
• CNC-machined to exacting tolerances for a precise, vibration-free power transfer and a perfect fit to the 70/100 mm, 5-bolt sprocket carrier.
• 520 pitch specification, optimised for high-performance race and sport-road use on compatible chain kits.
• Available in 37 to 47 teeth, giving you the flexibility to tailor your final gearing precisely to your circuit layout or riding style.
• Exclusive Black SuperHard finish — a purposeful, understated aesthetic that signals serious intent.

Build Quality & Materials

The HR20GP designation marks a revised, second-generation design from Sitta. The SuperHard coating is not merely cosmetic: it creates a significantly harder wear surface on each tooth profile, reducing the rate at which the sprocket beds into the chain under acceleration loads. The result is a longer service interval and more consistent gearing feel across the life of the component. The CNC milling process ensures that every tooth form and bolt hole is held to tight tolerances, so fitment to the BMW HP forged wheel carrier is clean and repeatable — no shimming, no compromise.

Choosing Your Gearing

The wide tooth range available on the 204Y-HR20GP makes it straightforward to dial in exactly the gearing ratio your riding demands.

• Fewer teeth (37–42): reduces final drive ratio, raising top speed and lowering engine rpm at cruising speeds — ideal for long, fast circuits or motorway touring.
• More teeth (43–47): increases final drive ratio, sharpening acceleration and improving low-speed agility — the preferred choice for tight, technical tracks or spirited road riding.

Run the 204Y-HR20GP against your standard gearing data and choose the tooth count that puts your BMW's power band exactly where you need it.

Fitment & Compatibility

This sprocket is designed exclusively for BMW models equipped with the HP forged wheel and the 70/100 mm, 5-bolt sprocket carrier. Compatible fitments are listed below:

• BMW HP4
• BMW HP4 Race
• BMW S1000RR with HP Schmiederad (HP forged wheel)

Chain pitch: 520 only. Verify your chain specification before ordering. Part number: 204Y-HR20GP.

Specifications