Vortex Racing Steel Rear Sprocket 520 45 Tooth- Black - 251AS-45

• 520 Chain Pitch
• 45 Teeth

The Vortex Racing Steel Rear Sprocket 520 45 Tooth – Black (251AS-45) is a precision-built replacement/upgrade sprocket for riders running a 520 chain pitch drivetrain. Manufactured from steel to Vortex's tight tolerances, this 45-tooth sprocket is designed for concentric, true running on the wheel hub while keeping rotating mass in check—an easy way to dial in acceleration and throttle response without sacrificing durability.

Key Features & Benefits

• Steel construction — built to precise specifications for concentricity and long-term durability under repeated hard acceleration and braking loads.
• Lightening holes — machined into the sprocket body to reduce rotating (unsprung) mass compared to a solid design, helping the drivetrain spin up quicker.
• 520 chain pitch — matches OEM or converted 520 chain setups, a common choice for riders chasing lighter overall drivetrain weight.
• 45-tooth count — a mid-range gearing option; per Vortex's own sprocket buying guide, changing rear tooth count is the easiest way to fine-tune final drive ratio (roughly 2–3 rear teeth for every 1 tooth changed up front).
• Black finish — wears well and blends cleanly with black wheels, chains, and drivetrain hardware.

Specifications

• Brand: Vortex Racing
• Material: Steel
• Chain Pitch: 520
• Tooth Count: 45
• Finish: Black
• MPN: 251AS-45
• SKU: VTX251AS-45

Fitment

This sprocket is part of Vortex's 251A rear sprocket family and is built to bolt to the corresponding 251A carrier bolt pattern used on a range of chain-drive motorcycles running a 520 pitch chain. Exact make/model application depends on your bike's OEM bolt pattern and hub, so we recommend confirming compatibility using the fitment checker on this product's ThreePiece.us page or reaching out to our team with your bike's year, make, and model before ordering. If your bike uses a 525 or 530 chain, Vortex also offers this same 45-tooth sprocket in the 528AS-45 and 526AS-45 versions, and 44-tooth and 41-tooth options are available in the 520 pitch (251AS-44, 251AS-41) if you need a different final drive ratio.

Why Buy from ThreePiece.us

ThreePiece.us backs this Vortex Racing sprocket with free shipping and 0% APR financing through Affirm, so you can get your drivetrain dialed in without paying it all up front. Our fitment specialists are on hand to help you match the correct tooth count, chain pitch, and bolt pattern to your specific bike before you order, reducing the risk of returns or downtime.

Frequently Asked Questions

What chain pitch does the 251AS-45 use?
It's built for a 520 chain pitch. If your bike runs 525 or 530 chain, Vortex offers the same 45-tooth sprocket as the 528AS-45 or 526AS-45.

What is this sprocket made from?
It's manufactured from steel for durability and concentric running, with lightening holes machined in to reduce rotating mass versus a solid sprocket.

Can I get a different tooth count for different gearing?
Yes. Vortex also offers 44-tooth (251AS-44) and 41-tooth (251AS-41) versions in the same 520 pitch black steel design if you want to change your final drive ratio.

Does ThreePiece.us offer financing and free shipping on this part?
Yes, this sprocket ships free and can be purchased with Affirm financing at checkout.