How to Choose a Flywheel for Your RSX or Civic Si Build
By PRL Motorsports - Premium Automotive Performance Products | Published: 2026-11-04
Category: 操作指南
Pick the right flywheel for your K20 RSX or Civic Si by matching weight to use, confirming clutch compatibility, and replacing the bearing.
Quick answer
For a street-driven RSX or Civic Si, choose a steel flywheel around 11–12 lb that matches your clutch kit and driving style; replace the flywheel bearing at the same time to avoid rework.
Why flywheel weight changes how the car feels
A lighter flywheel reduces rotational mass on the crankshaft, so the engine revs faster and delivers more power to the wheels. That can sharpen acceleration, but it also changes how the car behaves at low rpm. A very light flywheel can make standing starts easier to stall and may introduce more gear noise. For a mostly street-driven K20, a mid-weight steel flywheel is usually the better compromise than an ultra-light unit.
When a steel flywheel makes more sense than aluminum
Steel flywheels are generally more durable and less prone to warping than aluminum, and they work well with organic and street-performance clutch discs. If your RSX or Civic Si sees daily driving, autocross, or occasional track days, steel is the safer long-term choice. Aluminum flywheels can be lighter, but they often use a replaceable friction surface and may be noisier—so only go aluminum if you accept those trade-offs and verify clutch compatibility.
The bearing is not optional
The flywheel bearing (also called the pilot bearing) supports the transmission input shaft and is often overlooked during a clutch job. Reusing an old bearing can cause noise, vibration, or premature transmission wear. Since the transmission is already out, replacing it is cheap insurance. Confirm the bearing part number matches your engine and transmission before ordering.
Steps to choose and install the right flywheel
- Confirm your engine and transmission: Identify your exact engine code (e.g., K20A2, K20Z1, K20Z3) and transmission type. Flywheel fitment depends on both, so check the product description or call the manufacturer before ordering. Common mistake: assuming all K20 flywheels are interchangeable. Write down your engine code and transmission code before you shop.
- Match flywheel weight to your driving: For a street car that sees occasional spirited driving, choose a steel flywheel in the 11–13 lb range. If you mostly race and can tolerate stalling and noise, a lighter unit may be acceptable. Checkpoint: be honest about how often you sit in traffic. Lighter is not always better for a daily driver.
- Verify clutch compatibility: Flywheel and clutch must be designed to work together. Many aftermarket flywheels specify compatibility with certain clutch stages or disc types. Confirm your clutch kit matches the flywheel before purchase. Mistake: buying a flywheel that only works with a specific clutch you do not have. Check the clutch kit’s recommended flywheel or vice versa.
- Replace the flywheel bearing: Order a new pilot/flywheel bearing with your flywheel. For 2017–2021 Civic Type-R and 2018+ Accord 2.0T manual, the Genuine Honda 91006-RK2-003 is a direct fit. For RSX or Civic Si, look up the correct OEM part number for your model. Mistake: reusing the old bearing because it “looks fine.” A new bearing is inexpensive insurance against future noise.
- Inspect and prepare the crankshaft flange: Clean the crankshaft flange and check for burrs or corrosion before installing the flywheel. Use a straightedge to check flatness if you suspect issues. Mistake: installing a flywheel on a dirty or damaged flange, which can cause runout and vibration. A clean, flat mating surface prevents vibration.
- Torque fasteners correctly: Use new flywheel bolts if specified, and torque them in a star pattern to the factory spec with a calibrated torque wrench. Apply thread locker only if the service manual calls for it. Mistake: guessing torque or reusing stretch bolts. Always follow the factory torque sequence and spec.
Product facts
- Comp Clutch 2002-2008 RSX / 2002-2009 Civic Si 11.5lb Steel Flywheel: Competition Clutch ST lightweight steel flywheel weighs 11.5 lb and is designed for street/strip use with Stage 1 and Stage 2 clutch kits. This weight is a practical middle ground for a K20 that sees street driving and occasional track time, and it pairs with common upgraded clutches.
Comp Clutch 2002-2008 RSX / 2002-2009 Civic Si 11.5lb Steel Flywheel - Genuine Honda 2.0T Civic Type-R / Accord Flywheel Bearing 91006-RK2-003: Genuine Honda flywheel bearing 91006-RK2-003 fits 2017–2021 Civic Type-R FK8 and 2018+ Accord 2.0T manual models. If you drive one of these models, this is the correct OEM bearing to replace during a clutch or flywheel job; for older RSX or Civic Si, verify your own part number.
Genuine Honda 2.0T Civic Type-R / Accord Flywheel Bearing 91006-RK2-003
