Bolt Hole Pattern refers to the specific arrangement and spacing of the mounting holes on a clutch flywheel, measured in mm. Your specific vehicle’s engine design determines which exact measurement you must match for a successful installation.
Which Bolt Hole Pattern suits your situation?
| If this is you | The Bolt Hole Pattern that suits you | Why |
|---|---|---|
| You are replacing a flywheel on a standard passenger car | The pattern specified by your vehicle’s manufacturer | Passenger vehicles use standardized layouts to ensure the flywheel aligns perfectly with the crankshaft flange. |
| You are working on a heavy-duty commercial truck | The high-torque specific pattern for your engine model | Commercial engines often use larger, more widely spaced patterns to distribute extreme torque loads across more bolts. |
| You are installing a performance upgrade on a sportbike | The racing-spec pattern for your specific displacement | Sportbike engines require precise alignment to maintain high-RPM stability and power delivery. |
| You are sourcing a part for a vintage or classic vehicle | The original equipment (OE) pattern from the production year | Older vehicles may use patterns that have since been phased out by modern manufacturing standards. |
Clutch Flywheels we have reviewed in detail
3 reviewed options, $159.13 to $409.99, with the full write-up behind each name.
LuK DMF117 Dual Mass Flywheel
Owners on a budget can find the best dual mass flywheel for heavy duty use under $500 in our comparison.
$159.13 price checked August 2026
Subaru Genuine Clutch Flywheel 12342AA090
$409.99 price checked August 2026
Read our full 12342AA090 Flywheel review
Make sure your component fits by learning how to choose your clutch flywheel spline count.
How do I find my correct Bolt Hole Pattern?
To find your Bolt Hole Pattern, you must identify the distance between the centers of the mounting holes on your current flywheel or the engine’s transmission bell housing.
You can establish this value by using a digital caliper or a high-precision tape measure to record the distance in mm between the center points of the bolts. For example, a pattern might be defined as a 100mm circle with a 75mm spacing between adjacent holes.
The Bolt Hole Pattern is often printed on the manufacturer’s technical specifications or the physical part itself. If the flywheel is already installed, you can consult the vehicle’s service manual or the official parts catalog using your Engine Identification Number (EIN) or Vehicle Identification Number (VIN).
Because even a 1mm discrepancy prevents the flywheel from sitting flush against the crankshaft, you should confirm the measurement twice before ordering. A qualified mechanic can verify these dimensions during a teardown to ensure the new component matches the existing mounting surface exactly.
What happens if the Bolt Hole Pattern is incorrect?
An incorrect Bolt Hole Pattern results in a component that physically cannot be mounted or, worse, sits at an incorrect angle on the crankshaft.
Identifying your vehicle’s specific needs is easier when you learn how to choose your clutch flywheel type.
Physical mounting failure
If the hole spacing is off by even a small margin, the bolts will not align with the threaded holes in the bell housing. This prevents the flywheel from being installed entirely, leading to a wasted order and a delay in repairs.
Drivetrain shudder and vibration
If a flywheel is forced onto a slightly different pattern or a mismatched flange, it may sit “cocked” or tilted. This misalignment causes severe harmonic vibration and drivetrain shudder as the clutch engages, which can lead to premature bearing wear and damage to the input shaft.
Heat dissipation and glazing
A flywheel that does not sit perfectly flat against the mounting surface creates uneven pressure across the friction surface. This leads to localized hot spots, rapid glazing of the clutch disc, and a significant reduction in the lifespan of the friction material.
What should I do if my measurement falls between two patterns?
If your measurement falls between two standard Bolt Hole Patterns, you must identify the specific engine model and manufacturer’s part number rather than choosing the closest numerical match.
In the automotive industry, a 1mm difference in a Bolt Hole Pattern usually indicates a different engine variant, a different manufacturing year, or a different transmission mating surface. You should never attempt to “force” a fit or use a pattern that is slightly larger or smaller than your measured value.
When in doubt, use the vehicle’s official part number to find the correct pattern. Ordering a part based on a “near-match” measurement often results in a component that is unusable. If the manufacturer’s documentation is unclear, have a qualified technician measure the bell housing’s mounting face to confirm the exact center-to-center distances before you place an order.