Why does the OEM N55 and S55 crank hub fail, and how does the BMW N55 S55 crank hub upgrade fix it?

The factory crank hub is a three-piece design that relies on friction between plates to hold correct timing alignment. Over time or under load, that friction can be overcome, letting the hub slip rotationally on the crankshaft and pull timing out of alignment, which can cause catastrophic engine damage with no warning. The BMW N55 S55 crank hub upgrade replaces the three-piece assembly with a single-piece billet EN36 steel hub, permanently eliminating that slippage risk.

Is this unpinned BMW N55 S55 crank hub strong enough for my build, or do I need the 4-pin version?

This unpinned one-piece hub is the correct choice for stock and lightly modified N55 or S55 engines, eliminating the OEM failure mode without the added dowel-pin mechanical lock. For builds over 700hp or any application demanding absolute certainty against slip, MMX recommends the 4-pin pinned variant of this hub, which adds four aerospace-machined dowel pins for additional security.

What is included with the BMW N55 S55 crank hub upgrade?

The kit includes the billet EN36 steel single-piece hub and a new OE-spec crank bolt for proper high-torque installation. The optional MMX Capture Plate, which secures the crank bolt against loosening from engine harmonics, is sold separately.

Do I need the Capture Plate as well?

The Capture Plate addresses a separate failure mode from the crank hub itself. The BMW N55 S55 crank hub upgrade prevents hub-to-crank rotational slip; the Capture Plate prevents the crank bolt from gradually backing out due to engine harmonics. The two are complementary, and pairing both provides the most complete protection, though the hub alone resolves the primary slippage risk.

Can this be installed with the engine in the car?

Yes. The BMW N55 S55 crank hub upgrade can be installed with the engine in situ, though access to the front of the engine is required and typically involves removing the front bumper or radiator depending on the specific model. Professional installation is recommended given the precision required.

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Description

MMX Billet One-Piece Crank Hub Upgrade for BMW N55 and S55 Engines

BMW N55 S55 crank hub upgrade from MMX Performance is a critical reliability enhancement that addresses the well-known failure risk of the factory three-piece crank hub. The factory design relies on friction between plates to maintain timing, and under sustained load or simply over time, that friction can be overcome, allowing the hub to slip rotationally on the crankshaft and pull crank-to-cam timing out of alignment the leading cause of catastrophic N55 and S55 engine damage with no warning beforehand. The MMX BMW N55 S55 crank hub eliminates this with a single-piece design machined from EN36 billet steel and case-hardened to a depth of 0.75mm, permanently solving the slippage issue that the OEM friction-based three-piece assembly is prone to. A new crank bolt is included for proper high-torque installation. This unpinned one-piece hub is the correct upgrade for stock and lightly modified engines, delivering precise, consistent timing whether the engine remains factory-tuned or has received moderate power increases. For builds over 700hp or any application demanding absolute certainty against slip, MMX also offers a 4-pin pinned variant of this hub, and an optional capture plate is available separately to lock the crank bolt against loosening from engine harmonics.

Features

One-piece billet EN36 steel construction with 0.75mm case hardening
Permanently eliminates OEM three-piece crank hub slippage
Precise, consistent timing even under increased power or load
Suitable for both factory-tuned and lightly modified engines
Includes new crank bolt for proper high-torque installation
Compatible with N55 and S55 engines
Optional MMX Capture Plate available to secure crank bolt against harmonic loosening

Applications

BMW 135i: E82, E88 | 2010-2013
BMW 335i: E90, E91, E92, E93, F30, F31, F34 | 2010-2015
BMW 435i: F32, F33, F36 | 2013-2016
BMW 535i: F07, F10, F11 | 2010-2017
BMW 640i: F06, F12, F13 | 2011-2018
BMW 740i: F01, F02 | 2012-2015
BMW M135i: F20, F21 | 2012-2016
BMW M2: F87 | 2016-2018
BMW M2 Competition: F87 | 2018-2021
BMW M235i: F22, F23 | 2014-2016
BMW M3: F80 | 2014-2018
BMW M4: F82, F83 | 2014-2020
BMW X3 xDrive35i: F25 | 2011-2017
BMW X4 xDrive35i: F26 | 2014-2018
BMW X5 sDrive35i: F15 | 2014-2018
BMW X5 xDrive35i: F15 | 2014-2018
BMW X6 sDrive35i: F16 | 2015-2019
BMW X6 xDrive35i: F16 | 2015-2019

Notes

Only compatible with N55 and S55 engines

Frequently Asked Questions

Why does the OEM N55 and S55 crank hub fail, and how does the BMW N55 S55 crank hub upgrade fix it? The factory crank hub is a three-piece design that relies on friction between plates to hold correct timing alignment. Over time or under load, that friction can be overcome, letting the hub slip rotationally on the crankshaft and pull timing out of alignment, which can cause catastrophic engine damage with no warning. The BMW N55 S55 crank hub upgrade replaces the three-piece assembly with a single-piece billet EN36 steel hub, permanently eliminating that slippage risk.
Is this unpinned BMW N55 S55 crank hub strong enough for my build, or do I need the 4-pin version? This unpinned one-piece hub is the correct choice for stock and lightly modified N55 or S55 engines, eliminating the OEM failure mode without the added dowel-pin mechanical lock. For builds over 700hp or any application demanding absolute certainty against slip, MMX recommends the 4-pin pinned variant of this hub, which adds four aerospace-machined dowel pins for additional security.
What is included with the BMW N55 S55 crank hub upgrade? The kit includes the billet EN36 steel single-piece hub and a new OE-spec crank bolt for proper high-torque installation. The optional MMX Capture Plate, which secures the crank bolt against loosening from engine harmonics, is sold separately.
Do I need the Capture Plate as well? The Capture Plate addresses a separate failure mode from the crank hub itself. The BMW N55 S55 crank hub upgrade prevents hub-to-crank rotational slip; the Capture Plate prevents the crank bolt from gradually backing out due to engine harmonics. The two are complementary, and pairing both provides the most complete protection, though the hub alone resolves the primary slippage risk.
Can this be installed with the engine in the car? Yes. The BMW N55 S55 crank hub upgrade can be installed with the engine in situ, though access to the front of the engine is required and typically involves removing the front bumper or radiator depending on the specific model. Professional installation is recommended given the precision required.

About MMX Performance

MMX Performance is a UK-based specialist in performance parts for BMW and MINI vehicles, crafting high-quality upgrades that blend precision engineering, rigorous testing, and motorsport heritage. Driven by enthusiast culture, MMX designs its products in the UK and puts them through track validation to ensure durability, fitment accuracy, and on-road performance. Their catalog spans drivetrain components, spacers, hardware, and chassis enhancements, all tailored to elevate both the driving experience and visual appeal of BMW and MINI models.

Additional Information

The Bulletproof Automotive website contains many thousands of products purchased in multiple different currencies. All of the prices are entered manually and accurately at the time of entry. Due to the consistently fluctuating international exchange rates, at times prices may not be able to be honored at their original intended rate. We apologize for any inconvenience this may cause, unfortunately our website is unable to compensate dynamically for what can at times be volatile changes in the cost of items due to currency values fluctuating, changes in prices from suppliers, changes in shipping and import duties, and other factors. Rest assured that any order you place on line will be at zero risk to you in this area. If in the event your order cannot be fulfilled at the original intended website price we will offer you a 100% refund, no questions asked. We will continue to do our best to maintain updated prices and we will always continue to offer our price match guarantees as well to ensure our prices are always the best for you. In short, prices may change without notice. It is always advised to give us a call prior to placing your order online to confirm availability and to confirm current pricing.

Shipping Policy

Items that are in stock in the US, either at Bulletproof’s warehouse or at a supplier’s warehouse, are generally delivered within 7-10 days. Special order items from overseas take considerably longer. As a courtesy Bulletproof offers delivery estimates to our customers which take into consideration manufacturer availability and shipping schedule. These estimates represent our best guess based on previous orders from the manufacturer and do not in any way imply a guaranteed delivery window. Many manufacturers work in a “just in time” inventory system and often take 2-20+ weeks to produce an item once an order is submitted. All deliverable items are then sent to our Japanese warehouse. Bulletproof ships a minimum of one full ocean freight container every month from Japan, oftentimes more than one a month. Ocean freight takes an average of 4 weeks. Typically it breaks down to one week in Japan for paperwork and customs, two weeks by boat and one week in US customs/clearance. Due to the wide number of variables between manufacturer and shipping schedules, delivery estimates are simply just that – estimates. We attempt to estimate conservatively and we usually deliver faster than our estimates suggest. It is not Bulletproof’s policy to guarantee delivery time of any special order item, this is impossible for us to do. By ordering you acknowledge that there is no required delivery ETA and an order may not be canceled or altered due to manufacturing or shipping delays, all ETA’s are provided as a best guess only. Please review the full Terms & Conditions here.

BP Pricing Difference

We do pricing a little differently on our JDM brands and we believe in making things simple and clear. No hidden fees or surcharges. Every price you see includes the shipping cost to our office in Los Angeles, California and all the associated taxes/duties/fees for bringing the products into the US. The only shipping you ever pay is from our facility in the US to your location. Be wary of resellers that don’t include the cost of international shipping in their pricing on JDM parts. While we believe we’ll always have the lowest all-in price on JDM products, we offer a price match guarantee for all authentic parts purchased from authorized dealers as well. For many international customers, it’s much more affordable to ship from the USA than from Japan directly, as the air freight and ocean freight costs are typically much less. However, for customers looking to ship directly from Japan outside of North America, or domestically in Japan, we can provide pricing specifically for that scenario. Please do not hesitate to contact us with any pricing questions or concerns. Please email us at sales@bulletproofautomotive.com with any inquiries.

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MMX Billet One-Piece Crank Hub Upgrade for BMW Vehicles (with N55 or S55 engine) [MMR20-1001/MMR20-1003FK]

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MMX Billet One-Piece Crank Hub Upgrade for BMW N55 and S55 Engines

Features

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Notes

Frequently Asked Questions

About MMX Performance

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