S55 Crank Hub - Should You Replace Yours?

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Last Updated: November 25, 2023

The BMW S55 engine is a high-performance, twin-turbocharged inline-six engine that debuted in 2014. This engine marked a significant evolution in BMW's M series, primarily used in models like the M3 and M4 vehicles and later on making its way into M2 Competition and CS cars. Here is the full list:

• BMW M2 F87 2015-2018
• BMW M2 Competition F87 2018-2021
• BMW M3 F80 - 2014-2019
• BMW M4 F82 - 2014-2020
  

Renowned for its exceptional power output and efficiency, the S55 represents BMW's commitment to advanced engineering and performance excellence. The engine is celebrated for delivering daily driving comfort and racetrack-ready dynamics, making it a favorite among enthusiasts.

I don't know about you, but I haven't really driven another 400hp+ car that can give you 30mph on a highway if you are behaving and cruising at the speed limit.

Choosing the Right Upgrade

Several aftermarket solutions are available to address the crank hub issue in BMW S55 engines. However, the only one I can recommend is the RK Autowerks S55 Billet Pinned Crank Hub. The simple reason is that I've gotten an inside look at the processes RK Autowerks goes through to produce any product, not just these crank hubs. I had the pleasure of rocking RK Autowerk's front-mounted carbon fiber intakes on my first F82 M4, and they were perfect.

Factors to Consider When Choosing an Upgrade:

• Quality: Opt for high-quality materials and manufacturing processes for durability.
• Reputation: Ensure that the manufacturer is reputable.
• Compatibility: Ensure the upgrade is compatible with your specific BMW model and any modifications it has.
• Cost: Consider the initial cost and potential long-term savings from avoiding future repairs.

Recommended Brands or Products

• RK Autowerks: Hands down the most knowledgeable BMW aftermarket performance part manufacturer.
• Gintani: Known name in the industry with good reputation. Offers one-piece crank hub.
• MMR Performance: Known for its one-piece billet crank hub.

Each brand and product has its unique features and benefits, so it's essential to research and choose the one that aligns best with your needs and expectations. Consulting with a trusted mechanic or automotive specialist can also provide valuable insights for making an informed decision.

Best S55 Crank Hub - 4 Pin Billet

RK Autowerks

Cost: $899.96 (was $1199.95)

Warranty: Lifetime through ECS Tuning

One Piece Crank Hub

Gintani

Cost: $1495.00

Warranty: Lifetime through ECS Tuning

Budget Friendly

MMR Performance

Cost: $798.52 (was $887.24)

Warranty: Lifetime through ECS Tuning

Introduction to the Crank Hub and Its Role in Engine Performance

The crank hub in an engine is a critical component that connects the crankshaft to the engine's timing gears and the oil pump. In the S55 engine, the crank hub ensures the synchronization of the crankshaft with the camshaft and the valve timing. This synchronization is crucial for the engine's performance, fuel efficiency, and emissions control. A well-functioning crank hub maintains the precise timing required for the engine to operate smoothly. However, in the S55, issues with the crank hub slipping can lead to timing problems, potentially causing severe engine damage and impacting the overall performance and reliability of the vehicle.

Understanding the Crank Hub in BMWs

Explanation of What a Crank Hub Is and Its Function in the Engine

The crank hub in an engine is a pivotal component that connects the crankshaft to vital parts like the timing chain and oil pump. It's responsible for maintaining the synchronized operation of the engine's moving parts. In high-performance engines like BMW's S55, the crank hub is critical in ensuring accurate valve timing, which is crucial for optimal engine performance, efficiency, and longevity.

Specific BMW Models Known to Have Crank Hub Issues

Crank hub issues are particularly noted in certain BMW models equipped with the S55 engine, predominantly the M3 and M4 and, to some extent, the M2 Competition. These models, celebrated for their high performance, have faced challenges with the crank hub component, leading to a broader discussion among owners and enthusiasts. It is also worth noting that the crank hub issue was not as common in the 2015 model S55 engines.

Symptoms and Risks of a Failing Crank Hub

The symptoms of a failing crank hub in these BMW models include:

• Engine Misfires and Performance Issues: As the crank hub fails, it can cause the engine's timing to becomes erratic, leading to misfires and reduced performance.
• Unusual Engine Noises: Clicking or knocking sounds from the engine area can indicate a crank hub problem.
• Check Engine Light: The car's onboard diagnostics may detect timing discrepancies, triggering a warning light.
• Severe Engine Damage: In worst-case scenarios, a failing crank hub can lead to significant internal engine damage, such as bent valves or damaged pistons, due to timing misalignment.

Why Should You Upgrade Your S55 Crank Hub?

Increased Reliability and Peace of Mind

Upgrading to a more robust crank hub design significantly reduces the risk of the hub slipping, a common issue in the stock S55 crank hub. This upgrade brings a sense of security, especially for BMW owners who use their vehicles for high-performance driving or have made engine modifications.

Some drivers have been driving their vehicles that have S55 engines for years without anything happening to them. I, myself, have had the M4s for a combined 4 years and haven't even had a scare of S55 crank hub failing. But at the end of the day, it's a known problem, so being out of warranty and not changing it might result in extremely large repair bills.

Improved Engine Performance and Power Handling

A stronger crank hub can better handle increased power and torque, a typical outcome of engine tuning. This ensures that engine modifications to boost performance do not compromise the engine's integrity.

Potential to Prevent Costly Repairs Down the Line

Investing in an upgraded crank hub can be a cost-effective decision in the long run. Preventing the crank hub from failing averts severe engine damage, which can be exceedingly expensive to repair. This proactive approach can save BMW owners from hefty repair bills and extended vehicle downtime.

Why You Might Not Be Sold on The S55 Crank Hub Upgrade

Why the Stock Crank Hub May Be Inadequate

The stock crank hub in certain BMW models, particularly those with the S55 engine, must show more accuracy due to its design. The standard crank hub is a three-piece unit that relies on friction plates to maintain alignment. Under high stress or performance conditions, these plates can slip. This slippage disrupts the engine's critical timing, leading to potential engine failures. The situation is exacerbated in tuned or modified engines that operate under higher power and torque, increasing the strain on the crank hub.

When Do These BMW S55 Engine Crank Hubs Fail: Common Cases

Common patterns when S55 crank hubs usually fail:

• High-Performance Stress: In several instances, BMW owners with tuned or heavily modified engines experienced crank hub failures. These failures often occurred during high-stress scenarios like aggressive acceleration or track driving, leading to catastrophic engine damage.
• Random Failures in Daily Driving: Some BMW owners reported crank hub issues under normal driving conditions, highlighting the unpredictable nature of these failures. In these cases, the sudden loss of engine timing led to costly repairs and safety concerns.

The reasoning to not get the crank hub changed based on the things mentioned above would be that your engine isn't tuned, or that you may be one of the lucky ones that will never have crank hub issues during your ownership of the vehicle. For the time being, I fit both criteria's. However, once my extended warranty expires, I will surely get the crank hub replaced.

S55 Crank Hub Upgrade Cost

Breakdown of Costs Involved in Upgrading

• Parts: The cost of the crank hub upgrade kit can vary but typically stays around $1000.
• Labor: Professional installation can cost between $1000 to $3000, depending on your location and labor rates.
• Additional Expenses: Potential extra costs for related parts like gaskets or seals.

In total, the average price range to upgrade S55 crank hub that I'm seeing people mention falls between $2000 and $3000 out the door.

Comparison with the Cost of Not Upgrading

• Engine Repairs: Failure of the crank hub without an upgrade can lead to severe engine damage, with repairs costing up to the full price of a new engine.
• Long-Term Value: Upgrading can prevent costly engine overhauls and maintain the vehicle's value.

Upgrading the crank hub can be an investment but is often more cost-effective than facing the high expenses of major engine repairs due to a failed stock crank hub. From what I'm seeing in listings of BMW M2, M3, M4 that are for sale, people are much more inclined to purchase one of those BMWs that have S55 engine if they have gone through the crank hub upgrade already. Also, keep in mind that BMW M3 F80 crank hub will be the same as the BMW M4 crank hub.

Post-Upgrade Considerations

Break-In Period and Care

• Gentle Use: Avoid high-stress driving, like aggressive acceleration or high RPMs.
• Observation Period: Monitor the car's performance closely for the first few hundred miles.

Monitoring and Maintenance Tips

• Regular Checks: Inspect the crank hub area for any signs of oil leaks or unusual noises.
• Scheduled Maintenance: Stick to regular maintenance schedules, ensuring engine components are in good condition.

Signs of Successful Installation

• Smooth Operation: The engine runs smoothly without unusual vibrations or noises.
• No Warning Lights: There are no engine-related warning lights on the dashboard.
• Consistent Performance: The car maintains consistent performance without timing issues or misfires.

Proper post-upgrade care ensures the longevity and effectiveness of the crank hub upgrade, maintaining the high performance of your BMW.

S55 Crank Hub Upgrade or Replace: Bottom Line

Upgrading the crank hub in certain BMW models, particularly those with the S55 engine, is more than a preventative measure—it's an investment in the car's performance and reliability. If your BMW is out of warranty, then the cost of upgrading pales compared to the potential expenses and safety risks associated with a failed crank hub. For BMW enthusiasts and owners, taking proactive steps to address this known issue ensures peace of mind and preserves the vehicle's integrity and value. Remember, mechanical worries should never overshadow the joy of driving your BMW. Consider this upgrade as a key to unlocking the full potential of your BMW experience.