BMW S55 Crank Hub Guide: Failure, Symptoms & 4-Pin Upgrades

Introduction

The BMW S55 is the twin-turbo inline-six engine fitted to the F80 M3, F82 and F83 M4, and the F87 M2 Competition. It is a high-output unit that has earned a strong reputation in the performance community, but one area of the engine attracts more discussion than most: the crank hub and timing-drive arrangement.

Not every S55 will suffer crank hub slip. Many engines cover high mileages and significant power without incident. However, because of the potential consequences if timing does move, a large number of owners — particularly those running tuned or hard-driven cars — choose to fit a pinned crank hub upgrade as a preventative measure.

This guide explains what the crank hub does, why it is considered a weak point, what symptoms to look for, and how the Insane Performance 4-pin upgrade works. It also covers what is involved in professional installation at Swift Performance.

What Is the BMW S55 Crank Hub?

The crank hub forms part of the connection between the crankshaft and the engine’s timing-drive components. It sits at the front of the crankshaft and provides the interface through which the timing chain drives the camshafts.

Keeping crankshaft and camshaft timing correctly synchronised is fundamental to engine operation. The engine management system relies on accurate timing signals to control fuelling, ignition and valve events. If the relationship between the crankshaft and camshafts shifts, the engine will not run as intended — and in more serious cases, internal damage can result.

Why Is the S55 Crank Hub Considered a Weak Point?

The factory arrangement relies primarily on clamping force and friction to hold the hub in its correct position on the crankshaft. Unlike some engine designs that use a key or spline to create a positive mechanical connection, the S55 hub depends on the clamping load of the crankshaft bolt and the friction between mating surfaces.

Under sustained high load — particularly at elevated torque levels — there is a possibility that the hub can move relative to the crankshaft. When this happens, engine timing shifts from its intended position. This is what is commonly referred to as a slipped or spun crank hub.

It is worth noting that this is not a universal failure. Many S55 engines run without issue. The concern is the nature of the consequences if it does occur, which is why the upgrade has become widely discussed.

Symptoms of an S55 Crank Hub Slip

If the crank hub moves, the engine management system will typically detect a discrepancy between crankshaft and camshaft positions. Possible symptoms can include:

Drivetrain malfunction warning on the dashboard
Engine management warning light
Camshaft or crankshaft timing fault codes stored in the ECU
Reduced power or limp mode
Rough or irregular running
Starting difficulties in some cases

It is important to note that these symptoms can have a number of other causes. Their presence does not automatically confirm that the crank hub has slipped. Proper diagnostic work is required to identify the root cause.

What Happens if the Crank Hub Slips?

The outcome depends on how far timing moves and how quickly the issue is identified.

A small amount of movement may result in fault codes, warning lights and poor running, with the engine entering a protective mode. In these cases, catching the problem early and addressing it promptly is important.

More significant timing movement creates the potential for valve-to-piston contact. In a high-compression, high-revving engine such as the S55, this can result in serious internal damage. The extent of any damage will depend on the specific circumstances.

This is why many owners treat the crank hub upgrade as a worthwhile preventative step rather than waiting for a problem to develop.

Does Every S55 Need a Crank Hub Upgrade?

No. Many S55 engines operate without crank hub problems throughout their working lives. The upgrade is not a compulsory requirement for every owner.

The decision to upgrade preventatively tends to depend on a combination of factors:

How the vehicle is used — road, track days or competition
Current power and torque output
Whether tuning is planned
The owner’s general approach to preventative maintenance
Appetite for risk given the potential consequences

For owners who use their car hard, plan to tune it, or simply prefer to address potential weak points before they become problems, the upgrade is a logical consideration.

Stock vs Tuned S55 Cars

Crank hub upgrades are particularly common on modified S55 vehicles. Tuning can significantly increase power and torque output, which places greater demand on the timing-drive components and increases the load through the crank hub interface.

That said, tuning does not guarantee crank hub failure, and standard cars are not automatically immune. The factory arrangement can be adequate for many applications. The upgrade is most frequently discussed in the context of tuned cars because the risk profile changes as output increases.

If you are planning a significant tune, addressing the crank hub beforehand is a sensible point to consider as part of the build.

How Does a Pinned Crank Hub Work?

A pinned crank hub upgrade replaces the factory friction-based arrangement with one that includes a positive mechanical connection between the crankshaft and the hub.

The process involves precisely drilling the crankshaft using a purpose-made fixture to ensure accurate positioning. Pins are then installed that create mechanical locating points between the crankshaft and the upgraded hub. This reduces reliance on clamping force and friction alone to maintain the hub’s position.

The crankshaft drilling must be carried out accurately. Incorrect drilling depth, angle or positioning can cause problems, which is why the quality of the fixture and the care taken during installation are important.

What Is the Best Crank Hub Upgrade for the BMW S55?

There are several established approaches to the S55 crank hub upgrade. These include pinned designs, keyed designs, one-piece hubs and capture-plate arrangements, with pinned solutions available in both 2-pin and 4-pin configurations. Each has its proponents within the S55 community, and the question of which represents the best S55 crank hub upgrade does not have a single universal answer.

Swift Performance’s preferred solution is the Insane Performance one-piece 4-pin crank hub. The BMW S55 4-pin crank hub mechanically locates the upgraded hub to the crankshaft at four points, creating a positive mechanical connection rather than relying solely on the factory friction-based arrangement.

Why Does Swift Performance Use a 4-Pin Crank Hub?

Our choice of the Insane Performance 4-pin crank hub is based on our own workshop experience rather than a belief that a 4-pin design is automatically superior to every other crank hub solution.

We have fitted the Insane Performance 4-pin system successfully to S55-powered vehicles and it is a system we know, understand and have confidence in. To date, we have had no issues with the Insane Performance 4-pin crank hub installations completed through our workshop. Because the system has worked consistently for us, we see little reason to change away from a tried-and-tested solution simply because alternative designs exist.

Other established 2-pin, pinned and keyed crank hub solutions are available and may be used successfully by other specialists. We are not in a position to make universal comparisons with every product on the market, and we would not suggest that our preferred choice is the only valid one. For Swift Performance, the Insane Performance one-piece 4-pin crank hub remains our preferred S55 crank hub upgrade based on our own installation experience.

What Is the Best Crank Hub Upgrade for a Tuned S55?

There are several established crank hub solutions available for the S55, and we would not suggest that a 4-pin design is automatically better than every 2-pin or keyed alternative. The best crank hub upgrade for a tuned S55 will depend on the installer, their experience and the specific solution they work with.

When customers ask Swift Performance what we recommend for a tuned M2 Competition, M3 or M4, our preferred solution is the Insane Performance one-piece 4-pin crank hub. That recommendation is based primarily on our direct workshop experience. It is a system we know, have fitted successfully and have found reliable in the vehicles we have installed it on. For us, there is little benefit in changing away from a proven solution simply because another design exists.

It is also important to note that installation quality matters as much as product choice when it comes to any S55 crank hub upgrade. Key factors include:

Accurate engine timing throughout the process
Correct crankshaft positioning before drilling
Precise drilling using the correct fixture
Correct use of the drilling fixture to ensure accurate pin placement
Sump removal to allow proper access
Thorough cleaning and inspection after drilling

The best crank hub for a tuned S55 is only as good as the installation behind it.

The Insane Performance 4-Pin S55 Crank Hub

Swift Performance uses and supplies the Insane Performance one-piece 4-pin crank hub. The manufacturer specifies a heat-treated steel, one-piece CNC-machined design intended to provide a more robust connection than the factory arrangement.

The kit includes:

One-piece CNC-machined crank hub
Uprated crankshaft damper bolts
Purpose-made drill bit
Precision drilling fixture
OEM BMW crankshaft bolt

Component Only – £799 Inc VAT

Customers who only require the hardware — for example, those fitting the kit at their own workshop — can purchase the Insane Performance BMW S55 4-Pin Crank Hub for £799 including VAT.

View the Insane Performance S55 4-Pin Crank Hub – £799

Why Swift Performance Always Removes the Sump

Drilling the crankshaft produces metal swarf — fine drill shavings that must not be left inside the engine. Some installation approaches leave the sump in place, which can reduce labour time but limits access for cleaning and inspection after drilling.

At Swift Performance, we always remove the sump as part of the crank hub installation process. This gives us proper access to clean the area thoroughly after drilling and to inspect the lower end of the engine before reassembly. Our aim is to minimise the risk of metallic debris remaining inside the engine.

Our standard procedure includes:

Sump removal and refitting
Cleaning and inspection of the area after drilling
Replacement sump gasket
Relevant sump and oil-pump fixings
Fresh engine oil
New S55 oil filter

S55 Crank Hub Installation at Swift Performance

Correct installation requires specialist timing equipment, accurate crankshaft positioning, precision drilling using the correct fixture, and careful reassembly. It is not a job that should be approached without the appropriate tools and experience.

£1,950 including VAT – supplied and fitted

This price includes the Insane Performance 4-pin crank hub kit, all associated consumables, sump removal and refitting, fresh oil and filter, and full installation at our workshop.

Current typical lead time: approximately 5 weeks
Vehicle required at the workshop: two working days

The two-day period allows time for installation, reassembly, checks and a test to confirm correct operation before the vehicle is returned.

View our £1,950 BMW S55 Crank Hub Supply & Fit Package

What Else Is Worth Doing at the Same Time?

The crank hub installation involves significant dismantling of the front of the engine. While the car is apart, some additional work can be carried out with reduced extra labour compared to doing it as a standalone job. None of the following is compulsory, but it is worth considering if any of these items are due or relevant to your build:

ACL rod bearings
Camshaft alignment check
Spark plugs
DO88 S55 charge pipes
DO88 S55 J-pipe
Sports catalysts
Intake upgrades
Minor servicing items
Insane Performance crank seal guard
Performance oil for tuned or track-use cars

If you are planning any of these alongside the crank hub, let us know when you get in touch and we can discuss what makes sense to combine.

Which BMW Models Use the S55 Engine?

This guide relates specifically to the S55 engine. It does not apply to N55, B58 or S58 applications. The S55 is fitted to the following models:

BMW F87

M2 Competition
M2 CS

BMW F80

M3
M3 Competition
M3 CS

BMW F82 / F83

M4
M4 Competition
M4 CS
M4 GTS

BMW S55 Crank Hub FAQs

Is the S55 crank hub actually a problem?
It is a known area of discussion within the S55 community. Not every engine is affected, but the potential consequences of timing movement mean many owners choose to address it preventatively.

Can a standard S55 spin the crank hub?
Yes, it is possible on a standard car, though it is more commonly associated with tuned or hard-driven vehicles. Standard cars are not automatically immune.

Does tuning cause crank hub failure?
Tuning increases the load on the timing-drive components, which changes the risk profile. It does not guarantee failure, but it is one reason why the upgrade is particularly common on modified cars.

What are the symptoms of a spun crank hub?
Common indicators include drivetrain malfunction warnings, engine management lights, timing-related fault codes, limp mode, rough running and, in some cases, starting difficulties. These symptoms can also have other causes.

Can a slipped crank hub damage the engine?
Depending on the extent of timing movement, there is potential for valve-to-piston contact and internal engine damage. Catching the issue early is important.

What does a pinned crank hub do?
It creates a positive mechanical connection between the crankshaft and the hub using precision-drilled pins, reducing reliance on the factory friction-based arrangement.

Why does Swift Performance use a 4-pin crank hub?
We use the Insane Performance one-piece 4-pin crank hub because it is a system we have direct workshop experience with and have found reliable in the vehicles we have fitted it to. We do not claim that four pins are inherently better than every 2-pin or keyed design; it is simply the proven solution we prefer to use.

Why does Swift Performance remove the sump?
Removing the sump gives proper access to clean and inspect the area after drilling, helping to ensure that metal swarf from the crankshaft drilling process is not left inside the engine.

How much does an S55 crank hub upgrade cost?
The Insane Performance 4-pin kit is available component-only for £799 inc VAT. Supplied and fitted at Swift Performance is £1,950 inc VAT.

How long does installation take?
The vehicle is required at our workshop for two working days. Current typical lead time from booking is approximately 5 weeks.

Should I do the crank hub before tuning my S55?
Many owners choose to address the crank hub as part of their build preparation before increasing power. It is a sensible point to consider, particularly if a significant tune is planned.

Conclusion

The S55 crank hub is a well-documented area of the engine that is worth understanding, whether you are running a standard car or planning a build. The decision to upgrade is a personal one based on your use case, power level and approach to preventative maintenance.

Swift Performance offers two options:

Component only:
Insane Performance S55 4-Pin Crank Hub – £799 inc VAT

Complete supply & fit:
Swift Performance S55 4-Pin Crank Hub Upgrade – £1,950 inc VAT

Installation is carried out at our workshop in Stoke Mandeville, Aylesbury, Buckinghamshire. If you have questions about the upgrade or would like to discuss your specific car, please get in touch.