Known issue · S55 engine

The S55 crank hub, explained for buyers.

The short answer: on a stock F80 M3, F82 or F83 M4, or M2 Competition, the crank hub is a known risk, but a lower one. On a tuned car, budget $2,000 to $4,000 for an upgraded hub, or walk away. Below is what the part does, how real the risk is and how to buy around it.

ContentsJump to a section

What it is

The crank hub drives the S55's timing chain from the crankshaft. It is held on by friction alone: no key or pin locks it in place. Under high torque, most often on cars tuned beyond stock power, the hub can slip on the crankshaft.

When it slips, engine timing goes with it

Best case is a warning light, misfires and a tow; worst case is contact between valves and pistons and a very expensive engine.

Which cars this applies to

F80 M3 (2015 to 2018)
F82 M4 and F83 M4 Convertible (2015 to 2020)
F87 M2 Competition (2019 to 2021) and M2 CS (2020)

The first M2, with the N55 engine, uses a similar hub. It makes less torque, so its hub rarely slips unless the car is tuned.

The S55 cars by model year

F80 M32015 to 2018

F82 M42015 to 2020

F83 M4 Convertible2015 to 2020

F87 M2 Competition2019 to 2021

F87 M2 CS2020

The S58 generation that followed, the G80 M3, G82 M4, and G87 M2, does not share this design and has no crank hub worry of its own so far.

How big the risk really is

Documented failures cluster on tuned cars, and the harder the tune, the higher the risk. Stock cars are widely considered lower risk. Mporium BMW, a specialist that fits the upgrade, says it has seen only a few failures on stock engines and more on engines with added power.

That is why our reliability rating for the S55 reads: solid in stock form, with the headline risk being tune-correlated. It is a known, manageable risk and no reason to skip the platform.

The fix and the cost

$2,000 to $4,000

The budget for a pinned or upgraded crank hub, installed at an independent specialist

The preventive fix is a pinned or upgraded crank hub, which mechanically locks the hub to the crank.

Tip

On a tuned car, many buyers treat it as mandatory and, if it has not been done, negotiate it into the price.

What to ask the seller, in order

0 of 4 ticked

1Has the car ever been tuned, flashed, or run above stock power?Even briefly, even by a prior owner.
2Has a pinned or upgraded crank hub been installed?Ask for the receipt and the shop name.
3If tuned and unpinned: price the car as if the $2,000 to $4,000 job is yours to do, because it is.
4On any S55, get a pre-purchase inspection from a BMW specialistAsk them to scan for camshaft-to-crankshaft timing faults.

Your ticks are saved in this browser.

The bottom line

A stock, documented S55 car with a clean history is a strong buy, and our scores treat it that way. A tuned car without crank hub work is a negotiation opportunity with a known number attached.

The buyers who get hurt are the ones who did not ask. Each affected car's generation page, linked above, lists every other known issue as well.

Questions and answers

What is the S55 crank hub issue?

The S55 engine's crank hub can slip, most often on tuned cars running above stock power. A slipped hub throws the engine timing and can cause serious engine damage. Preventive fixes (a pinned or upgraded hub) run $2,000 to $4,000 installed at an independent specialist.

Which BMW M cars have the S55 crank hub risk?

Cars with the S55 engine: the F80 M3 (2015 to 2018), F82 M4 (2015 to 2020), F83 M4 Convertible (2015 to 2020), and the F87 M2 Competition (2019 to 2021) and M2 CS (2020). The earlier N55-powered M2 uses a similar friction hub; with less torque, it rarely slips unless tuned. The S58 cars that followed (G80, G82, G87) do not share the design.

Is the crank hub a problem on stock S55 cars?

Documented failures cluster heavily on tuned cars pushed beyond stock power. Stock cars are widely considered lower risk, though the community debates how low. The risk rises with the tune, so it varies from car to car.

What should I ask a seller about the crank hub?

Ask about tune history, whether the car has ever run above stock power, and whether a pinned or upgraded crank hub has been fitted, with receipts. Treat a heavily tuned car without crank hub work as higher risk and price accordingly.

Sources

Specialist shops that fit the upgrade are the main public source on this issue, so read their numbers as estimates. Model years are from the EPA's fuel economy listings. Sources checked September 2026.

Keep reading