S55 Crank Hub: Buyer Beware

IA EURO illustration of the BMW S55 crank nose: damper, hub, grip disc and chain sprocket on the crankshaft, held by one bolt at 100 Nm plus 270 degrees; friction only, no key, no pin

Every S55 holds its timing chain sprocket on the crankshaft with friction, not a key. Most never slip. When one does, the cams fall out of time with the pistons, and the bill runs from a re-time to a cylinder head. This is what BMW's own documents say, what nobody has proven, and how to buy an M car without buying the problem.

Which cars

F80 M32015 to 2018, including Competition.

F82 and F83 M42015 to 2020, coupe and convertible, including Competition, CS and GTS.

F87 M2 Competition and M2 CS2019 to 2021. The plain 2016 to 2018 M2 has the N55, which uses the same hub, washer and sprockets.

How BMW built it

There is no key, no spline and no pin on the S55 crank nose. Three parts sit on a plain round shaft: the oil pump drive sprocket, the timing chain sprocket and the hub that carries the vibration damper. One bolt clamps the whole stack, with grip discs between the faces. BMW's repair text says it plainly: release that bolt and the sprockets are no longer held to the crank, and the camshafts can turn on their own.

Friction onlyClamp force from one bolt is the only thing keeping the cams in time with the crank. If that friction lets go, the timing moves.

Central boltM18 x 108, grade 12.9

BMW torque100 Nm (74 lb-ft) + 270°

To break it looseOver 600 Nm (443 lb-ft)

ReuseNever. New bolt every time

BMW goes further than the bolt. Every time it's released, BMW says to renew four parts: the bolt, the loose grip disc, the oil pump sprocket with its welded-on grip discs, and the timing chain sprocket. BMW also says the engine is damaged if those friction plates are damaged or missing. One BMW job lists the break-loose torque as about 500 Nm instead of 600. Either way, a correctly installed bolt takes a 3/4 inch drive to move.

This is a family design. The hub, the loose disc and both sprockets carry the same BMW part numbers as the N55. The S55's only unique part on the nose is the damper.

What a slip looks like

Drivetrain Malfunction on the dash, a check engine light and limp mode. Owners and shops report this as the usual first sign.
Rough running, misfires, power loss, a hard start or no start.
Codes: BMW defines 130E20 and 130F20 (camshaft offset to crankshaft out of tolerance) on its newer engines. Shops report them on slipped S55s. BMW hasn't confirmed which codes the S55 sets for this.

Damage ranges widely. The best documented teardowns we found are one shop's two cars. One was re-timed and driven away with no engine damage. The other had 12 bent exhaust valves and needed head work. Both were tuned.

IA EURO illustration traced from a forum member's photo of a slipped S55 crank hub: the polished band shows where the parts turned against each other — Traced from a forum member's photo of a slipped S55, shared on Bimmerpost. The polished band is where the parts turned against each other.

What BMW has said: nothing

We found no recall, no service bulletin, no warranty extension and no redesign for this. We checked every recall on the M2, M3 and M4 from 2015 to 2020 (10 campaigns, none about the engine timing) and 325 service bulletin records filed with NHTSA. BMW did publish other S55 engine bulletins, so it isn't that the engine went undocumented. BMW's parts catalog through late 2019 shows the same hub part number on every S55, including the M4 GTS, M4 CS and M2 Competition. Forum claims that BMW "fixed it" on later cars don't hold up in BMW's own parts data.

BMW's own job for replacing the hub takes the engine out of the car.

How often: nobody knows

There is no verified failure rate. Not from BMW, not from any survey we could find. Numbers online run from under 0.1 percent to 20 percent, and none of them shows its data.

Government complaints: 13 of 64 owner complaints filed with NHTSA on the M3 and M4 name the crank hub. 11 of those 13 were filed on December 18 and 19, 2019, a month after a popular YouTube video. That counts awareness, not failures.
Stock vs tuned: both documented teardowns were tuned cars. Owners also report slips on stock cars, including a 2018 M3 at 2,300 miles that was reportedly fixed under warranty. None of those are verified either way.
The power line: "over 500 lb-ft" or "Stage 2" gets repeated a lot. Nobody has data for any threshold. Same for E85: named often, never measured.

Our read: more torque means more load on a friction joint, so a tuned S55 with no hub upgrade carries more risk than a stock one. That's engineering sense, not a statistic. Anyone quoting you a percentage is guessing.

The fixes

BMW has no approved pinned or keyed hub. Every fix below is aftermarket, and every claim about strength comes from the company selling it. No independent test data exists for any of them.

Pinned hubHoles are drilled into the crank nose and pins lock the hub to it. A permanent change to the crank.

One-piece billet hubHub and timing sprocket made as one part, usually keyed to the oil pump gear and pinned to the crank. Removes the loose friction discs.

Spline lockA hardened one-piece hub whose splines bite into the crank nose under clamp load. No drilling. The maker says it needs a bolt capture plate with it.

Capture plate aloneLocks the bolt head so the bolt can't back out. It doesn't change the friction stack. Most sellers, including one plate maker, say it isn't a full fix on its own.

Hub kits, US$945 to $1,240

Installed, published shop pricesFrom $1,750 to $2,000

All in, owner reports$3,000 to $5,000

Prices read from vendor and shop pages on October 20, 2026. The spread is mostly what else gets done on the same visit. Most shops do it with the engine in the car: oil pan, valve cover and front crank seal off, then a full re-time. One kit maker quotes 18 hours. BMW's own hub job pulls the engine. Re-timing it wrong bends valves, so this is a shop with S55 timing tools, not a driveway job.

Buying one: paper first

Hub done? Get the invoice: hub brand, shop, date, mileage. "Already done" with no invoice counts as not done.
A real hub job leaves BMW parts on the bill: central bolt 11 21 7 614 270, grip disc 11 23 8 090 136, oil pump sprocket 11 41 8 091 535, timing sprocket 11 31 7 502 180 and a front crank seal.
Any tune at all? Flash, piggyback, E85, turbos, downpipes. Ask for the tune invoice and dyno sheets. A car flashed back to stock is still a car that was tuned.
History: any Drivetrain Malfunction, limp mode, tow-in, head or valve work. Ask what was found.

Buying one: on the car

Full code scan, stored and history: camshaft, VANOS, crank sensor and misfire codes. A clean scan doesn't clear the hub. A small slip can store nothing.
BMW's timing check is mechanical: valve cover off, crank locked at top dead center, gauges on the cam flats. Gauges flat means in time. It's a shop job, worth it on a tuned car you're serious about.
Unverifiedowners say a capture plate can be seen with a light and mirror behind the front air box, and a billet hub looks shiny and one-piece through a borescope at the oil filler. Paper still wins.
No inspection allowed by an S55 shop? Walk.

Questions for the seller

Has the crank hub been upgraded? Which brand, which shop, when, at what mileage? Can I see the invoice?
Has it ever shown Drivetrain Malfunction, gone into limp mode or been towed in?
Any engine, head or valve work? Why?
Is it tuned now, or was it ever? Who tuned it, which map, still on it?
DCT or manual? Track days, launches, missed shifts, over-revs?
Can my shop scan it and check the timing before I buy?

Price it in. Not done and you plan to tune it? Budget the hub job, $1,750 to $2,000 at published shop prices, before you agree on a number.

Read our S55 engine guide →

BMW facts come from BMW's repair instructions and parts catalog for the S55 and N55, and BMW's US recall and bulletin filings with NHTSA. Complaint counts come from NHTSA's public complaint data, pulled October 20, 2026. Shop and owner reports are labeled as such. Hub prices are from vendor and shop pages read the same day.