Lot 12783: 2017 BMW M4 Competition

The listing doesn’t mention whether this 2017 M4 has had any crank hub work done, and that’s exactly the issue — this S55 engine is known for a documented crank hub problem.

Here’s the situation: The S55’s crank hub can spin on the crankshaft, which throws off timing between the crank and camshafts. This can range from rough running to catastrophic valve-to-piston contact (think $15K-$20K+ engine rebuild). It’s a well-known Achilles’ heel of this generation of M cars.

Does this specific car have the problem? There’s no indication in the dealer’s description that the crank hub has been addressed with an upgraded keyed hub, bolt capture plate, or pinning. At 84,521 miles, if it hasn’t been dealt with, you’re in the zone where these failures can occur — though some fail earlier, some never do with factory driving.

What you should do: Ask Auto 206, Inc. specifically:

• Has the crank hub been serviced or upgraded?
• Is there documentation of a keyed/pinned crank hub installation?
• If stock, has the crank bolt torque been checked?

If they can’t confirm it’s been addressed, I’d strongly recommend budgeting for a crank hub upgrade ($2,500-$4,000 at a reputable M specialist) or using it as a negotiation point. An S55 with a secured crank hub is a much more confident purchase.

Want me to show you similar M4 Competition models where the seller explicitly mentions crank hub service?