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Crank Hub Upgrade: BMW F8x S55 M3 / M4

Crank Hub Upgrade: BMW F8x S55 M3 / M4 | Image 1

Are you concerned with a Crank Hub Timing Gear Failure on your F80 / F82 / F83 M3 or M4 BMW?

The Team at Redline Speed Worx (RSW) has recently completed the TPG Tuning Keyed Crank Hub Kit installation on our customer's BMW M4. We believe it to be a must-have upgrade to prevent the need for Crank Hub failure or repair.

The release of the most recent iteration of BMW’s iconic F8x M3 (and M4) was met with some trepidation... Lots of purists were up in arms over the fact that it was going to benefit from forced induction, while others were happy that at least it was back to BMW’s tried and true inline 6 layout. No matter which side of the fence you rest on the outcome is impressive.

425 hp, 406 ft lbs of torque, and 0-60 times hovering around 4 seconds flat for a rear wheel drive sports car is phenomenal.

BMW M4 Keyed Crank Hub Installation at RSW | Image 2

The problem is for us enthusiasts, we can never have enough of a good thing. Unfortunately in all of BMW’s infinite wisdom it appears much alike the rods in the E46, and bearing wear issues in the E9X (E90,E92,E93), the current F8X( F80,F82,F83) generation is not without its flaws either. Luckily for owners, the fix is considerably less costly than the previous models.

The issue with the S55 arises from the factory crank hub for the timing chain.

On most modern cars timing belts have been changed over to timing chains, allowing for greater reliability, greater longevity, and more exact tolerances. Having a metal chain riding on teeth allows for the timing between the camshafts and the crankshaft to be kept perfect, unless something goes wrong with the system.

BMW M3 F80 Crank Hub Replacement NJ | Image 3

This article is not meant to scare M3/M4 owners but merely to let them know that this is an issue that has occurred on a handful of cars already, some stock, some modified, but it appears more likely to happen on a modified car. According to TPG Tuning they believe the issue is going to be more common on heavily modified cars where the rate of acceleration is higher. What we mean by a higher "rate of acceleration" is simply that the engine is progressing through the rev range significantly faster than a stock car. The redline doesn’t have to be any higher nor does the car have to rev higher for this to occur.

BMW M4 Keyed Crank Hub Installation in New Jersey | Image 4

The force that’s transmitted to the hub via the timing chain overcomes the clamping force of the hub.

What happens is the nut that holds the crank hub on the crankshaft loses tension and the crankshaft and camshaft get out of time. If the hub spins enough, it can cause the piston to smash into the valves. Luckily the guys down at TPG Tuning have engineered and produced a worthwhile solution using OEM BMW parts and some ingenuity.

Here is where the Hub sits usually, it has been removed for replacement and upgrade in this photo:

Installation of TPG Keyed Crank Hub at RSW | Image 5

The job isn’t extremely complex but does require a fair amount of  diss-assembly, including the intake plumbing, fuel supply, and valve cover.

BMW S55 Engine Repair at RSW Green Brook, NJ | Image 6

The Solution is taking the OEM BMW toothed hub, and cutting a relief to provide room for a locating key to hold the gear in place.

The ingenious part of the design is that in case for some reason tension was lost, the key will keep the hub located in the correct position on the crank, saving both the rods and pistons from catastrophic damage.

Key on TPG Tuning Hub:

RSW TPG Tuning Keyed Crank Hub F8x M3 M4 | Image 7

Keyway on Timing Gear:

BMW M4 Crank Hub Keyed Timing Gear | Image 8

The kit retails for $399.99 which, to us, is a bargain. Considering the reassurance it gives to those who intend on using their M3/M4 as it was designed to be used, driven hard, and potentially modified!

A $399.99 kit to keep a $40,000 engine safe is great value per dollar spent.

(replacement cost figure calculated off of parts for new long block and labor to swap it)

BMW S55 M4 / M3 Keyed Crank Hub Kit at RSW | Image 9

The kit includes:

  • Keyed OEM Crank Hub
  • Keyed OEM Crank Timing Gear
  • New OEM Vanos Bolts (Optional )
  • New OEM Valve Cover Gasket
  • New OEM Oil Pump Drive Gear with Friction Disc
  • New OEM Crank Bolt

If you have any questions regarding your specific vehicle, the kit, or installing it please Contact our Service Team directly!


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BMW , M3 , M4 , S55
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