EnginesN54 N55 S55

Splined crankhub install: the no-drill conversion, pressed and broached in the car

The splined crankhub install on N54/N55/S55: the old-bolt press, the 75 ft-lb stage, factory torque-plus-angle, the bolt-capture companion, and the verification checklist.

11 min readUpdated 2026-10-20Rapid Racing

Press, mark, angle — our schematic, drawn for this guide

This is the install canon for the splined crankhub conversion — the VTT-class no-drill kits for the N54, N55 and S55. The conversions guide owns the decision (pinned vs splined vs stock, the failure anatomy, the honest comparison); this page owns the wrenching. The sequence below is the vendor's install guide paraphrased and labeled, never copied — the sheet in your kit box governs, kit revisions change, and every vendor claim stays marked as a vendor claim. The factory numbers here (the central-bolt torque-plus-angle law, the VANOS bolt specs) trace to the factory documents cited below and are carried in full on the engine pages.

What comes in the box

Per the vendor's packing list: the splined hub itself; an OEM oil sprocket and its retainer (optional items); an OEM crank bolt (optional — if your kit ships without, you supply a fresh one, always); the crank bolt capture (optional line item, required companion — below); and six to eight capture bolts with washers. Check every bag against the list before the car comes apart; the vendor's own first instruction is to verify nothing was lost in shipping, and their contact-first policy for anything missing or that does not fit is the right instinct — this kit is plug-and-play only when the instructions are followed exactly.

The bolt-capture requirement, stated honestly

The splined hub converts the crank-to-hub drive from friction to a mechanical lock — but the joint is still clamped by the factory central bolt, and bolt back-off is the second failure path, untouched by splines. The vendor's response: the capture is part of the system. Their install sequence's final step installs it onto the damper, and their positioning is that the splined hub is not intended to run without one.

The honest read: required companion, not an upsell. It shows as an optional line in the packing list only because the kit sells in several configurations (hub only, hub with sprocket, hub with sprocket and capture). If your configuration omits it, buy it separately — the capture has its own install guide in this series, and on this job it costs minutes because the front is already apart.

Prerequisites: the honest list

The vendor's own header for this install is blunt — qualified technician, special tools, intimate knowledge of the BMW cam-to-crank timing system, and if you are even remotely concerned you cannot install it correctly, do not attempt. A first-time DIYer on the S55 documented roughly 60 hours spread over multiple weekends and succeeded — with a second car, every special tool bought in advance, and a 90-minute walkthrough studied beforehand. That is the honest shape of this job in a home garage.

Tools and access beyond the engine-page list:

The full factory timing kit — cam locking fixtures, TDC pin, and critically a flywheel locking tool that engages the ring gear, not just the TDC pin. The breakaway torque on the central bolt (S55: the factory document says it exceeds 600 Nm; the pinned-kit vendor says over 440 lb-ft; a DIYer read over 500 Nm off ISTA) will spin an unlocked crank into the valves or launch a pin-only setup across the garage.
A very long breaker bar and a 22 mm socket (half-inch drive; 7/8 inch works in a pinch) for the press stage; a 3/4-inch drive for the S55 breakaway.
Torque wrenches that read accurately at the low end — the timing stages live at single-digit newton-meters.
An engine support cradle and lift access if the pan comes off in the car (subframe drop territory on some chassis).
Fresh one-time hardware before you start: oil pan gasket and bolts, valve cover gasket, VANOS gear bolts, front crank seal, coolant and oil. The vendor's parts list per engine (pan gaskets, VANOS bolts, and on the S55 the oil chain tensioner and its non-reusable access cap) is worth ordering in one shipment with the kit.

The install sequence

Vendor instructions, paraphrased. The sheet in your kit governs; the engine pages carry the factory procedures this sequence assumes.

Access. Follow the factory procedures to strip the front: under trays, radiator fan, serpentine belt, valve cover, vibration damper, oil pan (the vendor suggests pan-off; pan-on is possible but very difficult and not recommended). The engine pages carry the damper and chain procedures this rides on.
TDC and locks. Find TDC, lock the cams with the timing tools, then install the crank locking tool. If the hub has already slipped, be very careful rotating the motor — the crank can turn under the cams and bend valves. Never remove the central bolt without the crank locked; the vendor's capital letters are earned.
Break the bolt, strip the stack. Chain tensioner out to relax the chain, then the central bolt, hub and timing sprocket come off the front. If you are replacing the oil sprocket and retainer (recommended), the retainer pries out with a screwdriver and the sprocket squeezes past, relieving oil-pump chain tension as needed.
S55 oil-chain tensioner warning. Removing the oil sprocket can let the oil chain tensioner piston pop out of its bore — and per the vendor it is very hard to reseat without damaging it. Have a new tensioner and the non-reusable access cover on hand. (A DIYer skipped this, watched the piston spring into the oil pan, and spent quality time with a magnet.)
Prep the nose. Brake-clean the crank snout and check for burrs or damage, especially if the hub ever slipped — the crank must be in good shape to accept the splines. Degreased, undamaged, dry.
Front crank seal. If it is being renewed, now is the time — the hub is out and the seal bore is exposed.
Install the oil sprocket (gear side toward the engine), retainer, and on the S55 the new oil tensioner if this is the moment for it.
The chain trap — read this twice. The chain must be routed around the hub before the hub goes on. Miss it and the hub comes back off with a puller, because once pressed, it is pressed. The vendor's easier path in the car: remove the two VANOS solenoids (their one-time bolts are replaced at the factory spec, 20 Nm + 180°) so the chain drops, install the hub, then pull the chain back up.
Lubricate the seal lip (white grease or similar) so the hub slides through without cutting it. Slip the hub through the seal and the oil sprocket to the crank nose.
The press — the heart of the install. Keep the hub flat against the nose: the crank taper is aggressive and self-centers, but the hub can go on cocked if you let it. Hand-start the old central bolt (your previous bolt — its job is to be a press tool, and it goes to the bin afterwards). Lock the crank. Then, with a half-inch ratchet and 22 mm socket, tighten the old bolt until it stops. This is the self-broaching stage: the hub's splines (vendor-hardened to around HRC 60 against their published crank-nose reading around HRC 23) are cutting their own teeth into the nose as you go. Expect real, sustained force — this does not feel like seating a stock hub, and it is not supposed to.
Confirm the hub is fully in. Hub face flush at the nose, no proud edge, ratchet taking no more movement.
New bolt, 75 ft-lb. Old bolt out, fresh factory bolt in, torque wrench: 75 ft-lb (about 102 Nm). You are not done — the stretch comes later. Mark the bolt head to the hub now (you will track the angle stage by this mark) and mark one damper bolt hole so the capture's clocking lands easily later.
Time it. VANOS sprockets on with the pins aligned into the plates, TDC still held, two new VANOS bolts hand-tight only. Pre-tension the chain with the tensioner tool — the vendor sheet says 3 Nm here and warns too much breaks the chain guides; note the factory procedure for this same step specifies 0.6 Nm, and that divergence is worth a question to your kit vendor before you wrench. Then the VANOS bolts to the factory 20 Nm + 180°.
The verification loop. Crank bolt tight, VANOS tight, all timing tools out except the tensioner tool — rotate the engine in its normal direction back to TDC. Reinstall the timing tools and confirm timing held. If it did not: new VANOS bolts again (they are one-time), retime. Only when timing verifies does the tensioner tool come out and the factory tensioner go back in.
The stretch. Crank or flywheel properly held, recheck the 75 ft-lb, then with a very long breaker bar turn the angle: 360° on the N54, 270° on the N55/S55 — the factory angle stage, tracked with your paint mark. The long bar is not theater; angle-stretching a 12.9 bolt to the factory spec takes serious leverage.
The capture. Reassemble in reverse — every one-time bolt renewed — and install the crank bolt capture onto the damper with the provided bolts and washers at 40 ft-lb (about 54 Nm) per the vendor sheet. The damper-hole mark from step 12 is why this drops on instead of forcing the clocking.

Factory service documentN54 crankhub central bolt — the factory torque-plus-angle this install ends withOpens in your account's service knowledge — sign-in required.

Stage	Tool	Value (per the vendor sheet / factory spec)
Press, old bolt	1/2-inch ratchet, 22 mm	Until it stops — no torque value exists for this stage
New bolt pre-torque	Torque wrench	75 ft-lb (~102 Nm)
Angle stretch	Very long breaker bar	+360° (N54) / +270° (N55, S55) — factory spec
Chain pre-tension at timing	Tensioner tool	3 Nm per the vendor sheet; factory procedure says 0.6 Nm — flagged above
VANOS bolts (new)	Torque wrench + angle	20 Nm + 180° — factory spec
Capture bolts on damper	Torque wrench	40 ft-lb (~54 Nm)

The gotchas the threads teach

The puller law. Everything about this install is reversible until step 10. After the press, hub removal is a puller job — which is also why the chain routing in step 8 matters twice.
Cocked hub. The taper self-centers only if you let it. A hub pressed in crooked broaches crooked splines; the vendor's figure sequence exists to prevent exactly this.
The torque-wrench-on-the-press confusion. The forums keep asking whether the press stage needs the wrench set to something. It does not — the press is ratchet-to-a-stop on the old bolt; the wrench first appears at 75 ft-lb on the new one. Using a clicker as a press risks both the instrument and the angle of the hub.
The tensioner-tool number. Vendor sheet 3 Nm versus factory 0.6 Nm — both numbers are in print; know which one your kit intends and why before you lean on the tool. Either way the failure mode of too much is broken chain guides.
S55 breakaway reality. Over 600 Nm per the factory document. Two people and a pipe extension on the breaker bar is a documented method, not a joke.

The verify checklist

Hub face flush against the crank nose — no proud edge, inspected at the perimeter.
Fresh bolt, 75 ft-lb confirmed, full angle turned and tracked by the paint mark.
Timing verified the long way: rotated two full turns in the running direction, tools back on, TDC and cam locks re-seat without force.
VANOS bolts new, at 20 Nm + 180°.
Capture fitted, bolts at 40 ft-lb, no forcing of the clocking.
All one-time hardware renewed — pan, damper, VANOS, tensioner sealing rings.
Oil system primed and coolant bled per the refresh sequence before first start.

Sequencing with the rest of the front-end job

The install rides the chain-job access the engine pages describe — damper, seal, chain, tensioner. While the front is apart: chain guides and tensioner per the valvetrain and timing refresh judgment, the front crank seal (step 6), and if the head is coming off for gasket or stud work, the HCR head stud guide sequences that adjacent job. A car that needs both belongs on one parts order and one plan, not two openings of the same front end.

Where the factory numbers live

The engine pages carry the full factory procedures this install assumes — tools, torque tables, and the honest step summaries: N54, N55, S55, and the overview for the field map. The conversions guide owns the decision layer. Every factory number on this page traces to the factory document ids listed in the sources; every kit number is the vendor's, from their install guide current as of October 2026 — verify against the sheet in your box.

References — the research shelf

Factory sources

Questions

Is the crank bolt capture really required with a splined hub?

Treat it as required. The vendor's own install sequence ends with the capture going onto the damper, their materials state the splined hub is not intended to run without one, and the reason is mechanical: the splines stop the hub from slipping, but the bolt can still back off and unload the joint. In the install guide's packing list the capture appears as an optional line item only because the kit sells in several configurations — budget for the pair and you will not be surprised.

How do I know the hub is fully seated?

The press stage has no torque number — the vendor's instruction is to tighten the old bolt with a half-inch ratchet until it stops, then confirm the hub is pressed all the way in. In practice: the hub face sits flush against the crank nose with no visible gap at the perimeter, the ratchet stops taking movement, and the subsequent 75 ft-lb stage on the new bolt moves the bolt, not the hub. If the hub still stands proud of the nose, the press is not finished.

Can I install a splined hub with the oil pan still on?

The vendor says it is possible but very difficult and not recommended — their suggestion is to remove the pan for the job. Nothing in a splined install requires pan-off access for drilling (there is no drilling), so this is purely an access and insurance call, unlike the pinned conversion where the pan comes off for chip control.

Can a splined hub go onto a crank that already slipped?

Only if the nose survived. The vendor's guide is explicit: degrease the crank snout and check for burrs or damage from a previous slip, because the crank has to be in good shape to accept the splines. A scored or burred nose means the broached joint will not be uniform — that crank needs inspection, and probably a different conversation, before any hub goes on.

Do I need a torque wrench for the press stage?

No — and you should not use one for it. The press is an uncontrolled 'tighten until it stops' operation on the old bolt with a ratchet; a clicker torque wrench is a measuring instrument, not a press, and this stage routinely exceeds what it should feel. The torque wrench enters the job afterwards, for the 75 ft-lb stage on the new bolt.