Why Ball & Roller IMS Bearings Require Service Intervals

Summary: Rolling‑element IMS bearings are contact-type bearings. When factory grease seals are left in place, lubrication relies primarily on internal grease and incidental splash oiling. Even with seals removed and oil access improved, these bearings remain susceptible to contamination and fatigue, and they fail abruptly when they do fail—hence defined service intervals. In contrast, an oil‑fed plain bearing operates on a hydrodynamic film of filtered, pressurized oil and has no scheduled replacement interval.

1) Service Intervals (By Kit)

Recommended replacement intervals under normal service (time or miles, whichever comes first):

Kit / Bearing Type	Recommended Interval	Notes
Dual Row IMS Retrofit	6 years / 75,000 miles	Replace proactively; ideal timing is during clutch service when applicable.
Single Row Pro IMS Retrofit	6 years / 75,000 miles	Higher load capacity vs. original single row.
MY06–08 IMS Retrofit (serviceable conversion)	6 years / 75,000 miles	Converts the non‑serviceable factory arrangement to a serviceable solution.
RND RS Roller IMS Retrofit	6 years / 75,000 miles	Service interval applies; still a rolling‑element design.
Triple Row IMS Upgrade	6 years / 75,000 miles	Service interval applies; still a rolling‑element design.
Pelican PEL‑IMS‑1 (comparison)	3 years / 36,000 miles	Listed for customer reference.
IMS Solution (oil‑fed plain bearing)	No service interval	Pressure‑fed plain bearing—engine‑life system with routine oil service.

2) When the Bearing Is Already Failing

• Preventative vs. reactive: The IMS Retrofit and IMS Solution are preventative. If the factory bearing is already failing, an in‑car retrofit will not undo internal damage or contamination already present.
• Critical guidance: If the bearing has failed, do not attempt to install another bearing; the correct path is engine disassembly and replacement of not only the bearing but the whole intermediate shaft.

3) Grease Seal & Lubrication Facts

• All factory Porsche IMS bearings have grease seals. With seals left in place, the bearing relies primarily on its internal grease; engine oil cannot do its job.
• With the grease seal removed, any factory IMS bearing is submerged in engine oil. Removing the seal allows engine oil access for lubrication and contaminant purging.
• MY06–08 emphasis (non‑serviceable from factory): The larger 2006–08 bearing cannot be replaced in‑car. In practice, you can remove the grease seal, run a higher‑quality oil, and shorten oil change intervals. Full bearing replacement requires complete engine disassembly.

4) Direct Oil Feed (DOF) Guidance

• IMS Retrofit kits use open (unsealed) ceramic‑hybrid bearings designed to operate in engine oil.
• Do not pair IMS Retrofit kits with forced‑oiling add‑ons not engineered for them.
• For MY06–08 engines with the grease seal removed, a DOF is generally unnecessary because the bearing runs submerged in engine oil; focus on oil quality and maintenance intervals.

5) Pre‑Qualification Reminder

Before scheduling IMS work, pre‑qualify the engine. A meaningful percentage of engines do not pass initial checks and require repairs prior to proceeding.

6) Why Ball/Roller Bearings Need Service Intervals (Expanded)

• 24/7 preload: The IMS is under continuous load even when the engine is off. Three timing chains pull in different directions, held by pre‑loaded tensioners, which concentrates static load on one or two balls at rest.
• Worst‑case at low speed: Start‑up and shut‑down are high‑stress moments: speed (and EHL film thickness) is low while load is high, so mixed/boundary lubrication dominates and contact stress on balls and races spikes. This accelerates micropitting and spalling.
• Observed failure timing: Many rolling‑element IMS failures occur at start‑up or shut‑down rather than at steady operating speed.
• Other contributors: Limited or variable lubrication (especially with seals in place), contamination susceptibility, finite L10 fatigue life, and severe failure modes all necessitate defined mileage/time replacement intervals.
• Contrast to plain bearings: A pressure‑fed plain bearing (IMS Solution) maintains a hydrodynamic film with filtered, pressurized oil and therefore does not require a scheduled replacement interval—routine engine oil service governs longevity.