StarTech RKCASTER2 Replacement Server Rack Casters — Set of 4 (M6, 2-Inch, 45x75mm Bolt Pattern)
Overview
The StarTech RKCASTER2 is a set of four heavy-duty replacement casters designed to restore or upgrade the mobility of server racks and network enclosures that use an M6 bolt pattern measuring 45mm x 75mm. If your original casters have seized, cracked, or simply worn beyond safe use, swapping them for a verified replacement set is far preferable to working around a rack that can't be repositioned safely. Each caster uses a 2-inch (50mm) diameter wheel with a 1.7-inch (43mm) width, providing a stable footprint that resists tipping under load.
The full set ships at 5.2 lb (2.4 kg), and each caster body measures 3.6 in x 2.6 in x 2.9 in — compact enough to maintain the rack's original height profile and clear standard raised-floor tiles in most data center environments. If you're sourcing parts for a server rack accessory refresh, verifying your existing bolt spacing before ordering is the single most important step.
Key Features
- 551.2 lb (250 kg) Stationary Load Capacity: Each set of four supports a fully populated rack at rest — 551 lbs covers most 12U to 24U enclosures loaded with 1U servers, patch panels, and UPS units. If your rack is heavier than that statically, this replacement set is not the correct spec.
- 165.4 lb (75 kg) Rolling Load Capacity: Moving a loaded rack introduces dynamic stress that can exceed a caster's rolling rating well before its static limit. The 75 kg rolling capacity means you should depopulate heavier racks before repositioning — not an unusual precaution, but worth planning for in tight server rooms.
- 50mm x 43mm Wheel Geometry: The 2-inch wheel diameter keeps the rack height change minimal when swapping from worn originals, which matters if your rack has cable management arms or raised-floor cutouts calibrated to a specific clearance height.
- Steel and Rubber Construction: The steel frame handles the structural load while the rubber wheel surface protects raised-floor tiles, anti-static mats, and finished concrete from gouging or scuffing — relevant in any environment where floor surface integrity matters for static control or aesthetics.
- M6 Bolt Pattern (45mm x 75mm): This is the critical fit parameter. The 45mm x 75mm bolt spacing is common across several rack families, but it is not universal. Measure your existing caster mounting holes before ordering — a mismatched pattern means these won't mount without modification.
- Set of Four Included: All four casters ship together, so you're replacing the complete contact set rather than mixing worn and new wheels. Mixing caster ages creates uneven rolling resistance, which causes racks to drift or bind when moved.
Integration and Compatibility
The RKCASTER2 is compatible with server racks and open-frame or enclosed network cabinets that use an M6 threaded bolt pattern with a 45mm x 75mm hole spacing. This pattern appears on a range of mid-market and enterprise rack enclosures, though StarTech does not publish a universal rack compatibility list. The safest verification method is to remove one existing caster and measure the mounting plate directly. The casters are not specific to any brand of network rack enclosure — they are a mechanical fit based solely on the bolt pattern and thread spec.
For data centers running structured data center infrastructure where floor load ratings and mobility requirements are documented, confirm that your floor's point load spec accommodates the rack weight concentrated on four caster contact points. Raised-floor panels typically publish a rolling load rating that should be cross-referenced against the 75 kg dynamic capacity of these casters under load.
Frequently Asked Questions
Q: What bolt pattern does the RKCASTER2 use?
A: The RKCASTER2 uses an M6 bolt pattern with a hole spacing of 45mm x 75mm. Measure your existing caster mounting plate before ordering to confirm fit.
Q: What is the maximum load these casters can support?
A: The RKCASTER2 set supports a stationary load of 551.2 lb (250 kg) and a rolling load of 165.4 lb (75 kg). For heavier racks, depopulate equipment before repositioning to stay within the rolling capacity.
Q: How many casters are included in the RKCASTER2 package?
A: The RKCASTER2 includes a set of four casters — enough to replace the full contact set on a standard server rack.
Q: What is the wheel diameter on the RKCASTER2?
A: Each wheel is 50mm (approximately 2 inches) in diameter and 43mm (1.7 inches) wide, keeping rack height change minimal during a direct swap.
Q: What materials are the RKCASTER2 casters made from?
A: The casters use a steel frame with rubber wheels. The rubber wheel surface reduces floor damage on raised-floor tiles, anti-static mats, and finished concrete.
Q: Will the RKCASTER2 fit any server rack?
A: No. Fit depends entirely on the bolt pattern. The RKCASTER2 is designed for racks with an M6 thread and 45mm x 75mm hole spacing. Verify your rack's existing mounting geometry before purchasing.
The spec I always tell people to check first on the RKCASTER2 is the rolling load capacity — 165.4 lb (75 kg) for the full set. That number is easy to overlook when you're focused on the 551 lb static rating, but if someone tries to wheel a fully populated 24U rack across a data center floor without depopulating it first, you're going to exceed that dynamic limit and risk a caster failure mid-move. Knowing the difference between these two ratings before the move happens is what separates a clean migration from a dropped switch.
Technical Highlights:
- Static Load (551.2 lb / 250 kg): Sufficient for most mid-range rack deployments at rest — a fully populated 24U enclosure with 1U servers, a patch panel tier, and a small UPS typically lands in this range.
- 45mm x 75mm M6 Bolt Pattern: The fit parameter that determines everything. This is not a universal spec — it's specific enough that measuring your existing mounting holes is non-negotiable before ordering.
- Steel Frame + Rubber Wheel: Steel handles the structural load; rubber protects raised-floor tiles from point-load gouging. In environments with static-dissipative flooring, rubber wheels also avoid the scoring that bare metal wheels cause on coated surfaces.
Deployment Considerations:
- Before installing, confirm thread spec is M6 and hole centers match 45mm x 75mm exactly — a few millimeters of variance means the mounting bolts won't align, and forcing them damages the rack base plate.
- The 75 kg rolling capacity is the binding constraint in real deployments, not the 250 kg static figure. Plan rack moves with a partial depopulation if the loaded weight approaches or exceeds 165 lb.
The RKCASTER2 is the right call for IT teams managing a mid-size server room where racks need to be repositioned periodically for maintenance access or floor plan changes — specifically where the existing casters have failed and a like-for-like replacement on a 45x75mm bolt pattern is all that's needed to restore safe mobility.
