A pump rebuilder in the Netherlands ordered 600 pieces of 6211 2RS bearing for irrigation pumps and took the cheapest quote. The parts arrived dead on size, 55x100x21, sealed and pre-greased. Three months later the pumps ran hot and two seized. The rating he sized them on came off one brand's catalogue, and the brand that shipped was rated 20% lower. That gap is the whole story.
The 55x100x21 Numbers
The 6211 2RS bearing measures 55 mm bore, 100 mm outside diameter, 21 mm width and a 1.5 mm chamfer. Those numbers come from ISO 15 and do not move between brands, which is why the part is a true drop-in even when the performance is not. The full envelope table is on our ISO standard ball bearing sizes page.
What buyers underestimate is where 6211 sits. It is the medium section of the 6200 series, and a 55 mm shaft gives you four real options. The 16011 carries about 19 kN, the 6011 around 28 kN, the 6211 above them, and the 6311 roughly 72 kN at 55x120x29. Same shaft, four different machines. A 6211 2RS bearing weighs about 0.61 kg against 1.34 kg for the 6311, so 600 pieces of the heavier frame adds 440 kg of freight. The rest of the family sits on the 6200 series deep groove ball bearings page.
Load Ratings: Cr Moves By 25%, C0r Does Not
Here is the number nobody checks when they buy a 6211 2RS bearing. Six public catalogues give the basic dynamic load rating Cr as 43.4, 43.4, 43.5, 46.0, 46.2 and 54.2 kN. Same part number, same envelope, a 25% spread. The static rating C0r tells the opposite story: all six sit between 29.0 and 29.4 kN.
A distributor in northern Germany found this on 2,000 pieces for a conveyor gearbox. He compared three quotes on price and Cr, took the lowest, and shipped parts rated 43.4 kN into a duty his own calculation had sized at 46 kN. They failed at fourteen months instead of the four years his maintenance plan assumed.
Cr is not a peak load you may touch occasionally. It is the load that gives a reference life of one million revolutions, so real selection derates it. Get the Cr from the maker's own datasheet. If 43 kN covers your duty, a 43.4 kN part is honest; if you are sizing off 54 kN, put that in writing.
What The 2RS Seal Costs You In Speed And Heat
2RS means two rubber contact seals, normally NBR, factory-greased and maintenance-free once fitted. The lip seals against the inner ring, which is why the bearing arrives pre-packed. That same lip is what you pay for in speed: inside one maker's own table, their open 6012 is rated 6,700 rpm on grease and their 6012 2RS only 4,300.
On a 6211 2RS bearing the figures are just as scattered, with 2,400, 3,900, 4,100 and 4,300 rpm all quoted for the same sealed envelope and one oil figure at 10,000 rpm. Read that as a reference, not a ceiling. Temperature is the other edge: NBR seals are usually rated to about 100 C, so a hot application moves to FKM fluoro-rubber at roughly 150 C or drops the seal.
A Turkish textile plant ran 6211 2RS bearing on felt rollers at 3,200 rpm in a room near 70 C. The bearings survived; the grease did not. The fill broke down by month five and eleven units seized. Higher temperature grease and better ventilation fixed it cheaply.
Brand Interchange: 2RS1, 2RSR, DDU, And LLU
Every major brand writes the sealed 6211 2RS bearing differently. SKF uses 6211-2RS1, FAG and Schaeffler 6211-2RSR, NSK 6211DDU, NTN 6211LLU, and Koyo and Timken both write 6211 2RS. All six are the same 55x100x21 envelope with a contact seal on both sides.
Dimensional interchange is not performance interchange. Clearance runs from C2 to C5, with CN normal and C3 the common motor choice, and precision runs from normal PN up to P6 and P5. Those letters decide whether a hot gearbox runs free or pinches its own balls. The deep groove ball bearing suffix guide breaks down what each one changes.
A maintenance planner at a South African mine cross-referenced a hot gearbox from an SKF 6211-2RS1 in C3 to a generic 6211 2RS bearing in CN. He fitted twenty before anyone noticed. The bearings ran tight, the outer rings crept in their housings, and the gearbox came apart twice.
Fitting It: Shoulders, Fits, And The Mistake That Costs Most
The seating numbers for a 6211 2RS bearing are tight. Shaft shoulder diameter runs from 64 mm to 69 mm, housing shoulder to 91 mm maximum, and the shaft fillet must stay inside 1.5 mm. Motor duty figures put the journal at 55.01 mm maximum in a k5 fit and the housing bore at 100 mm in H6.
The mistake that costs the most is pressing on the wrong ring. On a rotating shaft the interference is on the inner ring, so push there. Push on the outer ring instead and the load path runs through the balls and leaves brinelling behind. A gearbox rebuilder in Izmir pressed 150 6211 2RS bearing onto shafts through the outer ring because it was the flatter surface. Forty of the 150 were noisy on the bench, and the claim cost more than the gearboxes. A fitting tube that contacts only the inner ring ends that failure for less than one bearing.
Quick Answers Before You Order
Is a 6211 2RS bearing the same as a 6211-2RS1? Dimensionally yes, both are 55x100x21 with contact seals. The suffix systems differ by brand, so confirm clearance and precision on the datasheet.
What is the basic dynamic load rating? Between 43.4 and 54.2 kN across the catalogues we compared, with a static rating near 29 kN. Ask for the figure from the maker who will ship.
What speed does it run? Published grease figures for the sealed version run from 2,400 to 4,300 rpm. Use that maker's own table and derate it.
Can a 6011 or a 6311 replace a 6211 2RS bearing? The bore matches; the envelope and the load do not.
The 6211 2RS bearing is fixed at 55x100x21, but its Cr, its clearance, its precision and its seal material are choices, and the catalogue that quoted the number is part of the specification. Send your duty, shaft size and quantity through our contact page and we will come back with the Cr, clearance and seal that fit the machine rather than the cheapest line on the sheet.
