Envelope, load and speed: choosing a series for a given shaft diameter
2026-09-16
A real comparison at 25 mm bore across 6000/6200/6300 and the thin-section series (6800/6900/16000) — plus why Cr and C0r are not "permissible loads".
You know the shaft diameter is 25 mm. Which series comes next? Rather than rules of thumb, here is the comparison using the actual figures in our parameter table.
First: are you making something new, or replacing a bearing?
- New design — the housing dimensions are yours to decide, so you can trade freely between series (a bigger series for more load, a thin-section series to save space).
- Replacement — you must verify the mounting dimensions first: outer diameter D, width B, and the corner/shoulder requirements. Do not swap across series just because the bore matches (as the table below shows, the same bore can come with quite different outer diameters).
⚠️ The comparison here applies to choosing a series in a new design. If you are replacing an existing bearing, send us the original model number so we can check the dimensions.
25 mm bore: six series, actual figures (all open type)
| Series | Model | Outer diameter D | Width B | Dynamic rating Cr | Static rating C0r | Grease limiting speed |
|---|---|---|---|---|---|---|
| 6800 (thin) | 6805open | 37 mm | 7 mm | 3.66 kN | 2.65 kN | 18,000 rpm |
| 6900 (thin) | 6905open | 42 mm | 9 mm | 7.0 kN | 4.55 kN | 16,000 rpm |
| 16000 (thin) | 16005open | 47 mm | 8 mm | 7.3 kN | 4.95 kN | 15,000 rpm |
| 6000 | 6005open | 47 mm | 12 mm | 10.1 kN | 5.8 kN | 15,000 rpm |
| 6200 | 6205open | 52 mm | 15 mm | 14 kN | 7.9 kN | 13,000 rpm |
| 6300 | 6305open | 62 mm | 17 mm | 22.45 kN | 11.55 kN | 11,000 rpm |
(Figures are comparable only at the same bore and the same seal configuration — here all are open.)
Two trade-offs you can read straight off the table
- The larger the series, the more space it takes, the more load it carries, and the lower its limiting speed.
6000 → 6200 → 6300: outer diameter 47 → 52 → 62 mm, Cr 10.1 → 14 → 22.45 kN, while the grease limiting speed falls 15,000 → 13,000 → 11,000 rpm. Two sides of the same coin.
- The thin-section series (6800/6900/16000) save the most space at a given bore — but carry the least load.
6805 is only 37 mm in outer diameter, but its Cr is just 3.66 kN. ⚠️ On speed, "thin section = fastest" does not hold in general: in this table the 6800 series is fastest (18,000 rpm), yet 16005 and 6005 both reach 15,000 rpm — read the speed of the specific model, not the series.
❗Two things that are easy to get wrong
① Cr and C0r are not "permissible loads" — and they do not mean you may overload the bearing. They are the basic dynamic and basic static load ratings: calculation references for rating life and static safety checks.
⚠️ Do not read this as "if the load stays under C0r it is safe." A real selection must be checked against the peak equivalent static load P0 and meet the required safety factor s0 = C0r / P0 — especially for slow-running or stationary duty. What an application can carry depends on the nature of the load, the equivalent dynamic load, the safety factor and the real operating conditions.
② A higher Cr does not guarantee a longer service life. At the same equivalent dynamic load, a higher Cr means a longer calculated rating life; it does not guarantee that the bearing lasts longer in practice — that also depends on mounting, lubrication, clearance, contamination and temperature.
Our position: the parameter table provides calculation references, not a commitment about actual service life.
Why replacements always need a dimension check
At the same bore, two models can share an outer diameter but differ in width:
- `16005open`: 25 mm bore, 47 mm outer diameter, 8 mm width
- `6005open`: 25 mm bore, 47 mm outer diameter, 12 mm width
Same outer diameter, 4 mm difference in width. The two are not directly interchangeable: the narrower one may physically fit the same housing, but its axial location and load position differ, so it may not suit the original arrangement. (This table compares figures, not interchangeability — for a replacement, send us the original model and we will check.)
A sensible order for narrowing down a series
- Envelope — housing bore and available width; rule out the impossible series first
- Load — predominantly radial, or is there axial load as well
- Static check — for shock or heavy static duty, check against C0r
- Target life — calculate the rating life from the equivalent dynamic load and Cr against your replacement interval.
Two cautions: the rating life L10 corresponds to 90% reliability (it is not a guarantee of that service duration); and converting it into hours requires the operating speed, so the answer changes with speed.
- Speed and lubrication — confirm your operating speed stays within the limit for the chosen model and lubrication method.
Again: the permissible speed also depends on temperature rise, load and lubrication condition — the tabulated figure is a threshold, not a guarantee (seal type affects it too).
Steps 3–5 are normally iterative: change the series and both life and speed change, so the checks have to be run again.
- Finally — send us the application and have our engineers confirm it
To narrow it down yourself first, use the bearing selector — it screens on each model's own figures — or send us the shaft diameter, envelope, speed and environment and our engineers will shortlist and confirm.