What sets the limit?
Four things, and the lowest one wins.
- The grease (steel-on-steel). Traditional grease may break down at high temperature, and steel-on-steel bearings that need regreasing depend entirely on the thermal stability of the lubricant. One maker gives its lithium greases for steel/bronze bearings as −20 °C to +110 °C; ask the maker for the figure that goes with your steel/steel grease (Q1-08).
- The seal. One maker gives its seals −10 °F to +250 °F (about −23 °C to +121 °C) and says special seal materials are available beyond that (Q1-11).
- The liner (PTFE types). NHBB shows that different liner systems have different ranges, which it lists from −65 °F to 250 °F for some, to −65 °F to 400 °F for others, and 450 °F to 625 °F for its high-temperature liners for long-term use.
- The fit and the clearance. The same supplier's recommended fits are based on −65 °F to 350 °F, and at higher temperatures the different expansion of shaft, bearing and housing must be allowed for (Q1-06, Q1-07).
What ranges have makers published?
These are examples from different makers and designs. They are not interchangeable.
| Source | Type | Range |
|---|---|---|
| One supplier, "typical" | Steel/steel | −30 °C to +120 °C |
| The same supplier, "typical" | PTFE composite, maintenance-free | −40 °C to +180 °C |
| The same supplier | Specialised high-temperature | up to +200 °C |
| One maker | Its standard bearings, without restriction | −10 °C to +80 °C |
| One catalogue (its suffix C is PTFE fabric; suffixes differ by maker, see Q1-01) | Steel/PTFE fabric | −50 °C to +150 °C |
| An aerospace liner supplier | Aerospace liners; ranges by liner | −65 °F to 250 °F (−54 °C to 121 °C); −65 °F to 400 °F (−54 °C to 204 °C) |
| Same maker | Its AD, AK and K liners | long periods at 350 °F (177 °C), short periods up to 500 °F (260 °C) |
| Same maker | High-temperature (HT) liner | up to 625 °F (329 °C), qualified at a lower load than the AD/K liners |
For RS-sealed and roller-bearing types, one maker says to look in the type description. Industrial users rarely need the aerospace rows; they show how far a liner can be taken, not what a standard bearing does.
What happens outside the range?
Above the upper limit, material degradation can permanently damage the sliding surfaces, steel parts can lose hardness, and composite materials can break down or lose their self-lubricating property. In the cold, below −30 °C, materials must keep their dimensional stability, and PTFE composite types often do better than steel-on-steel types that may need special low-temperature lubricants.
Does the bearing's own heat count?
Yes. Higher loads create more friction and heat that can push the temperature past safe limits, and a higher movement frequency can raise the temperature too (Q1-04). The friction coefficient of PTFE also falls as load and temperature rise, and rises with surface speed and mating surface roughness.
What should you tell the maker?
The highest and lowest temperature at the bearing (not just the air), for how long, how often it changes, the load and the swing rate, and what lubricant or liner you plan to use.
Where does heat or cold come from on a vehicle pivot?
From things near the joint that the air temperature does not show: brake rotors and calipers, exhaust headers and turbo pipes, the engine bay, and desert sun on dark paint. A pivot can also heat-soak after the vehicle stops. What counts is the temperature at the bearing, so measure it after a real run with a contact probe or temperature-indicating paint rather than assume it.
Then apply the same rule as above: the lowest limit among grease, seal, liner and fit wins. Some vehicle-specific effects follow. Which ring runs hotter depends on where the heat arrives: heat conducted along a hot bolt or spindle warms the inner ring first, the case where a looser clearance group may be needed (Q1-07), while heat radiated onto the arm warms the housing first, and an aluminium arm loosens its fit as it warms (Q1-06). In the cold, grease stiffens and the first movements can stick and squeak (Q1-13). A heat shield or a different routing for the pipe can be a simpler fix than a different bearing.