FAQ Freewheels

The following section contains answers to frequently asked questions relating to freewheels.

If you have questions that are not answered here, feel free to send us an inquiry.




Installation instructions / usage instructions

1. The specified tolerance values (see DIN size tables) must be complied with.

2. The operating temperature must not fall below or exceed the permissible value.

3. Freewheel clutches without a seal must always be adequately lubricated.

4. Do not exceed torque peaks.

5. Do not exceed the permissible speed.

6. Freewheel clutches that are not already equipped with a bearing ex works require a bearing.

7. Freewheel clutches with a bearing must not be pressed in via the ball.

8. During use as a backstop, it may only be loosened when the system is at a standstill and load-free.

9. Observe the direction of rotation.

10. Installation may only be carried out by trained specialist personnel.

Please also observe the installation instructions/assembly instructions for the relevant series.

Our colleagues will be happy to help with any questions you may have.


What is the structure of a freewheel clutch?

What is the structure of a freewheel clutch?

In its basic form, a freewheel clutch is an assembly unit consisting of a defined number of clamping elements, a cage that distributes the sprags around the circumference and a spring that ensures constant friction contact between the clamping components and the connecting parts.

Combinations of these assembly units with rings, bearing and seals create different complete solutions.

What applications can freewheel clutches be used for?

Freewheel clutches can be used as overrunning clutches, backstops and indexing clutches.

What is the difference between the 2 spring systems?

Our insert elements are equipped with 2 different spring systems:

1. Meander spring, an elaborate individual springing of all clamping components;
2. Z spring, a simple tension spring that encompasses all of the sprags and provides them with a collective spring tension. The suffix “Z” must be specified as identification.

The following recommendation applies:

Indexing clutch = meander spring
Overrunning clutch = meander or Z spring
Backstop = Z spring


And what does the suffix "Z" mean?

Z spring (= tension spring), an annular spring that encompasses all of the sprags and provides them with a collective spring tension. The suffix “Z” must be specified as identification.

What stresses can a freewheel withstand?

The maximum permissible torque is determined by the size of the freewheel on the one hand and the wall thicknesses and strengths of the connecting parts on the other.

What must the connecting parts look like?

The requirements placed on the connecting parts are extremely different depending on the selected freewheel model. You can find an overview here:

Complete freewheel clutches
Ball bearing freewheel clutches
Freewheel clutch insert elements with rings
Freewheel clutch insert elements

What must be taken into account when selecting the lubricant?

Freewheel clutches can be lubricated with oil or grease.

With oil bath lubrication, it is sufficient for the freewheel clutch to stand up to 1/3 in the oil bath at a standstill.

For grease lubrication, it is important to ensure that the freewheel clutch is not excessively lubricated. Filling with grease completely can result in switching errors and overload the freewheel clutch.

Additives to reduce the friction value (e.g. MoS2) are not permitted.

You can find a selection of recommended and tested lubricants in our lubricant instructions.

Can the freewheel clutch be operated in very high / low temperatures?

Sealed freewheel clutches can be used up to 110 °C.
Max. 160 °C are permissible for open models.
The tempering temperature of 100 Cr 6 (sprags, rings, balls) is approx. 180 °C.

Caution is required for types with a plastic cage:
The FE 453 Z and FE 422 Z series and all complete freewheel clutch units containing these insert elements as components, as well as all ball bearing freewheel clutch units, have a plastic cage that can be used in up to max. 140 °C.

In very low temperatures, pay particular attention to the lubricant. Excessive grease quantities can lead to problems during “cold start” extremely quickly. As per FVA, indexing tests have been carried out at extremely low temperature of up to -40 °C and no major restrictions were identified.

Does a freewheel clutch require maintenance or re-lubrication?

The sealed models (62xx-2RS, FND, FPD, RA) are maintenance-free. For the others, the expected lubricant contamination must be estimated by the customer. The first lubrication/oiling is usually sufficient here. For installation in gears, the cyclical gear oil change is usually sufficient.

Can a freewheel clutch be switched off or switched?

No, a shutdown can only be carried out with a separate mechanical or electronic clutch coupling. A reversal of the power flow is not possible, GMN sprag type  freewheel clutches only work in one direction.

Are the RS seals used in the FK series leak-tight?

No! Thinner materials, e.g. water, watery emulsions, gasoline, light heating oil, solvents etc. seep under the seal; pressures can also not be sealed. The RS seal is designed for sealing against grease.