What is a Ribbed Belt and How to Select It?
Working principle of ribbed (Poly-V) belts, PH, PJ, PK, PL, PM profile types, and basic measurement steps for proper belt selection.
Last updated: 6 November 2026
A ribbed belt (also known as a multi-ribbed or Poly-V belt) is a power transmission element that combines the flexibility of flat belts with the high power transmission capacity of V-belts. The inner surface of the belt features multiple longitudinal V-shaped ribs. This structure increases the contact surface area between the pulley and the belt, allowing high torque transmission through friction.
Advantages and Applications of Ribbed Belts
Because it has a thinner cross-section compared to standard V-belts, it can operate on small-diameter pulleys without bending difficulties. It is suitable for serpentine drives where multiple pulleys are driven by a single belt.
Main areas of use include:
- Automotive auxiliary drive systems (alternator, air conditioning compressor)
- Home appliances (washing machines and dryers)
- Industrial fans, pumps, and compressors
- Fitness equipment and agricultural machinery
Ribbed Belt Profiles
Ribbed belts are classified according to the distance between the ribs (pitch) and the rib height. The most common standard profiles in the industry are:
| Profile | Rib Pitch (Approx.) | Typical Application |
|---|---|---|
| PH | 1.60 mm | Small appliances, light devices |
| PJ | 2.34 mm | Washing machines, small power tools |
| PK | 3.56 mm | Automotive engines, medium-scale machinery |
| PL | 4.70 mm | Industrial compressors, heavy-duty fans |
| PM | 9.40 mm | Heavy industrial machinery, crushers |
For detailed information on the sequence of letters and numbers on the belt, you can check our guide on how to read belt codes.
How to Select the Right Ribbed Belt?
Follow these four steps when replacing a belt in an existing system or requesting a new part:
- Determine the Number of Ribs: Count the peaks (ribs) across the inner surface of the belt. For example, if there are 6 peaks, the belt has 6 ribs (such as 6PK).
- Identify the Profile Type: Measure the distance between the tips of two adjacent ribs with a caliper and verify the profile letter (PJ, PK, etc.) from the table above.
- Measure the Length: If the code on the old belt is worn off, measure the outer circumference of the belt with a tape measure. In ribbed belts, the number in the code generally indicates the effective length in millimeters.
- Check for Elasticity: Some applications do not have a tensioner pulley and use elastic belts (coded
EL,EPJ, orMAEL). Standard belts cannot be installed in these systems; always specify whether the belt is elastic when ordering.
You can search for the product whose dimensions you have determined using our belt and seal finder tool or browse our products page. For special dimensions, you can reach us via the quote page.