A V belt is an endless belt with a roughly trapezoidal cross-section that runs in a matching groove on the pulley. It wedges into that groove as the load rises, so it grips well with less width and tension than a flat belt.
This page covers the main V belt types, size codes, and how to pick one for a drive. Keep the code if it is still printed on your belt; if it is not, measure the section before you order.
Key Takeaways
- A V-belt sits in a matching groove and wedges in harder as the load rises.
- The main types are classical, narrow, cogged, banded, variable speed, hexagonal, light-duty and link V-belts.
- A size code is a letter plus a length number, and the same letter can mean different sizes in the metric and inch systems.
- Choose from power and speed ratio, shaft distance, drive unit, environment, load and pulley layout.
- Belt drives are efficient (90–98%, usually 95%) but transmit less power than gears or chain drives.
Table of Contents
- What is a V belt?
- Anatomy of a V belt
- Types of V belts
- V belt sizes and codes
- How to choose a V belt
- Advantages and limits of V belts
- Where V belts are used
- FAQ
- About Longyi Rubber Products Factory
What is a V belt?
A V belt has a roughly trapezoidal cross-section, which gives it the name. The V shape tracks in a mating groove in the pulley (the sheave), so the belt cannot slip off. It also wedges into the groove as the load increases: the greater the load, the greater the wedging action. That is why a V-belt needs less width and tension than a flat belt, and why V-belts have mainly replaced flat belts for short-distance power transmission (Belt (mechanical) on Wikipedia).
For higher power, two or more V-belts run side by side on matching multi-groove sheaves, an arrangement called a multiple-V-belt drive. Some V-belts are one material throughout, while others carry reinforcing fibers: cotton, polyamide or polyester or, for greatest strength, steel or aramid (Belt (mechanical) on Wikipedia).
Anatomy of a V belt
An endless V belt is a closed loop with three working parts: a cover or outer layer, a tension section of cord that carries the pull between the sheaves, and a rubber body that wedges into the groove.
The cover can be wrapped (fabric-covered) or raw-edge (cut flanks with no fabric jacket). The section letter does not tell you which build you have, so look at the flanks. The article on wrapped and raw-edge belts explains when each is used.
Types of V belts
| V-belt type | Construction | Where it fits |
|---|---|---|
| Classical (Z, A, B, C, D, E) | Trapezoidal belt in the older, wider section family | General industrial drives; see the size tables for dimensions. |
| Narrow (SPZ, SPA, SPB, SPC, 3V, 5V, 8V) | Deeper section for its width | Compact drives on the narrow-section pulleys. |
| Cogged (notched) | Notches molded into the underside | Drives with small pulleys where the belt has to bend more. |
| Banded | Several belts joined by a tie band | Multi-groove drives that see pulsating loads. |
| Variable speed | Wide top width for adjustable-pitch pulleys | Drives where the speed is changed by moving the pulley flanges. |
| Hexagonal | Grooves on both faces | Drives that need to be driven from both sides. |
| Light duty | Small fractional-horsepower sections | Small machines and appliances. |
| Link V-belt | Composite links joined together | Fitting a belt where an endless one will not go on; length changes by adding or removing links. |
Link V-belt description: Belt (mechanical) on Wikipedia. Other rows describe the construction names used in belt catalogs.
Match the row to the belt you are replacing, then check the groove.
The classical family (Z, A, B, C, D and E) is the older, wider section; the narrow family is deeper for its width and is used on compact drives with pulleys cut for it. Inch narrow codes are 3V, 5V and 8V, and metric narrow codes are SPZ, SPA, SPB and SPC. The industrial range lists classic V-belts and narrow V-belts separately.
A cogged belt has notches molded into the underside, which suits drives where the belt has to bend more around small pulleys; see cogged V-belts. A banded belt joins several belts with a tie band for multi-groove drives, and a hexagonal belt has a V profile on both faces so it can be driven from either side.
A variable speed belt has a wide top for adjustable-pitch pulleys, where the speed changes as the pulley flanges move. Light duty (fractional horsepower) belts use 3L, 4L and 5L sections, with nominal top width and height of 3/8 × 7/32 in, 1/2 × 5/16 in and 21/32 × 3/8 in (Turn2Engineering V-belt size chart).
When an endless belt does not fit, jointed and link V-belts may be used. A link V-belt is made of composite links and is length-adjustable by removing links (Belt (mechanical) on Wikipedia). Removing a link changes the length, not the section, so the groove still has to match.
V belt sizes and codes
A size code puts a letter and a number together. The letter names the cross-section and the number gives the length, but the length is measured on different bases: A100 is 100 in of inside circumference, while 5V750 is 75.0 in of outside circumference (Turn2Engineering V-belt size chart).
The letter also means different things in the metric and inch systems. An unqualified A or B is ambiguous across systems, and a dimensional match does not establish interchangeability, the correct length, the pulley groove or duty (Turn2Engineering V-belt size chart).
ISO/DIN classical nominal top width and height are Z 10 × 6 mm, A 13 × 8 mm, B 17 × 11 mm, C 22 × 14 mm, D 32 × 20 mm and E 38 × 23 mm (Turn2Engineering V-belt size chart).
| Section (ISO/DIN metric) | Top width × height (mm) | Top width × height (in, converted) |
|---|---|---|
| Z | 10 × 6 | 0.39 × 0.24 |
| A | 13 × 8 | 0.51 × 0.31 |
| B | 17 × 11 | 0.67 × 0.43 |
| C | 22 × 14 | 0.87 × 0.55 |
| D | 32 × 20 | 1.26 × 0.79 |
| E | 38 × 23 | 1.50 × 0.91 |
Dimensions: catalog nominal values as compiled in the Turn2Engineering V-belt size chart. Inch values in the first table are converted at 25.4 mm per inch.
The US narrow sizes are 3V at 3/8 × 21/64 in, 5V at 5/8 × 35/64 in and 8V at 1 × 7/8 in (Turn2Engineering V-belt size chart).
| Section | Top width × height (in) | Top width × height (mm) | Length basis of the code |
|---|---|---|---|
| 3V | 3/8 × 21/64 | 9.5 × 8.3 | Outside length in tenths of an inch |
| 5V | 5/8 × 35/64 | 15.9 × 13.9 | Outside length in tenths of an inch |
| 8V | 1 × 7/8 | 25.4 × 22.2 | Outside length in tenths of an inch |
Dimensions: catalog nominal values as compiled in the Turn2Engineering V-belt size chart. Inch values in the first table are converted at 25.4 mm per inch.
Match the section and the length on the V belt size chart. If you know the pulley diameters and the center distance, the V-belt length calculation gives the length, which you then check against the groove.
How to choose a V belt
Choose a V belt from the drive, not from a letter you remember. Write down these six facts before you name a section:
- The power the drive must transmit and the speed ratio between the pulleys.
- The shaft distance, and whether the center distance is long or short.
- The drive unit, such as an electric motor or an internal combustion engine.
- The service environment: oily, wet or dusty conditions, and the heat around the belt.
- The load: steady, jerky, shock or reversed.
- The pulley arrangement: open, crossed or turned, and how many sheaves the belt touches.
Then check the pulleys. Keep the center distance larger than the bigger pulley diameter but less than three times the sum of both pulleys. The optimal belt speed range is 1,000–7,000 ft/min (300–2,130 m/min) (Belt (mechanical) on Wikipedia).
Small pulleys greatly reduce belt life, and two or more V-belts side by side are often more economical than one larger belt (Belt (mechanical) on Wikipedia).
Advantages and limits of V belts
Belt drives run smoothly and with little noise, provide shock absorption, and help protect machinery from overload and jam. Their efficiency is 90–98%, usually 95%, and working temperatures range from −35 to 85 °C (−31 to 185 °F) (Belt (mechanical) on Wikipedia).
Belt drives transmit less power than gears or chain drives. Slip and stretch mean the speed ratio is not exactly fixed, and the center distance has to be adjustable, or an idler added, to compensate for wear and stretch (Belt (mechanical) on Wikipedia). If slip is not acceptable, a timing belt is the usual answer: its teeth fit a toothed pulley, and when correctly tensioned it has no slippage.
Where V belts are used
V belts drive compressors and other industrial machinery, farm machinery and automotive accessory drives. The V shape is shared, but the section and length still have to match the machine.
The industrial range includes classic V, narrow V, cogged V, banded V, banded cogged narrow, hexagonal, variable speed, light duty and raw-edge belts, plus industrial multi-ribbed belts and timing belts; see the industrial belt range. OEM and ODM V belts are built to the customer’s part number, drawing or size, with private label and packaging (OEM and ODM page). Send the belt code or a photo of the belt.
FAQ
Why is it called a V belt?
Because its cross-section is a wedge shaped like a V, which sits in a matching pulley groove (Belt (mechanical) on Wikipedia).
How do I find the size of a V belt?
Read the whole code on the belt. If it is gone, measure the top width and height and compare them with the V belt size chart, then check the length basis and the pulley groove.
Can I replace a classical V belt with a narrow one?
Not reliably. A similar measurement does not prove the belt will interchange, so check the full code and the pulley groove (Turn2Engineering V-belt size chart).
What is the difference between a banded belt and a multiple-V-belt drive?
A multiple-V-belt drive runs two or more separate V-belts side by side on matching multi-groove sheaves (Belt (mechanical) on Wikipedia). A banded belt joins those strands with a tie band into one belt.
What is a link V belt?
A V-belt made of composite links, used when an endless belt does not fit; its length is adjusted by removing links (Belt (mechanical) on Wikipedia).
Do you make V belts for OEM or private label?
Yes. OEM and ODM belts are made to the customer’s part number, drawing or size, and private label and packaging are available.
Sources
Source names appear here only as references. LYBELT is not affiliated with them.
About Longyi Rubber Products Factory
LYBELT is the brand of Longyao County Longyi Rubber Products Factory (General Partnership), based in Longyao County, Xingtai, Hebei, China, and making rubber belts since 1999. The factory holds IATF 16949 and ISO 9001 certification and works from 130+ rubber compounds.
The range covers automotive, industrial, agricultural, ATV/UTV and motorcycle belts. For OEM and ODM orders, belts are made to the customer’s part number, drawing or size, with private label and packaging. Email: luxin@lybelt.com.