27-06-2023

How do I measure a v-belt?

Drive Technology

Is your v-belt due for replacement and you don't know what size you need? In this blog we would like to explain to you how to measure a v-belt yourself. We can also always help you with this at our store.

What is a v-belt?
A v-belt, also called a v-belt, is a type of drive belt used to connect and drive two pulleys. When one pulley rotates, the v-belt causes the other to rotate with it. The v-shaped profile of the belt (hence the name) allows the belt to have more grip on the pulley, thus maintaining belt tension.

Sizes of a v-belt
There are different types of v-belts used in the industry. The width sizes are standardized by series, these are:

SPZ/Z = 10 mm
SPA/A = 13 mm
SPB/B = 17 mm
SPC/C = 22 mm

There are also important lengths to measure with a v-belt. These are the Li (internal length), Ld (guideline length/stitch length), La (external length) and Lw (working length). The internal length (Li) was used on older belts that were flat. As an example, a classic belt may read 10 x 800Li . This means it has a width of 10 mm (type SPZ/Z) and an internal length of 800 mm.

Measuring a v-belt

Today, the guide length (Ld) is used to determine the length of a v-string. This can be noted on a string as e.g. Z610. If this is not legible on a string, you can measure the length yourself. Use a tape measure (or a cord) and place it tightly along the inside of the v-belt; this is the internal length. For the external length (La) you do the same, but along the outside of the string. Is the v-belt snapped? Then you can easily measure the working length (Lw). Stretch the string all the way out and measure the total length of the v-belt, you will have the active length, which is equal to the guide length.

You can also calculate the guide length yourself with the following arithmetic: internal length + 22 mm(differs per string, see table). For this you first need to know the internal length (Li). Place a measuring tape tightly along the inside of the v-belt, this is the internal length (e.g. 585 mm). Apply then apply the arithmetic; 585 + 22 mm = 610 mm. So the guide length (Ld) is 610 mm, then you arrive at the 10X585LI Z610.

Classic profile

	Z/ZX	A/AX	B/BX	C/CX	D	E
La (external length)	Ld + 15	Ld + 20	Ld + 24	Ld + 29	Ld + 43	Ld + 58
La (external length)	Li + 38	Li + 50	Li + 69	Li + 88	Li + 119	Li + 151
Ld (guideline length)	Li + 23	Li + 30	Li + 45	Li + 59	Li + 76	Li + 93
Ld (guideline length)	La - 15	La - 20	La - 24	La - 29	La - 43	La - 58

Narrow Profile

	SPZ/XPZ	SPA/XPA	SPB/XPB	SPC/XPC
La (external length)	Ld + 12	Ld + 17	Ld + 22	Ld + 29
La (external length)	Li + 50	Li + 63	Li + 82	Li + 113
Ld (guideline length)	Li + 38	Li + 46	Li + 60	Li + 84
Ld (guideline length	La - 50	La - 63	La - 82	La - 113

Do you need help measuring your v-belt? Then contact us, we will be happy to help you determine the right type of v-belt.