Timing Belts – Procedure for Belt Identification
Step 2 - What is the material of the belt? Rubber or plastic?

Common timing belts are made of two different materials...

... rubber = black, ordinarily of fibreglass...

... and polyurethan = light plastic, ordinarily of steel fibre.
Step 3 - What is the belt type and pitch?

Rubber belts with rounded teeth (HTD), measurements are generally given in mm...

... whereas with squared teeth, measurements are given in inches...

... and less common, there are belts with a rounded tooth with a flat top – STD (upper belt).

Pitch is measured from the right edge to the right edge of two adjacent teeth, e.g. 9.53 mm = 3/8 in (belt type L)…

... or from the centerlines of two adjacent teeth, e.g. HTD pitch = 8 mm...

... or plastic belt pitch is 10 mm.
The most common belt types according to pitch:
- HTD 03M, 05M, 8M, 14M
- STD S03M, S05M, S08M, S14M
- Inches MXL, XL, L, H, XH, XXH
- Polyurethane T and AT
Step 4 - What is the length? Belt length = number of teeth?

DO NOT MEASURE the length of the belt with a cord, this is INACCURATE!

The surest method is to count the teeth.

Mark the tooth where you begin counting...

... preferably, mark every 10th tooth thereafter.

Belt length = no. of teeth x belt pitch.
Step 5 - What is the belt length?

Measure the width of the belt, e.g. 16 mm…

... or measure the belt in inches, e.g. 19.05 mm = 3/4 in, i.e. belt type 075.
More tips for belts identification

Newer belts have markings identifying product number and manufacturer...

... aiding you in determining the right belt type...

... or allowing our technicians an easy identification.

For manufacturing reasons, width is not usually marked on newer belts and it is necessary to measure it before ordering!

Note the difference between belt types T and AT.

T teeth fit together...

... whereas AT teeth do not.

Special belts can have a Kevlar fibre reinforcement, as shown here in this belt cord.

Timing belts for garden machinery (often double-sided) are typically STD…

.... belts with a rounded tooth with a flat top – STD (upper belt).
In case of repeated belt damage or breakage, it is necessary to remove the belt and determine its fault.
Downloads:
- TYMA belts, a complete catalogue (pdf, 6 786 kB)
