Home / News / Industry News / How to Measure V Belt And Its Tension

How to Measure V Belt And Its Tension


It is difficult for users to determine the length of th […]

It is difficult for users to determine the length of the V belt in your car. This holds especially true when measuring the length of a V belt running between two pulleys with different diameters and do not have experience using calibers to measure the diameter of the drive pulleys. Fortunately, you have an alternative to determine the length of a V belt accurately that does not require the use of a complicated mathematical formula or complicated measuring equipment.

Measuring Belt Length with an Old V Belt

You can use a white paint pen to do a mark on the side of an old V belt.

Set the flat outer edge of the V belt on a flat surface. Rotate the V belt to place the paint mark against the flat surface. Draw a mark on the flat surface with a pencil to designate the starting point of the measurement.

Roll the V belt along the flat surface until the paint mark rolls back to the flat surface. Place a second pencil mark on the flat surface to designate the contact point of the paint mark with the flat surface.

You should know the distance between the two marks for the circumference of the V belt.

Checking the tension of all your V-belts is also important. There are two measurements used in belt tension. Length of belt and amount of pressure for deflection. Knowing these measurements helps you setup and use your tension gauge.

Make sure the unit is turned off and the pulleys you are working with are not moving.

Check your V-belt to make sure whether it is cracked or worn in any spots. Look for any shiny parts along the part of the belt that comes in contact with the pulleys. This indicates belt slippage. You should change the damaged belts.

Measure the distance from the center of one pulley to the center of the second pulley. If there are more than two pulleys on the belt, take your measurement using the two pulleys with the longest span of the belt.

Multiply that measurement by one-sixty-fourth of an inch. If your belt is 16 inches, the equation is 1/64 x 16 = 16/64 or 1/4 of an inch. Set the "O" ring on the handle of your tension gauge to the measurement from your calculation. Set the second "O" ring on the plunger against the body of the tension gauge at the zero mark.

Place your piece of wood against the two pulleys, and line it up with the top edge of the pulley you are testing. Hold the wood in that position without moving it. Place the plunger end of the tension gauge on the top of the belt. Holding the tension gauge vertical to the belt press down until the bottom of the "O" ring on the plunger is even with the top of the wood.

Lift the plunger from the belt, and read the pounds of force measurement at the "O" ring on the plunger. This is the measurement that should match with the specifications listed in the manual for the device.

Replace the V belt as soon as possible if there is any type fo damage or excessive cracking anywhere on the belt.

Open the hood and turn the motor off and apply the parking brake.

Slide under the front end of the car and locate the engine cover between the radiator and the engine. Remove all of the bolts from the cover with the ratchet and a socket. Then, pull the cover down and slide it to the side.

Remove the air cleaner inlet tube from the air cleaner housing by unscrewing the band clamp with a flat head screwdriver. Pull the inlet tube off and set it to the side.

Locate the adjustment bolt on the top of the idler pulley. Loosen the adjustment bolt by turning it counter clockwise with the ratchet and socket. Once the belt is loose, remove it from the idler pulley and the other pulleys. Then, pull the belt out through the bottom of the engine compartment.

You can turn the adjustment bolt clockwise with the ratchet and socket to close the belt. Once the belt is tight, check the tension of the belt with your hand. If the belt has more than a half-inch of slack, then the belt is too loose. Continue to tighten the belt until there is a half-inch of slack in the belt.

Tighten the locking bolt in the center of the idler pulley tight with the ratchet and socket. Inspect the belt to ensure that is is properly seated inside of the each pulley. Then, crank the car and allow the motor to run for about twenty seconds Turn the motor off and recheck the tension on the belt with your hand.