Fan belts

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by: Cobalt327
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Belt sizing is fairly simple, you don't need to know the part number for the size belt you need, you just need to figure out how the part number is made up, as it is made up of the belt width, and the circumference of the belt. with Gates V belts it's pretty simple to figure out as the information is easy to read out of the part numbers.

I'll only explain Gates belts, there the most common belts used and there # cross reference to other company's anyway

You have the belt width, it is in a code but simple to follow, as it's only 2 numbers

67= 3/8" width

68= 1/2" width

69= 5/8" width

Now that you have the width you need, you just need the length which is easy it's the actual measurement in inches with one decimal place, in HALF INCH INCREMENTS only. The decimal is omitted for the part number

So for example a 50" long 5/8" belt might be needed, so you order a 6950 belt. A 5/8" belt 50 1/2" inches long would be a 6955

just to make sure that length is available go to and search the part number

  • A fairly straightforward way to come up with a custom sized belt is to get a new or used belt that is like what you need but much longer. Cut it. Route it as you need it with and tensioning device fully slackened. Then clamp the belt ends tight to each other with locking pliers. Then tighten the belt about halfway. When you are satisfied you then have a sample belt which your local parts counter person will find amusing but will most likely be able to match up. The reason to tighten your sample belt halfway is that the match won't be exact, the new belt will almost always be a bit longer or shorter. Setting your sample size at midpoint gives you some leeway. This also works with serpentine belts. They are easier to clamp tightly with the pliers than V-belts. But many serpentine setups have spring loaded tensioners which make it difficult to pinpoint the midway sizing. Such estimated on serpentine setups to err towards too long so it seems to be best to look for a new belt a bit shorter than your setup belt. A really good way to get such sizing right the first time only works if you have a very cooperative parts person. Such a person might allow you to purchase the closest matching belts and later return the one(s) you didn't need. Most parts stores keep a good selection of belts on hand, but they don't have EVERY belt available. They may not have one quite close enough for what you need. But they should be able to look one up and order it for you.
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