Drive belt sizing

[Notthenow]

I need some advice on an obscure issue. I have changed the pulley sizes and amount of items being driven. It's easy to measure the overall size, BUT how much SMALLER should the belt actually be for proper tension using the stock idler tensioner?

 

[ttocs]

I grabbed a buddy put the ratchet in the tensioner and had them push it down while you use some wire/string to measure it while its short

 

[Notthenow]

Good idea, what I don't remember is how close to minimum is it. Splitting hairs, but I don't want it to squeal or be too tight on the bearings.

 

[tvsn95]

Hands down the best way to do this is get an old belt that is too long , cut it. then wrap it around the way you want with the tensioner in full compression. then measure to within 1/2 inch ( in inches) write it down. then go study the belts at the auto store. you will see that the numbers start to make sense. always get the tightest fitting one. DONE

 

[Notthenow]

Thanks, I found AC Delco always lists the size of the belt in part detail. Their part number then includes the size in inches. Im my case I ended up needing a belt 2 inches shorter. Delco had one and the local parts store cross referenced to Gates. As both you and toccs indicated, go with the smallest that fits with the tensioner fully in.