THE BIGGEST THING people do to hurt their external belts is over-tension them. There are two main types in use these days: a serpentine belt that looks flat with a row of grooves in its underside; And the old-style V-belt you’d find in your typical 70s car.
The V-belts in particular are prone to damage from overtightening, and the wrong tension often manifests as a squealing noise. Over time they get shiny on the sides, which is a sign they’re on the way out. The next stage is pieces coming off.
If you catch squeals early in the belt’s life you can take it off, give it a clean, tension it right and all should be well. If in any case you can’t stop the squealing, you’re often better off replacing it.
They all carry numbers on the side – 10A, 12A and the like – which is to do with the width and angle of the vee, that affects the grip it gets on the pulleys. The wider and less acute the angle, the more grip they have.
You’ll find on bigger and older cars running lots of ancillaries – like an old American car with power steering and air – they’ll run a larger belt. It’s critical you get the right profile, otherwise it will always struggle to do the job.
The modern serpentine belts hold their tension better than the older style and grip better. They wear out, too, getting a series of fine little cracks along the inner surface as they start to fail.
They will take more power before they start to slip and, on a modern car, will be run through and over quite a complex path. Just to be safe, before you remove one, draw yourself a little diagram of how it runs, or maybe grab a photo with your mobile phone. Assuming you forget to do either of things, you can often get the info off the web.
You can now buy serpentine belts for just about every vehicle on the road. So if having the engine bay looking absolutely stock isn’t all that important to you, it’s likely you can get a serpentine kit that includes the appropriate pulleys, to suit your toy. Worth considering if you’re doing an engine build.
They can cover everything from your six-cylinder engine through to a small block Chev. The result is pretty trouble-free.
Like all things there are good quality versions and so-so. If in doubt, stick with known brands like Dayco or Gates, or the genuine part. In many cases you’re talking $60 versus $30, which is a false saving.