The factory-original belt that drives the AC compressor on my '00 Chrysler 300m decided to disintigrate recently (first the inner 1/2 separated and got shredded in amongst the pulleys and then the outer 1/2 got noisy so I had to cut it and remove it).
This belt is behind the serpentine belt, so I figured I might as well replace both of them. A local parts store was offering the Goodyear Gatorback as a replacement.
The defining characteristic of these "gatorbacks" is that they have diagonal notches cut into them for some reason.
Here's a few pictures:
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I asked the parts guy why would I want a belt that was made intentionally weaker by having some of the belt material removed by cutting these notches on the inside. He said these were premium belts and the notches help to clear dirt from getting into or staying in the v grooves. I told him I didn't buy that argument, and the addition of these notches would make the belt noisier.
Note the package:
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"The quite belt"
Quiet my ass. You put those notches on the side of the belt that contacts the pulley or the v-grooves, you're going to have noise. The notches are at a bit of a diagonal so maybe that cuts down on some noise.
I had them order me some "normal" belts that haven't been intentionally weakened by the notch-cutting.
Anyone have the same (or different) take on these belts?
A google search seems to turn up some reports and pictures of early failure of these belts...
Most of the work done by the belt is along the very top, notice how thin serpentine belts are. That's how the gator back is designed, the strength is in the "top". By putting notches in it they eliminate heat buildup caused by the "bottom" of the belt having to squish itself together as it goes around pulleys. That squishing means not only that the belt is generating heat internally but it also means the sides of the belt are sliding up/down along the inside of the pulley as it enters and leaves the groove. That also generates heat and probably noise. I think the idea that the notches produce a cleaning action probably has some truth to it but I don't think that was the main reason they designed them as they did.
The belt transfers tension at the interface where it makes contact with the pulley. That is on the bottom side of the belt (if we're talking about a serpentine belt). The belt transfers that shear tension upwards to the rest of the belt material.
If you cut grooves in the bottom of the belt, you reduce the amount of contact surface that the belt makes with the v groove surface of the pulley, and you increase the shear tension of what-ever belt material you have left that you didn't cut away or remove.
I've read more about these belts, and the idea seems to be that as aftermarket replacements, the most common belt complaint is noise caused by mis-aligned or perhaps slightly bent pulleys - which is far more likely after thousands of miles and years of operation when the factory belt is at the end of it's life. Putting a notched pattern on the v-groove side seems to reduce any tendency to cause noise that an ordinary belt would produce.
I think the take-home message is that if a "normal" replacement belt doesn't make noise, then stay with it. If there is noise, then the Gator Back (aka "The Quite Belt" tm) will create less noise - if you take no steps to fix the pulley alignment in the first place.
Also reading the various comments about Gatorbacks, many people swear by Gates - and will use no other belt. Gates doesn't seem to make their own version of these notched belts - only Goodyear does.
Car designers have engineered the radius of the various pulleys to account for that. I'm sure they've worked closely with belt makers to insure the radius of curvature of the path the belt takes doesn't exceed what a given belt is designed to handle. You can't have an infinitely thin belt that generates no heat when it bends and then straightened out, because there is no belt material that is infinitely strong in shear or tension.
Serpentine belts don't really grab or come into contact with the sides of wide, multi-groove pulleys like a V-belt does.
It's clear that the Goodyear rep's have given the sales people at these parts stores a list of why the notches are a good thing, maybe even some of these were invented by Goodyear's marketing people - like the idea of some sort of self-cleaning action of road debris / dirt.
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