Accessory belt sheared along circumference: What causes this?

When driving the Focus yesterday, I heard a slapping racket under the hood. It was during a spirited canyon drive; 40 miles of 2nd gear kind of drive, so I assumed that I broke something. When I stopped, I saw that the accessory belt looked especially thin.

I replaced the belt today, and one taken off was missing 1-2 ribs all the way around. Otherwise, it was in great shape; no chunked ribs otherwise, no external cracking, and very minimal rib cracking.

The tensioner held tension, and I did not see any pulley obstructions. Everything seems to work fine, though the battery has been weakening since it made the cross-country journey (via truck). I replaced the battery last week. The A/C compressor has made a loud click when turning on and off, though it has done that for years.

Would this simply be from misalignment? While running, everything looked good under the hood.

Debris? Likely something like a small stone got flipped up in there and broke those ribs. Once they were broken, it was just physics that took it the rest of the way apart.

My first thought was a small stone or just a defect. Replace it and keep and eye on it.

Have a real close look at the alignment of all the pulleys. If one of the mounts or bearings is loosening up, the belt can climb over the high side, and then it cuts a rib off on the edge of the pulley.

Most common thing is the pivot bushing in the tensioner.

Old age?

How long was the old belt on there? Maybe the tensioner is slapping allowing the belt to jump.

I had a similar thing happen on my E36 race car. It was a misaligned power steering pulley due to a loose bolt.

"What causes this?"

Chinese people mostly . . .

I've recently had a number of repro parts fail or simple be SO poorly made that I didn't even bother installing them. I mean going so far as to having drill bits broken off and jammed inside the holes that were being drilled.

All of them provided by our Asian Trading Partners.

TeamEvil wrote: "What causes this?" Chinese people mostly . . .

Chinese people build to match a price point that American people have proven themselves willing to pay for.

Duke wrote:

TeamEvil wrote: "What causes this?" Chinese people mostly . . .

Chinese people build to match a price point that American people have proven themselves willing to pay for.

Better words have not been spoken. Devolving into a berkeley walmart thread in 3, 2, 1, GO!

Duke wrote:

TeamEvil wrote: "What causes this?" Chinese people mostly . . .

Chinese people build to match a price point that American people have proven themselves willing to pay for.

I forget who here said it.. but they have worked personally with Chinese manufacturers. They can and do build things that are beautiful to behold and designed to work flawlessly for years.. if you stay on top of them. If allowed, they can and will devalue their own work to save money in manufacturing just as much as any western company.. to keep that from happening, you have to stay ontop of what they are doing.

Most western companies do not mind getting substandard parts if they can save a few pennies too.. so it is the whole supply chain from designer to final customer that lets you discover brand new parts that are broken

I'd love to see a shovel or drill or even a pair of shoes that were manufactured for the Chinese home market.

Makes me wonder what The Chinese Repairman uses.

Misalignment or something rubbing on it.

Check the tensioner. They can wobble when they start to wear out.