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What is a Cog Belt?

Lori Kilchermann
Lori Kilchermann

A cog belt is a high-performance belt used in applications where slippage or failure must be avoided. Made of rubber with cogs or nubs running all along the inside of it, the cog belt is designed to interlock with grooves or notches on the drive pulley. This interlocking design allows the cog belt to operate without slippage even at high engine speeds. Much like a chain and a sprocket, the cog belt can turn engine accessories without the fear of failure or slippage traditional rubber V-belts — or fan belts as they are most commonly called — are known for.

A byproduct of using a cog belt drive system has become a sought-after sound in the world of hot rod and high-performance automobiles. The telltale whistling sound emitted from a cog belt-driven blower induction system on an engine is created from air being caught between the belt and the pulley on the blower. Some enthusiasts choose to drill small holes in the drive pulleys on these systems in order to let the air escape and quiet the whistling. Alternatively, others choose to run an even wider drive belt system in hopes of trapping more air and increasing the volume of the whistling.

Woman with hand on her hip
Woman with hand on her hip

The cog belt drive system has two types of cogs. The most traditional style of cog utilizes a rounded tooth or cog on the belt. This does a good job of driving the cog system, but they are sometimes prone to jumping out of the pulley and slipping under duress. The better drive systems use a flat, square drive cog that fits tighter into the pulley and is more slip-resistant. This is often referred to as a Gilmer drive system. Many timing belts in automobile engines use this type of belt.

The main advantage of the cog belt is that it can run at higher engine speeds and pull a greater load with the least tension placed against it. By operating at a lighter tension, the belt runs cooler and has a much greater lifespan than a severely tightened belt. The belt can be operated without additional cooling provisions, such as an oil bath, and is much more durable than a chain and sprockets set-up.

Durability, reliability and light weight all combine to make a cog belt drive system practical in automobiles, airplanes and sea-going vessels. Both high-performance uses as well as assembly line and common-use applications depend on the belt drive system to operate properly for an extended time.

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Discussion Comments


@David09 - I like the fact that these belts last longer than regular belts, according to the article. There must be differences in cog belts, however, even those used as timing belts.

I had to change a timing belt on a Honda at only 65,000 miles. Apparently this is standard for the Japanese cars, but I would have preferred if I had not had to change it until 165,000 miles instead. At 65,000 miles, I will have to make that replacement at least twice during the life of the car.


@Mammmood - I don’t think that you’re reading it correctly. The cog belt is used in regular automobiles, in the timing belts.

I think it’s pretty standard actually. I don’t know about the whole whistling thing for race cars; perhaps those belts are enhanced somehow. But cog belts have indeed entered the mainstream of automobile usage.


So I take it that the cog belt pulley system is used on the race cars and not your standard automobiles? The article doesn’t say but I infer that this is the case, since it mentions that the high pitched whistle sound is a much desired byproduct of the cog belt design.

My car doesn’t make sounds of any kind unless something is broken. I am sure you can probably get cog belts for regular cars, or you can “soup up” your existing automobile, but I don’t see what the purpose would be.

The idea is that these belts are ideal for high speeds, so that you don’t have any slippage. I don’t think you would plan on racing your regular car; so the standard belt and pulley system should suffice in that case, I would think.

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