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Old 06-26-2003, 10:29 PM
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Roller chains usually fit tighter due to the roller design compared to the involute factory style chain. Clearance in a roller is determined by the clearance space between the pin and the roller, wear will make the chain looser and hence a new one should be snug.

Involute types (OEM STYLE) actually ride out farther on the sprockets to take up clearance and self adjust for wear as a result, this makes them particularly useful for high mileage/stock applications. This feature also reduces noise and will quell harmonics in the valvetrain. The best part...the higher it is loaded the tighter it becomes, a very desirable valvetrain characteristic.

The only reason to ever choose a roller over a stock involute type is for the higher tensile strength of the roller design, the pin is larger than the involute pin. I think most builders will agree that an involute type is by far the superior design for every application other than pure racing where durability at high rpm is more important than harmonic dampening and noise.

In most cases a steel gear involute design will be strong enough for any application, if you are breaking them and need a roller, you have other problems that need solving first. The exception to this rule is chains that must reverse direction such as overhead cam chains where an idler is required to take up slack, the roller can reverse because of it's symetrical design, the one sided involute cannot. There are reversing involutes available but they very thick compared to a roller and are typically used only for timing critical drives where self adjustment under load is of paramount importance (old punch card CNC machinery is a good example).

Unfortunetly the magazines make it out to be quite the opposite because a roller is sexy. :skeptic:
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