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Drivetrain Questions Answered

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Most riders don't think much about maintaining their bike's drivetrain. Hopefully you are at least keeping your chain lubed and wiping off any grime that can build up on the chain, chainrings, cassette cogs, and the rear deraileur's pulley wheels. Keeping them clean and lubed is the best way to prolong the life of these components, but the chain will eventually "stretch" and the teeth on the the rings, clogs, and wheels will wear.

Chain lube is great for preventing rust and keeping the chain plates, pins, and rollers moving silently. The "in's and out's" of chain lube could be an entire blog in itself.  Long story short, you should have a bottle of each, but, riding around Vermont you'll probably reach for the wet lube more often.  Dry is for the most dry conditions while wet lube lasts longer and is more useful in our climate.  If you have questions about lube you can always give us a call or sign up for our "Clean & Lube Clinic" which is Thursday, July 26th at 5:30pm.   

While critical, lubricants do attract dirt and dust, effectively creating a grinding paste that will eventually elongate the chain pin holes in the chain plates.  It is the elongation of these pin holes that cause the chain to stretch. As the pin to pin distance increases the teeth in rings, cogs, and wheels are also worn causing the curve between each to "ovalize" as well. Replacing the chain before it elongates too much will prolong the life of rings, cogs, and wheels.

We use the Park Tool CC-3.2 to measure chain stretch and determine whether or not to replace it. Most manufacturers suggest replacing ten and fewer speed chains when the 0.75% side of the gauge just fits the chain. Eleven and twelve speed chains should be replaced when the 0.5% side just fits. Alternatively, you could measure 23 links from center of pin to center of pin. New chains measure exactly 12 inches, and you should replace your chain before it stretches more than 1/16 of an inch.

Multi-speed chainring and cassette cog wear can be difficult to determine visually because the teeth are not uniformly shaped when new. Teeth are engineered with differing profiles and chamfers, as well as pins and ramps, to assist in smooth shifting between rings. Because of this we recommend that you replace these parts if you are replacing a chain that has stretched beyond the limits listed above. If you do not, the new chain will likely skip off of the worn rings.

So, if you take just a couple things from this blog, remember to keep your chain cleaned and lubed, replace your chain before it is too worn, and let us know if you need a hand or some advice. The shop is open 9am to 5pm on Sundays, and 9am to 6pm every other day. FYI, we are hosting shop rides every Sunday in the summer and running clinics every other Thursday beginning July 12th. Come see us at MountainOps!


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