The drivetrain on a bicycle is the mechanism that transfers power from the rider to the rear wheel and propels the bicycle forward. Technically the crank, pedals, bottom bracket, chain, cassette, and freehub body are all part of the drivetrain. Because I plan to write about cartridge bearings and pivots on another day I will focus on the chain and the components it directly engages with for now.
The chain on your bicycle is made of links, each link has two inner plates and two outer plates, a bushing and a pin. Your chain engages with the teeth on the pulley wheels of your derailleur, the gears of your cassette, and the chainring on your crank. Most of us don’t consider our chain much until it falls off or starts squeaking. Some riders systematically lube their chain before or after every ride. Grand tour road bike racers swap out their chain after each day’s stage. I recommend a more manageable and sustainable approach and will explain to you why drivetrain care is crucial.
One of the most expensive and avoidable repairs to your bicycle is a drivetrain replacement. Over time the pins in a bike chain wear down. As the pins get smaller the chain effectively gets longer, this is called “chain stretch.” A stretched chain grinds the teeth of a cassette, chain wheel, and pulley wheels. Eventually, the chain will break. A new chain will no longer be compatible with the now deformed teeth of your cassette etc. A drivetrain replacement will cost you hundreds of dollars, or worse, the parts you need won’t be available for purchase again until October, and you will be forced to take up trail running.
How do you avoid becoming a trail runner? Easily, and inexpensively. Keep your drivetrain clean. When you bring your bike to me for service here is how I do it:
I use water and highly diluted Simple Green, or biodegradable dish soap to gently wipe away dirt and dust. I remove the rear wheel and wrap the brake rotor in a clean dry rag (to protect it from splatter) I scrub the cassette with a toothbrush, I run strips of fabric between the gears to pull out all sorts of debris. I unwrap the rotor and replace the wheel. I pop the clutch open on the rear derailleur and use something like a dental tool to scrape hideous amounts of caked greasy mud and dust from your pulley wheels. It is satisfying and gross.
I liberate more grease-dust clumps from the inner plates of your chain. When I am done I imagine I’ve removed a quarter cup of debris.
I add lube to the now clean chain, one drop per link, and shift up and down the cassette so the lubrication can find its way to the bushings of the chain. I usually let it sit for a few minutes before wiping off the excess.
The purpose of the lubrication is to allow the inner and outer plates to flex and rotate smoothly as the chain snakes around and around. You do not need much on the exterior of the chain. Excessively lubricated chains collect dust and tiny rocks, this gravely greasy mixture acts like wet sandpaper and erodes the integrity of your precious drivetrain.
You do not have to do everything I do when I service your bicycle. I recommend a few simple
things instead.
1. Only add lube to a clean chain. Come into Habitat and check out our biodegradable wet and dry lubes.
2. Wipe off excessive lube after each application.
3. Wipe your chain often. If you do not have a repair stand flip your bike upside down and hold a clean dry rag around the chain while you rotate the pedal with your other hand. Old t-shirts work the best. Pass the chain completely through the rag a few times.
4. Periodically check your chain for stretch and replace somewhere between 50% and 75%. I have a “chain checker” and will happily check your chain for free. A periodic chain replacement is a good idea. A chain usually costs between $30 to $60 and that seems a small price to pay for not having to be a trail runner.
Thanks for reading! Habitat is open 7 days a week! Come see us between 10am and 6pm, or call for an appointment. Stay on the lookout for the next blog about brakes.
Images and words by Carolyn Keefe