What is the Drivetrain?

If you’re a bicycle rider, you might have heard the term ‘drivetrain’ being bandied about by in-the-know bike riders. If you’re not a mechanical type of person, you may be wondering what this word means. You may be especially interested if you’re not the kind of person to do much preventative maintenance on your bicycle and if it has been riding a bit rough of late. Looking after your drivetrain, and replacing certain components within it if necessary, will ensure that your bike commute to work is a safe and smooth one.

What is the drivetrain and what does it do?

 The ‘drivetrain’ of the bike consists of all the bits that you use to push (or pull) the bike along.

From front to back, the key components are:

  1. Pedals
  2. Cranks
  3. ‘Chainrings’  (chainwheel)
  4. Chain
  5. Cogs (cassette)
  6. Derailleur


*Mostly, bike mechanics call the chain, cog/s & chainring/s (and derailleur wheels) the ‘drivetrain’ of the bike.

What causes the Drivetrain to wear/need replacement?

As you ride and change gears, the chain, chainrings, cogs and derailleur wheels pull and rub on each other. In the absence of an effective lubricant barrier between them (often washed or evaporated away by rain and sun, or flung off in use), metal-on-metal contact strips tiny shards of metal away from them, and/or ‘peens’ them out of shape, each time torque is applied to them, deforming the teeth of the chainrings and cogs, and wearing the internal and external parts of the chain. Fine grit flung up from the road by the tyres onto the chain and cogs exacerbates this as well, and when it is floating in rainwater, it multiplies the effect again. During the 10s of 1000s of revolutions that are pedalled, the drivetrain parts wear away, like the doorstep of an old building.

 How can I tell if it needs replacing?

The most common part of the drivetrain to wear out and need replacement is the chain. The easiest way to measure chain wear is with a chain checker tool that all bike shops will have. This tool will tell you if your chain is past the point of serviceability. If it is elongated past the recommended point, it is advised that you get a new chain and cassette (and potentially chain rings too) at the same time. If your drivetrain is noisy, hard to pedal, and, on derailleur systems, difficult to change between gears, then replacing these parts will invariably fix your problems.

chaincheckerWhat does it cost to replace?

This all depends on your bike and the quality required for replacement parts. For a chain and cassette replacement it could be anything from $100 (for parts and labour) up to $400+. If chainrings are needed, then this can add more on top. Give Good Cycles a call or email if you’d like to chat about this in detail.

I have just had my chain and cassette replaced, but now my chain is skipping – how can it be possible that I’ve got new bits, and spent money, and now my bike seems worse?

 Even if the workshop has done the job correctly initially, sometimes the remaining partly worn parts take a while to bed into and adjust to the new parts, and subsequent readjustment is needed during the first 50–100 kms. Most shops will do this for you free of charge, including Good Cycles, or show you how to perform minor tweaks yourself.