mechanical-advice

 

Information & Advice - Bicycle Chains

 

Info and advice appears below.

There's not much yet, but at least now we have somewhere good to put it!

Measuring Bicycle Chain Wear
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We use an old-fashioned and very simple method for assessing bicycle chain wear. It is based on the idea that a bicycle chain works pretty efficiently until worn to the stage that it "stretches" by one percent (gets 1% longer than when new). This allows for significantly more use (wear) than more modern chain-checking devices, and it is assumed that you will replace your cassette at the same time as you replace your chain. (Not doing so will result in the chain slipping over the rear sprockets when under high pedalling loads). Leaving the chain to wear significantly beyond this stage will result in a rough drivetrain, and the high likelihood that you'll need to replace your chainring/s also when replacing your chain and cassette.

To see how much wear a chain has, use a ruler marked in inches. Bicycle chains use a half-inch pitch, so when you line one rivet up at the beginning of the ruler, there will be (with a new chain)  a rivet at each inch marking on the ruler (each second rivet on the chain).

As a chain wears, it gets slightly longer, due to looseness in each connection in the chain. A chain has "stretched" 1% in length when the rivet at 11 inches moves to be at 11 and 1/8 inches. (To be precise, that's 1.13% stretch).

Using this guide, you can see how much "life" a chain still has in it (or how long ago you should have replaced it!).

Chain Suck
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Why does my chain jam up between the chainrings and the frame?

That's what's called chain suck - when the chain "sticks" to the chainrings and therefore gets pulled (sucked) up and jams against the frame.

It's usually caused by worn chainrings which develop a broadened front, which jams into the chain links when pedalling firmly. It will often only show when a new chain is fitted. Some brands of chain can be more forgiving than others of chainrings worn in this way.

It can also be caused by undue pedal pressure during front downshifts - there is too much tension on the chain and it can engage firmly on the smaller chainring while still being firmly attached to the larger chainring. Changing down with less pressure on the pedals will usually alleviate this problem.If you're in an uncomfortably high gear and need to downshift but don't have the momentum to ease the pedalling force, downshift on the rear sprockets first (they'll handle a bit more pressure than the front during shifts) before downshifting on the front.