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Frequently Asked Questions

Technical

(FAQ 1 of 5)>>>

What do I need to know to buy new chainrings for my crankset?

First, check your chainrings (sometimes called "chainwheels") to make sure they need replacing. In general, the rings you ride in most wear quickest and usually they're also the smaller rings. So check those regularly.

To do this, simply inspect the teeth shapes closely. Because the smaller rings wear fastest, there's a good chance the large rings will be in good condition, which allows comparing the teeth on the large ring with the teeth on the ring you think may be worn out. If the teeth look smaller and hooked, it's a sign that the chainring is worn out.

However, don't worry if a few teeth on each side of the chainring appear smaller than the others. On some rings they're actually made that way to act as "shifting gates," an innovation that improves shifting. As long as the majority of the teeth look full and resemble the ones on a good chainring, the ring is okay.

Sometimes you'll feel a worn chainring after you've replaced the chain. There will be a roughness in the pedal stroke because the new chain won't mesh perfectly with the old teeth. Another symptom of a worn chainring, usually on a mountain bike, is something called "chain suck." This is when the chain gets pulled up by the worn teeth on the ring while you're pedaling and gets jammed between the chainring and the frame. Usually, replacing the ring solves the problem.

In an extreme case, a completely worn-out ring can even allow the chain to skip when you're pedaling hard or climbing. What happens is the teeth can no longer hold the chain under pressure and the links actually lift up and over the teeth creating an annoying and dangerous hiccup in your pedaling, which is best described as "skipping" for the way the pedals jerk forward when the chain slips.

It's also possible to ruin a chainring by bending it while trying to ride over a log or railroad tracks. Or even by getting your pants caught in the teeth.

If you're not sure whether your chainring(s) needs replacing, we're happy to take a look and let you know. Chainrings vary in design and size. You can just bring your old one in for us to match up, or if you'd rather, you can look at your chainring and give us the following details:

  • The brand and model and type, such as Shimano (brand) XT (model) 9-speed (type).
  • The number of teeth on the chainring (usually stamped on the side; or you can simply count).
  • The number of chainring bolts (usually 4 or 5).
  • The Bolt Circle Diameter (BCD). This is the measurement of an imaginary circle on the chainring bisecting all the bolt holes. The best way to determine this is by measuring the exact distance (center to center) between 2 adjacent bolt holes. Then find that number on the correct chart below to determine the BCD for your chainring.

BCD chart for 5-bolt chainrings

Bolt to Bolt (measure center to center) Bolt Circle Diameter (BCD)

32.9mm

56mm

34.3mm

58mm

43.5mm

74mm

55.4mm

94mm

64.7mm

110mm

76.4mm

130mm

79.5mm

135mm

84.6mm

144mm

BCD chart for 4-bolt chainring

Bolt to Bolt (measure center to center) Bolt Circle Diameter (BCD)

41mm

58mm

45.3mm

64mm

48.1mm

68mm

73.6mm

104mm

79.2mm

112mm

If you have any questions at all, just ask and we'll be happy to help!

Technical

(FAQ 1 of 5)>>>
 

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