50.4mm Bolt Circle Diameter, 5-Bolt chainrings

50.4mm Bolt Circle Diameter (BCD), 5-Bolt chainrings on this page:
Stronglight 49D: 53-tooth

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Bolt Circle Diameter is the diameter of the circle formed by the centers of the chainring fixing bolts. With 4-bolt cranksets, this is easy to measure. 5-bolt cranks are more difficult.

If you are unsure about what size chainring you need, Wolf Tooth Components has an excellent guide to measuring your rings.

Both Stronglight 49D and T.A. Cyclotouriste made outer chainrings that bolted to the base of the right crank arm with a BCD of 50.4mm. But, because the BCD for the inner rings that bolt to the T.A. and Stronglight big rings are different, the chainrings are not completely interchangeable. If changing makers of one of these big rings, the inner ring has to be swapped out as well.

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Stronglight 49D 53-tooth chainring. Used, $50.00/each

Here's the 53-tooth ring we have for sale.

Here's the back of the ring.