What is the BCD dimension?
Bolt Circle Diameter (BCD) is the diameter of the circle that goes through the center of all of the bolts on your chainring. On bicycle chainrings, this dimension is usually measured in millimeters. It is critical to know the BCD of your crankset when you are selecting a new chainring for your bike. In many cases the BCD is printed right on the chainring like in the example below. Sometimes it is stamped or engraved on the back side of the chainring. If it is not labeled on your chainring, you will need to measure it. On a chainring with 4 bolts, the BCD is the distance between two bolts across from each other.
How to calculate a BCD?
If anyone knows the binary representation of the numbers 0 to 9, he/she can make a BCD code of any number because, in BCD, we just convert each individual digit of any number to binary and then write them together. BCD Conversion With BCD number system, the binary weight of each digit increases by a factor of 2. The first digit has a weight of 1 or (20), the second digit has a weight of 2 or (21), the third digit has a weight of 4 or (22), and the fourth digit has a weight of 8 or (23).Why do we add 6 to BCD addition? In BCD addition, if the sum of two digits exceeds 9, we add 6 to correct the result. This adjustment helps convert the binary sum back to valid BCD format, ensuring each decimal digit stays within the 0-9 range.
How to pick a BCD?
When it comes to choosing the right BCD, lots of factors will affect your decision. You’ll want to consider how much to spend, which type of BCD goes best with your diving style, how much weight you carry, where you want the jacket’s air to sit on your body, and even your body type. The Best Dive BCDs for 2025 are: Cressi Travelight BCD – Overall Winner, Best BCD. ScubaPro Litehawk BCD – Lightweight ‘Hybrid’ Travel Dive BCD. Oceanic Excursion BCD – Best Wing BCD with Pockets. Scubapro Hydros Pro / X BCD – High-End Modular Dive BCD.
Is my BCD too big?
If someone is diving with a BCD that is too big, the jacket will shift around during the dive. A too small BCD will sit too high on the waist or squeeze the diver when inflated. Again, it would better for beginners to stick with jacket, back-inflate, or hybrid style BCDs.