Rizal Philippines
March 4, 2018
It turns out that for crankset alone, a lot has to be learned. There are various questions that raised:
1. What is meaning of compact, midcompact, and regular crank?
2. What is a triplet?
3. Which of number 1 fits me?
4. What about BB?
5. Can I use MTB cranks for RB or vice versa?
6. How about chaning the blades (the chains of the chainsets)?
Crankset buying guide
Cheat Sheet for BCD (Bolt Circle Diameter) -Common Diameter of All Bolts in a Crank/chainset
Cheat Sheet For Finding Bolt Circle Diameter (BCD)
[table color=”grey” ]
| # Bolts in Circle | Measurement Between Adjacent Holes | Bolt Circle Diameter ( BCD ) | |
| Metric (Millimeter) | English (Inches) | ||
| 4 | 45.3 mm | 1.78 inch | 64 mm |
| 4 | 56.6 mm | 2.23 inch | 80 mm |
| 4 | 73.5 mm | 2.90 inch | 104 mm |
| 4 | 84.9 mm | 3.34 inch | 120 mm |
| 5 | 43.5 mm | 1.71 inch | 74 mm |
| 5 | 64.7 mm | 2.55 inch | 110 mm |
| 5 | 76.4 mm | 3.01 inch | 130 mm |
| 5 | 79.4 mm | 3.12 inch | 135 mm |
[/table]
Look at the photos and compare to your crank or chainrings. Find the number of bolts in the circle (Left Column) and the approximate measurement (metric or English) between adjacent holes. Find those numbers in the table, then in the Right Column you’ll see the Bolt Circle Diameter (BCD). Use this information to buy the correct chainrings for your bike.
__________
__________
Again, Please NOTE: This applies ONLY when the bolt holes are evenly spaced. It will not apply, for example, to the newer 4-bolt road cranks from Shimano and Campy because the holes are not spaced evenly.
These newer cranks also have a bolt circle diameter, but you’ll need to measure directly across opposite holes to get it — not, as shown in the cheat sheet, center-to-center on adjacent holes.
No comments:
Post a Comment