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How to figure out the BCD my chainring has

5 min read

Asked by: Leslie Ramos

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 do I know my BCD?

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).

What are the standard BCD for chainring?

The most common crank BCDs are: 130, 110, 107, 104, 94. the BCDs of less than 110 are made to accept chainrings smaller than 34 teeth.

What is the difference between 110 and 130 BCD?

Quote from video: Using a 55 on a 110 or a 130 BCD. That all depends on the chain ring being used and also how much power you are kicking out so it's a very tough one to actually answer interestingly.

What is a 104 BCD crankset?

104 BCD is the most common bolt pattern on double and triple cranksets and happens to be the first product ever made by Wolf Tooth Components. The Drop-Stop® tooth design is the best performing and longest lasting wide/narrow chainrings on the market.

How do you find a bolt circle?

How To Measure Bolt Circle Diameter

  1. Step 1 – Measure Bolt Hole ID and Zero the Digital Caliper.
  2. Step 2 – Measure Diametrically Opposed Bolt Hole Back To Back Distance.
  3. Step 3 – The Digital Caliper Readout Is Now the Bolt Circle Diameter.

What BCD are Shimano cranks?

110mm BCD

That’s changed with newer Shimano road cranksets, which have settled on 110mm BCD for all chainring sizes, giving you the option to increase or decrease your chainring sizes without having to change the cranks as well. SRAM’s crankset BCDs vary between setups, though.

What is the smallest chainring for 130 BCD?

Smallest 130 bcd is 38t. Any smaller and the bolt spacing would be in the teeth of the chainring.

What BCD is Shimano XT?

96 mm BCD

96 mm BCD Chainrings (Shimano XT M8000 and SLX M7000)

Are all chainring bolts the same size?

Single bolts are generally between 3.5 – 5.0mm Long. Double bolts are generally between 5.0 – 6.5mm long. Triple bolts are generally 7.0mm or longer. Triple bolts are normally only used to hold the two outer chainrings as the inner will be smaller and screwed directly to the crank.

Are oval chainrings better?

As a direct consequence, Oval rings enhance a cyclist’s ability to spin with a smoother power delivery and feel much easier on legs while climbing. Meaning you will go faster and get less tired. You will actually feel your pedal stroke to be more “round” with an Oval chainring than with a round chainring.

What do the numbers on a crankset mean?

The numbers on the chainrings simply refer to the number of teeth on each chainring. A standard road bike crankset will have the 53 and 39 tooth rings (obviously the 53 tooth ring is the large one and the 39 tooth one is the small one), while a compact crankset typically has 50 and 34 tooth rings.

How does a narrow wide chainring work?

The sole purpose of the narrow wide chainring is chain retention. The narrow wide tooth pattern keeps the chain from moving left to right and eventually popping off the chainring while riding. No one likes to drop their chain on the trail, especially in a race scenario where every second counts!

What is the difference between PCD and BCD?

Chainrings are sold by number of bolts and PCD or BCD, which is the same thing and stands for Pitch Circle Diameter or Bolt Circle Diameter. Easier than diameter to measure is the centre-to-centre distance between two adjacent bolts.

What is a bolt hole circle?

Wiktionary defines a bolt circle as a theoretical circle on which the centerpoints of bolt holes lie when the bolt holes are positioned as equally spaced in a circle. In DSM, a bolt circle annotation can only be placed in 3D mode on holes drilled in to solids.

How do you measure bolt circle flange?

How To Measure Crank/Chainrings Size BCD

How does a BCD work?

The buoyancy compensation devices (BCD), are the devices that give a scuba diver control with their buoyancy during a scuba dive. Basically the BCD allows the diver to inflate or deflate the device of air, allowing the diver to sink or rise when in the water.

What is a BCD in scuba?

Imagine scuba diving while hovering, weightless underwater – eye to eye with a fish. How is it possible? It starts with your buoyancy control device (BCD). A BCD does exactly what its name describes – it gives you control in the water. Sometimes you want to float on the surface comfortably.

How long will a BCD last?

If the hose is sound with no signs of cracking, there are no leaks, buoyancy control is good and you service the inflator and dump valves annually after the first five years of use, then you should still have a reliable BCD.

What are the different types of BCD?

The three most common types of scuba BCDs are jacket-style BCDs, back-inflate BCDs and backplate and wing combos. Each offers a different way of helping divers establish neutral buoyancy and offer different benefits for various diving styles.