You found the perfect chainring online. Great price. Looks amazing. You're about to click "buy"...
Stop.
If you don't check the chainring interface first, it might not fit your crank at all. Here's the truth: the interface determines what chainrings you can use. Get this wrong, and your new chainring simply won't attach.
Let's fix that in the next 5 minutes.
What is a Chainring Interface?
There are two common systems on cranksets:
BCD (Bolt Circle Diameter) - The traditional system
Direct Mount - The modern system
Let's start with BCD.
BCD: The Traditional System
What is BCD?
BCD stands for Bolt Circle Diameter.
Imagine drawing a circle that passes through the center of all the bolts that hold your chainring. The diameter of that circle is your BCD.
⭡ These 5 bolts form a circle, The diameter of this circle = Your BCD
Why It Matters
Your chainring's BCD must exactly match your crank's BCD.
A 110mm BCD chainring will NOT fit a 104mm BCD crank. Not even close.
Common BCD Standards
BCD
Bolts
Best For
Min Ring
User
130mm
5-bolt
Std. Road
38T
Roadies
110mm
5-bolt
Compact
33T
Climbers
110mm Asym.
4-bolt
Shimano
34T
Shimano Users
104mm
4-bolt
MTB
30T
MTB (Old)
96mm
4-bolt
Shimano MTB
28T
XT/XTR Users
How to Identify Your BCD
Method 1: Look for markings
Many cranksets have the BCD stamped on them. Check the spider (the arms that hold the chainring).
Method 2: Measure it
➜ Honestly?
Most people never need to measure. Your BCD is usually marked somewhere. But if you really need to measure:
For 5-bolt: It's more complex—better to just ask us or your local shop
For 4-bolt: Measure center-to-center between opposite bolts directly
BCD Limitations: The Tooth Count Problem
Here's the catch with BCD: each BCD has a minimum tooth count. Why? Because if the chainring gets too small, the teeth would overlap with the mounting bolts. Physics says no.
That's exactly why Direct Mount was invented.
Direct Mount: The Modern System
What is Direct Mount?
Forget bolts. Forget the spider. With Direct Mount, the chainring clicks or bolts directly onto the crank arm itself.
The crank has a mounting interface built in
The chainring has matching tabs or bolt holes
They connect directly - no middleman
Why Direct Mount Exists
Lighter weight - No spider, fewer parts
Stiffer - Direct connection = better power transfer
Smaller chainrings - No tooth count limit. Want a 26T chainring? No problem.
That third point is huge for mountain bikers and gravel riders who want easier climbing gears.
The Direct Mount Problem: Brand Compatibility
Here's the frustrating part: major brands use different Direct Mount patterns that don't work together. The two main systems are:
SRAM 8-bolt pattern (used by SRAM, RaceFace, and others)
Shimano pattern (proprietary, not compatible with SRAM)
This means a Shimano Direct Mount chainring won't fit a SRAM crank, and vice versa.
➜ How CRODER Solves This
This is exactly why third-party manufacturers like CRODER exist. We design our cranksets with broad compatibility in mind. The CRODER SPIRIT works with both major Direct Mount standards. Always confirm compatibility before buying, but with CRODER, you get flexibility.
BCD vs Direct Mount: Side-by-Side Comparison
Feature
BCD
1X Direct
2X Direct
Weight
Heavier
Lighter
Heavier
Stiffness
Good
Better
Good+
Min Ring
Limited
Smallest
Limited
Fit
Wide
Specific
Specific
Price
Lower
Higher
Higher
Best For
Standard
MTB/Gravel
Road
CRODER Chainring Options
To match your specific crankset and riding style, CRODER offers chainrings in multiple configurations for both 1x and 2x setups.
