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 Size
Bolt Pattern
Best For
Smallest Chainring
Who Uses It
130mm
5-bolt
Standard road bikes
38T
Traditional road cyclists
110mm
5-bolt
Compact road bikes
33T
Climbers, recreational riders
110mm Asymmetric
4-bolt
Shimano road
34T
Shimano users (newer models)
104mm
4-bolt
Mountain bikes
30T
MTB riders (older standard)
96mm
4-bolt
Shimano MTB
28T
Shimano MTB (XT, XTR)
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.
This limitation is frustrating for riders who want very small chainrings for climbing.
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 system:
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. Annoying, right?
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, so you're not locked into one brand's ecosystem. Whether you prefer SRAM or Shimano chainrings, you have options.
Always confirm compatibility before buying, but with CRODER, you get flexibility that the big brands don't offer.
BCD vs Direct Mount: Side-by-Side Comparison
Feature
BCD System
1X Direct Mount
2X Direct Mount
Weight
Heavier (spider + bolts)
Lighter (no spider)
Heavier (two chainrings)
Stiffness
Good
Better
Good to Better (depending on design)
Smallest Chainring
Limited (30-38T depending on BCD)
Very small (24-28T possible)
Limited (similar to BCD)
Compatibility
Wide (if BCD matches)
Brand-specific
Brand-specific
Chainring Availability
Huge selection
Growing but limited
Growing but limited
Price
Generally cheaper
Generally more expensive
Generally more expensive
Ease of Change
Easy (unscrew bolts)
Easy (but need right pattern)
Easy (but need right pattern)
Best For
Road cycling, standard setups
MTB, gravel, modern single-chainring bikes
Road cycling, touring, wide gear range needs
CRODER Chainring Options
To match your specific crankset and riding style, CRODER offers chainrings in multiple configurations for both 1x and 2x setups.
Our chainring range includes:
Multiple BCD standards (110mm, 104mm, and more)
Direct Mount options (SRAM 8-bolt compatible)
Both 1x and 2x configurations
Various tooth counts (from climbing-friendly small rings to high-speed large rings)
Whether you need a 32T for steep climbs on your 1x mountain bike, a 50/34T combo for your 2x road setup, or anything in between—we've got you covered.
