How To Set Chain Length On A Full Suspension Mountain Bike

Full suspension mountain bikes often need slightly longer chain length than hardtails because the distance between chainring and cassette grows as the suspension compresses.

Getting chain length right on a full suspension bike is more complex than on a hardtail. Too short and you risk damaging your derailleur or frame when the suspension bottoms out. Too long and you'll experience chain slap and poor shifting.

Why Full Suspension is Different

The Problem: Changing Chainstay Length

On a hardtail, the distance from the bottom bracket to the rear axle (chainstay length) is fixed. But on a full suspension bike, this distance changes as the suspension moves through its travel.

What happens during compression:

• Rear wheel moves rearward (on most designs)
• Effective chainstay length increases
• Chain needs to be longer to accommodate this growth

Axle Path Matters

Different suspension designs have different axle paths:

Design Type	Axle Path	Chain Growth	Examples
Single Pivot	Rearward arc	High	Some DH bikes
Horst Link	Variable	Moderate	Specialized FSR
VPP/DW-Link	Backward then forward	Moderate	Santa Cruz, Ibis
High Pivot	Strong rearward	Very high	Forbidden, Norco Range

High-pivot designs with idler pulleys have the most chain growth and require the most careful sizing.

The Standard Method: Sag Plus Full Compression

Step 1: Set Your Sag

First, set your suspension to normal sag (typically 25-30% of travel):

1. Sit on the bike in riding position
2. Have someone measure the shock stroke used
3. Adjust air pressure until sag is correct

Step 2: Calculate Base Chain Length

Use the standard formula with your bike at sag:

• Measure chainstay length at sag
• Note your largest chainring and sprocket
• Calculate using L = 2C + (F+R)/4 + 1

Or use our Bicycle Chain Length Calculator.

Step 3: Check at Full Compression

This is the critical step for full suspension:

1. Remove the shock or fully compress the suspension
2. Shift to the largest chainring and largest sprocket (big-big)
3. Check that the chain wraps around both without binding
4. The rear derailleur cage should not be pulled completely straight

If the derailleur cage is maxed out: Add 2 more links and recheck.

Step 4: Check at Full Extension

1. Let the suspension extend fully (or use a strap to hold it down)
2. Shift to the smallest chainring and smallest sprocket (small-small)
3. Ensure the derailleur still maintains tension
4. Chain should not slap or bounce excessively

How Many Extra Links for Full Suspension?

As a general guideline, add extra links based on travel:

Suspension Travel	Extra Links vs Hardtail
100-120mm (XC)	+2 links
130-150mm (Trail)	+2 to +4 links
160-170mm (Enduro)	+4 links
180mm+ (DH)	+4 to +6 links

Note: These are starting points. Always verify with the compression test.

Special Cases

High-Pivot Bikes with Idler Pulleys

Bikes like the Forbidden Druid or Norco Range use idler pulleys to manage chain growth. For these:

• Follow manufacturer's specific instructions
• Chain routing is different from standard bikes
• May require significantly longer chains

Coil Shock Bikes

Coil shocks can be harder to fully compress for testing:

• Use a strap to pull the suspension down
• Or calculate maximum chain growth mathematically
• Add 2 extra links for safety margin

E-MTBs

Electric mountain bikes often have:

• Longer chainstays to accommodate motors
• Different suspension kinematics
• Check manufacturer recommendations specifically

The Zip-Tie Method (Alternative Approach)

If you're unsure about measurements:

1. Start long: Install the chain 4 links longer than calculated
2. Ride the bike: Test on varied terrain
3. Check for issues: Look for:
   • Derailleur stretched at full compression
   • Excessive sag at full extension
4. Adjust: Remove links as needed

This is slower but reduces risk of a too-short chain damaging components.

Manufacturer-Specific Guidelines

Some manufacturers provide chain length specs:

Specialized

• Often provide chain length in owner's manual
• SWAT tools may include chain length reference

Santa Cruz

• Geometry charts include chainstay length
• VPP design has moderate chain growth

Trek

• ABP suspension has well-documented behavior
• Check Trek's support database for specific models

Yeti

• Switch Infinity platform unique chain requirements
• Consult dealer or manual

When in doubt, contact your bike's manufacturer or check their online resources.

Calculating Chain Growth

For the technically minded, you can estimate chain growth:

Chain Growth = (Chainstay at bottom-out) - (Chainstay at sag)

Most trail/enduro bikes see 10-20mm of chain growth, which translates to about 2-4 extra links.

Common Mistakes

1. Measuring Only at Sag

The most common error. Always check at full compression.

2. Forgetting the Big-Big Test

Even if you rarely use big-big, the chain must fit this combination.

3. Not Accounting for Suspension Progression

Progressive suspension may bottom out harder than expected.

4. Ignoring Manufacturer Recommendations

Some frames have very specific requirements.

Signs Your Full Suspension Chain is Wrong

Too Short

• Derailleur cage pulled straight at full compression
• Clicking or binding at full travel
• Inability to shift to big-big
• Potential derailleur or frame damage

Too Long

• Excessive chain slap
• Chain dropping in rough terrain
• Poor shifting in small-small
• Derailleur cage bouncing

See our full guide: Is Your Bike Chain Too Long or Too Short?

Quick Reference: Full Suspension MTB Chain Lengths

Travel	Chainring	Cassette	Chainstay (sag)	Approx Links
120mm XC	32T	10-51T	430mm	114 links
140mm Trail	32T	10-51T	437mm	116 links
160mm Enduro	30T	10-52T	440mm	118 links
180mm DH	32T	10-50T	445mm	118-120 links

Use the Calculator as a Starting Point

Our Bicycle Chain Length Calculator gives you the base calculation. For full suspension bikes:

1. Enter your chainstay length at sag
2. Get the calculated chain length
3. Add 2-4 links based on your travel
4. Verify with the compression test

Related Guides

• How To Calculate Bike Chain Length - Basic method
• Bike Chain Length Chart - Quick reference
• Is Your Chain Too Long or Too Short? - Troubleshooting
• How To Shorten A Bike Chain - Adjustment guide
• 1x vs 2x vs 3x Chain Length - Drivetrain comparison