Air can volume and shock tuning

The principle

For any given shock, the larger the air can volume, the more linear the air spring will be. Conversely, the smaller the air can volume, the more progressive the air spring will be.

What do I need? A bigger or smaller air can/volume?

Base line

Set your shock up with the correct amount of sag for your particular frame (typically 20-30%). If the manufacturer does not recommend a percentage, then start with 25% sag as pretty safe starting point for modern frames. Do NOT set your shock pressure using some recommended setting or a pressure your mate uses or some other crap you may have read on the internet. Do NOT waste your time with air can changes and mods if you have not set the shock up properly to get a decent base line.

If you really want to take methodical approach to this, ride the same track with 20% sag, then 30% sag and then 25% sag. Take note of what the bike is doing at each of those sag percentages. This will tell you everything you need to know about whether you need to change the volume of your air can, and which way you should be going.

How does it ride?

  • harsh bottom out: First try decreasing sag. If it still harshly bottoms out (or increased pressure makes the ride rough) then decrease air spring volume.
  • not getting full travel: run more sag by reducing pressure - try 30% sag. If this causes the bike to wallow in the mid-travel then increase air volume.
  • too much wallowing in the mid stroke? Try one of the newer twin chamber air cans.

How do I increase air volume?

It depends on your shock and air can:

  • if your shock has a higher volume air can available you can try that;
  • if your shock has a higher volume air can already, see if there are any volume reducers fitted that you can remove to increase volume;
  • if your shock has a high volume air can already and no volume reducers to remove, you may need to consider a different shock with higher volume air chamber.

How do I decrease air volume?

It depends on your shock and air can:

  • get a smaller volume air can;
  • fit volume reducers to the air can;
  • if volume reducers not available, make your own - you can  use rubber bands / suspension grease;
  • if smallest air can and volume reducers not working, get a different shock.

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