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The Catrike Boom Adjust Chain Tensioner allows you to move your boom without hassling with the chain. It automatically compensates for changes in chain length when you adjust the seat for different riders. Perfect for anyone that would like to share their Catrike with different riders. The installation is simple, design is sleek and materials are strong. If more than one person rides your Catrike, then a Catrike Boom Adjust Chain Tensioner is perfect to eliminate the worries of whether the chain is too long or too short!


1. So I can move my boom in and out all I want and I don't have to change anything else?

Yes. You're free to move the boom as much as you'd like, and you won't need to mess with the chain at all.

2. How does it work?

One end clamps to the boom tube, and one end clamps under the boom clamp Quick Releases. Each end has a chain idler on it. The return chain goes through the idlers in an S curve. As you move the boom in and out, the length of the S curve automatically compensates for the chain length change from moving the boom. It's super simple.

3. What kind of range does it have?

The same as the full range of movement of the boom.

4. Is it hard to install?

Not hard at all. The front clamps on to the boom tube with a clamp specifically machined for the Catrike boom tube, so it goes right on. The rear goes under the boom adjust Quick Release nuts. Loosen the nuts, slip the plate on the QRs, and put the nuts back.

5. Does it add drag?

A little. It's in the return side of the chain, so the tension is low. The idlers run on ball bearings, and are larger than the jockey wheels on a deraileur, so the effect is less than a deraileur would add.

6. Do I need more chain to go with this?

You will likely need more chain.  About a foot is more than enough.  You can purchase additional chain here: 9-Speed Chain or 10-Speed Chain.

7. Are you going to make things like this for other trikes?

Yes, other versions are in the works. Let us know what trike you would like us to do next.


Installation consists of attaching the front clamp, attaching the rear plate, installing the extra chain, and adjusting the S bend. Installation requires only a 4mm Allen wrench and should take about 8 minutes.
  1. First attach the rear plate. Open the boom adjust quick releases and loosen and remove the nuts. Slip the plate over the QRs,  reattach the nuts, and tighten the QRs again.
  2. Next, open the front clamp and attach the front arm to the boom. Position it so the clamp is just behind the back edge of the big chainring. Sight from the front and line it up vertically with the chainrings and tighten the clamp. The angle of the arm is adjustable to fine tune the S bend. Adjust the arm so it's idler is higher than the rear idler by about 3/4 inch.
  3. Shift into the small cog in back and the small chainring in front. Rotate the cranks around to bring the chain's existing Quick Link to a convenient place. Open the Quick Link and attach a new section of chain. Finally, lay the return chain through the new idlers in an S bend. Put the return chain under the lower idler, then up, behind, and over the top idler.
  4. Rotate the cranks to make sure everything is flowing smoothly, and go take a test ride!



  • We originally designed this kit at the request of Catrike. They wanted something for dealers to be able to easily offer test rides without having to lengthen or shorten the chain. It was such a hit that it became clear it wasn't really just an internal Catrike item for dealers. We talked and decided it was best for us to take it public and sell it directly.
  • One of the requirements was that it would handle the full range of boom adjustment. We originally designed something with a deraileur, but it wasn't possible to get the needed range. So, we went for it and made this. Ball bearing idlers, custom machined clamp, the works. The response has been overwhelming, it has been hard to keep them in stock at times.
  • All parts are black anodized CNC machined 6061 T6 Aluminum. All fasteners are stainless steel. The idlers are Delrin with 6mm sealed cartridge bearings.
  • The front clamp is machined specifically for the Catrike boom tube, which is a special custom size. The length of the front arm is designed to cover the full range of boom adjustment.
  • No particular maintenance is required. The idlers are high quality and have sealed cartridge ball bearings that will outlast the other parts of your drivetrain by several times.
  • Also known as a Chain Gobbler