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***If your bike has rectangular tubing, click here***

The Universal 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 trike with different riders. The installation is simple, design is sleek and materials are strong. If more than one person rides your trike, then a Universal Boom Adjust Chain Tensioner is perfect to eliminate the worries of whether the chain is too long or too short! We make the mounting clamps in a wide range of sizes, so let us know your trike/bike make and model, we'll figure it out from there.


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 to the main tube. 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 that comes in various sizes, specifically machined for the boom tube of your trike so that goes right on. The rear goes to the main tube, with its own clamp that is machined to fit your main tube. Let us know what make and model of bike or trike you have, and we'll set you up with machined clamps in exactly the size you need.

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 derailleur, so the effect is less than a derailleur 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.


Installation involves choosing the mounting locations, attaching the arms, installing extra chain, and making final adjustments to the S bend. Installation requires only a 4mm Allen wrench and should take about 8 minutes.

  1. First, choose the front mounting location. The front arm clamp goes on the sliding boom. It needs to be behind the chainrings but far enough forward that you can slide the boom back as far as you need. 
  2. Then, choose the rear mounting location. The rear arm clamp goes on the main tube. It needs to be clear of the boom clamps, bottle holders, etc. It needs to be far enough back that it won’t contact the chainrings when the boom is all the way back, and far enough forward that the idlers will still overlap when the boom is all the way forward. 
  3. Next, attach the arms. Clean the area of the frame where the clamps will go. Loosen the 5mm clamp arch bolts and remove the arch. Position the main clamp on the frame, then reinstall the arch and m5 bolts. As you tighten the bolts, make sure they are screwed in evenly. Sight from the front to check that everything is vertical, then tighten the bolts medium hand tight (no need to overdo it). 
  4. Route the chain and adjust the arms. Wrap the return chain around the idlers as shown. If you need to add chain, the usual amount required is a little less than a foot.  You can purchase additional chain here: 9-Speed Chain or 10-Speed Chain.

Rotate the cranks to make sure everything is flowing smoothly, and go take a test ride!


  • We originally designed the idea 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, and that it wasn't just an item for Catrikes!
  • One of the requirements was that it would handle the full range of boom adjustment. We originally designed something with a derailleur, but it wasn't possible to get the needed range. So, we went for it and made this. Ball bearing idlers, custom machined clamps, 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 comes in a crazy variety of sizes, machined specifically for boom tubes, which are sometimes odd sizes. The rear clamp comes in every known main tube size from 36mm up to 60mm, from 1.5in to 2.0in. The lengths of the arms are 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.
  • Available Clamp Sizes: 36mm, 40mm, 54.2mm, 55mm, 60mm, 1.5in, 1.625in, 1.75in, 1.8in, 1.847in, 1.885in, 2.0in, Greenspeed Anura rectangular tubing, Greenspeed GT20 rectangular tubing, Greenspeed Magnum rectangular tubing...
  • The clamps and arms are used in pairs, one on the main tube with the arm pointed forward and one on the boom with the arm pointed backwards. Here are the typical combinations:
    • 60mm + 54mm = HPVT, Azub, GS Magnum, AL Actionbent
    • 2" + 1.875" = TiTrikes, steel Actionbent
    • 2" + 47mm = Trident
    • Florida Arm + 1.8" = Catrike
    • 1.75" + 1.625" = ICE, non Magnum Greenspeed, Edge
    • 1.75" + 1.5" = TT Rambler, steel TW Bents
    • 40mm + 1.8" = Steintrikes
  • Normally, the front clamp is positioned just behind the chainrings, with the front arm spaced out away from the clamp, while the rear arm is flat right on the rear clamp. On the Azub trikes, the main tube is long and the boom tube is short. The boom inserts into the main tube almost up to the BB shell. On the Azub, the arm spacer is moved to the rear so the front clamp can go all the way up by the BB. Since the arms are now swapped inside for outside, the idlers need to be swapped inside to outside also. If you let us know you have an Azub, we do this for you.
  • This kit is designed to fit on most any trike on the market. That's why we call it the Universal Chain Tensioner! Just let us know the make and model of bike or trike that you have, and we'll make sure you get the right sized CNC machined mounting clamps.
  • Also known as a Chain Gobbler