Index Fitting the Boom to the Rider

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Fit the Trike Boom to the Rider

Time to adjust the trike to the rider. We begin with getting the initial fitting to get the rider on the trike for some basic riding to experience the "Recumbent Grin" and on to the more tedious stuff for rides that may last for hours.

Rider Dimensions:

From the Rider Measurements page we identified the critical rider dimensions on your Rider Specsheet; you will need them.

  • Rider Height
  • Rider Weight
  • X-Seam
  • Back Length
  • Thigh Width

Also the rider will need to be wearing their riding shoes and typical riding clothing. No tight jeans or other apparel that may limit rider motion! It is essential that the fitting be done with every effort to keep the rider calm. When rider's feel pressured at all during a fitting they tense up. Read this instruction all the way through before cutting anything!

Stuff you'll need:

  • Tools to loosen Boom, Hand Grips, Seat, Front Deralleur Cable if equipped
  • Hacksaw
  • File
  • Vise (or a means to hold the Boom while cutting)
  • Razor Blades
  • Magic Marker
  • Ruler
  • 1/2" Closed Cell Foam 2' x 6' minimum
  • Double Sided Tape
  • 1/2"-3/4" Inner Diameter Heavy Duty Pipe Insulation or Swimming Pool Noodles, Two Pieces
  • Electrical Tape


Initial Fitting for a Rider Height 5' to 6'3":

Note: If the rider is taller then 6'3" the standard length Boom may not be long enough. Most but not all OEM's do manufacture extended Boom Lengths. Check with the OEM of interest in the event you need an Extended Boom.

Boom Length & Cutting

Keep in mind that fitting a shorter rider with "standard crank lengths" may not be the optimal method. Oversized cranks can a rider in the "ballpark" but will make fitting a bit more difficult and limited. See the table below on Optimized Crank Lengths.

1) If possible move the seat to the furthest forward position. Only a few trike models have forward-backward adjustment so don't be alarmed if yours does not have this feature.

2) Set the seat recline to the least recline/ furthest forward position position and tighten so it does not move with rider's weight. Mesh Seats should have straps tightened!

3) Loosen the Boom and move it all the way in until it stops. Tighten it just enough that it can still be moved with some twisting force. Mark the Boom with a felt pen where it enters the receiving collar of the Boom.

4) Loosen the hand grip mounts and position them to the closest position for the seat; tighten them just enough so they stay put but can be moved with some twisting force.

5) Have rider sit on trike with riding shoes on. Clip into pedals. Position one foot forward (full leg extension) one foot back on the pedals. The rider may need to slide their butt forward on the seat a bit to reach, that's OK.

6) Have the rider back-pedal a few revolutions while keeping the Boom lined up (not swiveling in the mount) - this helps to both relax the rider and prepares for the next measurements.

7) Position the rider's foot to the closest points of their heel to the Front Axle Tube. There should be at least 1" of clearance. Otherwise the rider may strike the Front Axle Tube while pedaling. For most rider's on most trikes, this is unlikely unless the rider has longer feet and shorter legs the normal. Do not remind the rider of this at that time as it may tensing them up. Measure heel clearance and write that down on the Rider Specsheet.

8) Put your hand in back of the rider's lumbar and have them relax on the seat back. Ideally the rider's extended knee will be bent about 5° rather then straight. It is vital to keep the rider in a relaxed condition so take your time and keep the rider calm.

    There should be even fairly pressure from the base of the back (lumbar) to the middle of the back.

    If the rider is reaching the Boom may need to be cut shorter.

    If the pressure at the middle of the back is greater then the pressure at the lumbar the Boom may need to be cut shorter.

    If the rider can reach the pedals with knees bent at 5° and even pressure between middle and lumbar region of back with rider relaxed, move the Boom forward one inch and repeat the lumbar pressure test.

If there is more then 1" of heel to Front Axle Tube clearance you will likely need to cut the Boom length. As the Boom is designed for taller riders if you cut it an inch too short for a shorter rider that won't be a problem unless you later want to fit a taller rider.

When cutting the Boom be sure to mark the length from the end! Don't make the mistake of cutting it where you originally marked it at full depth - yes, people have made that mistake before....

9) A simple hacksaw & file is all you need. Mark off the distance you want to cut, add maybe 1/2"-1" and carefully saw off the excess length. Use a file to remove all burrs from cutting so the Boom will slide back in the Frame Receiver without scoring from burrs.

10) Install the Boom all the way to the end, align the pedals and snug. Repeat steps 5-8. Sometimes it seems like the rider either gains or loses length, that's because they aren't calm. One of your most important duties is keeping them calm and relaxed.

So what if the rider needs a shorter Boom and they don't have enough heel to Front Axle Clearance?

There are only two options:

A) Move the rider forward. If the seat post ion is fixed you can add about 1" of padding. Cut two pieces of 1/2" foam padding and place behind the rider's back. Repeat Steps 5-8. This is the easiest and cheapest option, not necessarily the preferred option.

If the seat is removable it may require custom brackets to move the entire seat forward. Moving a seat more then about 1.5" forward begins to move too much weight forward on some trikes that results in braking instability, ie rear wheel lift under braking.

B) Shorter Cranks - Typically most trikes are fitted with 165mm-170mm cranks. Shorter riders will almost always favor shorter cranks to maintain comfortable knee angles. Considering there are 25.4 mm to an inch it is possible to increase heel clearance by 1" as well as reduce leg reach by 1" by installing shorter cranks. This is definitely a preferred option for shorter riders even if they can fit without cutting the Boom. See the table below for optimized Crank Length to X-Seam.

If the rider cannot be fitted by cutting the Boom and/or moving the seat forward less then 1.5" the trike is not designed within the range of the rider's size!

After Boom is fitted to length note the adjustments made on the Rider Specsheet:

  • Amount of material removed from Boom
  • Thickness of Padding added to Seat Back
  • Any bracket changes that moved Seat forward
  • Crank Length

Align pedals and tighten Boom to manufacturers specifications.

Basic Hand Grip Adjustments

These are just the basics

Shorter riders tend to have shorter arms; and keeping the elbows & wrists in a comfortable position is essential. In most cases Seat Backs will need to be more upright depending on the model.

On trikes with Direct Steering positioning the Hand Grips may be a little more forgiving in a straight forward position, but as the Grips are moved closer to the rider they also tend to interfere more with the rider's thighs on tight turns.

On trikes with Under Seat Steering the bar can pivot in the center so as the bars are rotated back closer to the rider the wrist angle falls outside a comfortable range. One way to offset that is with extended Grips. Some trikes use a standard handlebar stem between the pivot point and the handlebar and on those models it is possible to extend the handlebars back another 1-2" with longer stems.