November 20, 2017

How To Add/Remove and Adjust Synapse Internal Frames

A close up of the Synapse 25 Frame in the Synapse 25.

We offer optional, removable internal frames with aluminum stays for the Synapse 19 and Synapse 25 backpacks.

If you're wondering if you'll need or want an internal frame for your Synapse, consider reading our Guide To Backpack Frames first.

How and When To Adjust the Curve of Your Synapse Internal Frame

We’ve bent the aluminum stay of the Synapse 19 and Synapse 25 Internal Frames to a generic spinal curve. If you find the curve comfortable out of the gate, you're good. But if you need or want to adjust that curve, it's easy to do — and you needn't remove the stay or frame sheet from the Synapse to do it. Keep in mind that the idea is that the frame follows your spine: if, in trying to adjust the internal frame, you end up with some whacky pretzel-looking thing, you perhaps need a chiropractor more than you need a backpack.

Watch this video for instructions on how to adjust the curve of your Synapse Internal Frame:

How To Install or Remove Your Synapse Internal Frame

Because the Synapses were not originally intended to accommodate an internal frame, they weren't designed with a way to attach one; this required us to make some modifications to the frame design. We took advantage of the loops for the Cache tablet/laptop sleeve at the top of the packs to retain the internal frame: a clever “T” bar holds the frame in place relative to the loops. The lower edge of the internal frame floats free in the Synapses—we’ve found this isn’t much of an issue as the contents of the bag tend to hold this lower extreme in place. Please note: your Synapse must have rail loops in order to use these new, optional internal frames. If your Synapse doesn't have rail loops, you're welcome to try using the internal frame anyhow; let us know how it works for you.

If you order the internal frame on the Synapse 19 or Synapse 25 pages along with the pack itself, it will come pre-installed. If you order the internal frame separately for an existing Synapse, or if you remove the installed frame and then want to add it back, check out the video and text instructions for internal frame installation and removal below.

1. Unzip the main compartment of your Synapse 19 or Synapse 25 and flip the rear top edge of the pack (the side against your back) to reveal the two loops of nylon webbing (“rail loops”) at the inside top of the padded back panel.

2. Insert the notched left and right ends of the T bar into the rail loops, centering the rail loops into the notches. Flip the T-bar up, inverting the “T”.

3. Slide the internal frame into the Synapse, making sure the center stripe of nylon webbing is towards the inside of the bag (away from your back), and the TOM BIHN label is right side up.

4. At the top of the center webbing stripe is a Velcro tab. Open the Velcro tab on the webbing, revealing the aluminum stay. You’ll need to “pop” the very top end of the stay out of where it sits in the upper end of the webbing sleeve. Do this by first making sure the Velcro tab is flipped upwards, then placing a thumb on either side of the stay and gently bending the top of the plastic frame sheet back away from the stay.

5. Tuck the Velcro tab into the slot on the T-bar between the rail loops. While flipping the T bar down, slip its center tongue behind the stay, between the stay and the center webbing stripe. Push the T-bar as far down as it will go. Seriously, all the way. Be sure to keep the left and right ends of the T-bar completely in front of the plastic frame sheet.

6. Pop the top end of the stay back into the upper end of the webbing sleeve. Do this by gently pulling the end of the Velcro tab forward over the top of the stay until it "pops" back into place. Re-engage the Velcro closure snugly. Flip the top of the main zipper back to its original position.

7. Load up and hit the trail!

Questions? Want help? We're here for you: or 1-800-729-9607 or +1-206-652-4123


Nell - October 3, 2023

Same question as above. This really seems like an important issue that TB should resolve!

Joseph Rigdon - March 8, 2023

Given that the Synapse 29/19 frames are retired, will there be some sort of replacement for these?

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