Frame Bags – Product Design Notes

Over the past three years, we have been on a serious quest to build the best frame bags in the business. The resulting nine-model range is a culmination of experience, innovative sizing methods, and a determination to make a frame bag that will work for everyone.

Comprising nine unique half-frame and wedge-style models, as with any Tailfin product, the key emphasis is to provide the majority of riders, regardless of frame size, with options to fit. We are aiming the first range mainly at drop-bar riders, with dimensions optimised for narrower Q-factors associated with road and gravel bikes.

Tailfin Frame Bag product page

Framing the challenge

The frame bag is the heart of any complete bikepacking setup, and for a very long time, it has been our goal to create the best-performing frame bag in existence. While there are already some highly-regarded frame bags on the market, many of which do a great job of resolving one or more of the issues usually associated with this style of luggage carrier, we felt that none answer all of the problems currently faced by riders. During our research, we found that the fundamental issues riders have with existing frame bags can be broken down into:

• Production frame bags, often with only a few size options, can be a poor fit; most people don’t want to wait (or pay) for custom.
• Most frame packs don’t have a great deal of structure, so easily balloon and cause knee rub.
• The lack of structure in packs causes pinch points with the zip that leads to it bursting.
• Most are attached with velcro, which can either wear bib shorts, skin or cause frame damage.
• Most zips either require a bulky (knee-rubbing) rain flap or are not waterproof.
• ‘Map pockets’ cannot take bulkier items like pumps
• Frame bags and top tube bags usually require separate straps or clash, looking for a very untidy aesthetic
• Many frame bags require mounting on three sides of the pack, which again limits sizing
• If a frame pack isn’t well supported, it can require two hands to open and close the zip, limiting use while riding.
• Often, there is a lack of organisation inside.

Our Process

Our journey to the culmination of the frame bag project began with a truly innovative approach to data collection. After trawling various bike shops and brand websites, we realised that collecting the correct frame data would be critical to success. In order to do this, we engaged our customer database and asked riders to send us specific photographs of their current bike setup, complete with set data capture measurements.

Over five hundred riders participated and sent us their setups. To make sense of all this information, one of our design engineers wrote a custom piece of software to turn the images into a range of heat maps. These heat maps provided the baseline for our sizing approach.

It very quickly became apparent that opting for just a small number of sizes would not enable us to achieve the Tailfin Universal Fit approach found with most of our current products. It was going to need more, a lot more. After much agonising, we settled on the nine sizes released first: six Half-frame bags and three Wedge-shaped. With these nine frame bags, we are satisfied that the majority of riders, from riders of XS frames up to XXL frame sizes, could find at least one bag that would fit perfectly.

Why different shapes?

During our research, we also asked riders to indicate their water bottle preferences in terms of the number of bottles carried and preferred volumes. As expected, we realised that no single shape would work for all riders. This is why we wanted to offer riders the option to choose their frame bag based on whether they prefer to prioritise storage capacity or maximum water carrying ability, e.g. for a hot weather trip vs. cold weather. Of course, you could always size up or down to get to your preferred frame bag size, but offering a truncated wedge-style bag allows riders to fit a larger bottle on the seat tube. 

Additional fit considerations – no two frames are the same.

Just producing multiple sizes and hoping for the best is simply not the Tailfin way, so there are numerous additional features that enable our bags to fit seamlessly into the majority of frame sizes and shapes. The key here is that although the bags feature obvious structure, there is inbuilt conformity at the front and rear to accommodate different frame designs and internal frame geometry. 

Minimising knee rub – the secret is carbon.

We identified early on that one of the worst traits of existing frame bags was the tendency to bulge when overfilled, widening the bag and interfering with the rider’s leg whilst pedalling. This interaction is annoying at its best, but at its worst, it can lead to repetitive, ride-ending injuries. We knew we needed to add structure to the bags to reduce this bulging, but if we added too much stiffness, we’d limit the effectiveness of the storage space and access to your kit. Our solution was to create a carbon fibre space frame that produces a semi-rigid structure along the upper edges of the pack and below the zip. This carbon space frame gives the pack structure and the ability to resist ballooning.

We soon found, however, that using carbon of the same thickness across all sizes simply didn’t work. It was too stiff, the rods limited the ease of entry on smaller sizes, and it didn’t provide enough support for the largest bags. Determining the optimum thickness for the carbon across all nine sizes was one of the reasons why getting to this endpoint has taken so long! Taking our time to develop optimal carbon stiffness has resulted in comparable levels of lateral stiffness and ease of entry regardless of the bag size.

One additional point to note is that the carbon strips are user accessible and removable, so if you never suffer from knee rub and prefer to over-stuff a bag, you have the choice.

Another feature is, as with our Top Tube Bag range, the full range of Frame Bags features 3D shaping with a tapering design. This is mapped to follow the movement of the leg during pedalling, with the areas most at risk of interference benefitting from both a horizontal and vertical taper.

Zip durability

High on the list of issues many riders experience with their existing frame bag is a tendency for zip failures. This can be caused by overfilling the bag, pulling the zip out of alignment, lacking zip support in the structure, or simply dirt ingress. Our carbon struts and space frame structure help to reduce the chances of a zip bursting by supporting it, minimising pressure from content bulging or the pinch points where the velcro normally holds the pack. This support can be seen in the zip operation, which is now a true, one-handed technique with minimal restriction on zip movement.

We also carefully considered the size and style of zip we wanted to use. Simply opting for a YKK Aquaguard in the largest size was not possible given the size difference between the bags – a large zip would take up too much space, be too heavy and, quite frankly, look odd on the smaller Wedge bags. The zip size varies from Number 6 on the smallest bags up to Number 10 on the largest versions. The zip itself is a custom-sourced waterproof version that holds the teeth under tension whilst shut, creating the maximum amount of waterproofing with less chance of the teeth being exposed when under load.

We learnt a lot from using zips on our top tube bags, and one of the critical pieces of feedback we received was about unwanted noise from the zip puller. We always listen to feedback and aim to continuously improve, so for the frame bags, we developed a custom zip puller designed to eliminate noise and rattle*

*This design will be rolled into the next batch of Zipped Top Tube Bags

Construction

The Tailfin Frame Bag range features our high-frequency welded construction throughout and uses our signature Hypalon and Ripstop Nylon materials for the perfect blend of high durability, flexibility, and reduced weight. 

The internal Carbon Space Frame is designed to prevent the classic sagging that can occur between frame attachment points. Consisting of two lightweight carbon rods linking internally to the top V-Mounts. These add minimal weight but increase the pack’s longevity, support zip integrity and reduce stress on the V-Mount attachment points. 

The evolved V-Mount system

Our V-Mount attachment system is a simple but effective way to safely attach bags to your bike. Following the release of our Downtube Packs and then Top Tube Bags, this is the third outing of the V-Mount system, and with each product release, we are evolving it and improving for each use case. 

The V-Mount system combines many parts that work together in harmony: from the tacky rubber pads to the abrasion-resistant and grippy TPU straps, to the welded V-Mount tunnel/garage, to how we transfer the rigidity, to the internal structure of the frame bag. These V-Mounts form a robust structure capable of withstanding any knocks from the rider while remaining locked in place regardless of riding conditions and terrain. 

Most frame bags use velcro or other inherently unstable attachment methods that introduce a certain amount of movement to the pack whilst riding. This movement can damage the finish of your beloved bike, even when riding on dry and clean roads, and in some extreme cases, cause actual damage to the bike frame itself. When attached correctly, our V-Mount system with dedicated TPU straps stops movement completely. 

An important point to note is that the spacing of the front V-Mounts considers the positioning of the V-Mounts found in our range of Top Tube Bags. This allows for sharing straps, reducing weight and fit time whilst also providing a very clean look with as few straps as possible. 

Additional Features

Map pocket: The smaller, lower-volume side of a frame bag’s internal divider, known as a ‘map pocket,’ is often restricted in its capacity to accommodate deeper or larger-volume items. Our Frame Bag features an internal stretch mesh divider that enables bulkier items, such as pumps, to protrude inward into the main body of the pack rather than outward towards your legs.

Clear pack organisation: Internal pockets feature on both sides of the internal stretch mesh divider, including a zipped valuables pocket. We have also incorporated a lighter-coloured interior to make it easier to find your kit.

Hydration hose-compatible port: Providing an option to house a hydration bladder is useful for carrying more water. A wide opening at the front allows for a hose to pass through, so you can still access it on the go. This opening can also be used to pass cables from power banks to keep your tech fully charged.

Waterproof: Finally, as mentioned before, our welded construction and material choices have allowed us to create a fully waterproof frame bag, allowing you to keep your valuables and electronics safe and dry*

*Without over-packing the bag, and with the zip slider fully in the garage. Please note that the bag is not submersible.

Tailfin’s Frame Bag Sizing Tool

Finding the perfect fit: With so many sizes and styles to choose from, we wanted to ensure that riders could pick the optimum frame bag to suit their needs. We employed advanced methods to determine the optimal size of the frame bags and developed a machine learning-based tool to help riders determine and visualise the best Tailfin Frame Bag for their bike.

The Frame Bag Sizing Tool allows you to perfectly scale your bike, drag, rotate, and place our frame bags in the correct location so you can see which ones will work the best. The process is simple: you just need to take a photo of your bike from the correct distance and angle and upload it into the tool on our website. The software does the hard bit, and then you can go to town to find the best option.

Find the Frame Bag Sizing Tool here.