Bikepacking Seat Pack Evolution + 3 Seat Bags Compared
A look at the history and evolution of bikepacking seat bags and a comparative review of the Revelate Terrapin, Porcelain Rocket Mr. Fusion, and Bedrock Coconino… plus a sneak peak at the all new Mr. Fusion dry bag system.
For those unfamiliar, the seat pack is that curious stuffed missile that get’s strapped under the saddle at the rear of the bike. Its placement is inspired by traditional saddle bags, such as the classic canvas designs by Carradice, but the seat pack is designed for more rugged use and its structure is a bit more streamlined as a result. This was a revolution to ultralight multi-day mountain bikers who are able replace the typical below-the-saddle tool bag and carry much more gear in a way that’s significantly lighter and more aerodynamic than traditional panniers.
For those who are familiar with this piece of gear, the Viscacha, by Revelate Designs, might come to mind as one of the originals. According to Revelate’s Eric Parsons, “Jeff Boatman and I were the only people making bags back then. Who was first to make bikepacking seat bags – Jeff, he started in 2006 I believe, I started in 2007. I was doing my own thing in AK influenced by the needs of winter bikepacking races and got pulled into modern bikepacking later due to the rise of the Colorado Trail Race and the Tour Divide.”
The seat bag has progressed quite a bit since 2007. Designs changed in size to meet riders’ needs, and now there are a few unique systems out which allow the bag to quickly disengage from its harness, making packing and unpacking much easier. Here are three bags we’ve tested that push the seat pack in new directions:
The Bedrock Coconino & RailWing
The Bedrock Coconino with RailWing was conceptualized by and designed in collaboration with Joey Ernst from Velorution Cycles. The goal was to create an incredibly stable seat bag that can be removed from or loaded back on the bike in less than a few seconds.
The RailWing is a simple machined aluminum bracket that clamps onto the saddle rails. The intent of the RailWing is twofold, the first of which is to prevent ‘tail-wag’, which is the phenomenon that comes from pedaling with a large seat pack load, resulting in the bag swaying in a back and forth motion. The second is to enable the quick release of the bag for packing and unpacking.
The bag has a roll-top enclosure and a velco strap that secures it to the seatpost. The RailWing has two locking compression straps that affix to the bag. One perk of the RailWing is that there is not much that could bend or break in a crash; it’s a solid piece of metal. And the Coconino can function with or without the RailWing so you are never dependent on any hardware.
Let it be known that we haven’t taken the Coconino to the ends of the earth and put it through rigorous testing, but on initial rides and use, it’s an impressive and well-built seat bag with nice details such as locking compression clips. The main body of the bag is made from quality materials such as X-pac, and more durable heavy gauge fabric at the contact points. The RailWing is an interesting innovation that noticeably stabilizes the bag and serves as a very handy quick release and loading mount. It should be noted that the RailWing can also be retrofitted to work with the Revelate Viscacha or Pica.
Porcelain Rocket Mr. Fusion Seat Pack
The Mr. Fusion is Porcelain Rockets’s solution to ‘tail wag’. The system combines the stability of a traditional rack with a low profile design, modular harness system, and modern materials. Think internal frame backpack. The system has three parts: the rack with fabric harness, the upper harness piece with top clips, and the bag itself. The rack attaches to the seatpost via a custom machined aluminum collar. The bag has a roll-top enclosure and a velcro loop that lashes to the seatpost for added support. Two compression straps hug the sides and a single compression strap battens down the rear of the bag. With the rigid rack and the well designed compression points, there is absolutely no movement in the system, even on the rough stuff.
Obvious benefits of the Mr. Fusion system include its rock solid stability, the ease of removing the bag for packing, and the ability to customize your bag from an array of colors and fabrics. A couple of hidden perks are the ability to utilize the rack to lash on additional items, such as a spare tube, or a tent ground sheet.
Mr. Fusion V2
Version two of the Mr. Fusion (pre-production model shown above and below) features a radio frequency welded (RF) drybag and a slightly tweaked harness. The rack is the same but the upper harness is slightly different with internal panels which serve to stabilize and contain the load. Porcelain Rocket hopes to have the production sequel ready by late-August and it will retail for $185.
The Revelate Terrapin Seat Bag
The Terrapin by Revelate Designs is a holster-like mount that accepts the Revelate drybag or similarly shaped load. With the Revelate dry bag, the system is 100% waterproof and the bag can be quickly removed from the bike for ‘in the tent’ packing or unpacking. Out of all of the seat packs explored in this review, this one has gotten the most use.
The key to the Terrapin is it’s compression system and internal structure. It features a stiff plastic bottom and side sheets which helps lessen, although doesn’t completely eliminate, sway. The fiberglass stiffened sides prevent outward bulging with an unwieldy load. The lower compression straps feature an upward pull which engages the side panels, yielding an intricate compression that perfectly secures and shapes the load within the harness. The rear compression strap loops around a sturdy red loop and allows maximum lateral compression.
Out of all of the seat packs tested here, the Terrapin is the easiest to access and remove the bag. It also has an added benefit of allowing additional items, such as a tyvek ground cloth, to be nestled within the harness. Another impressive feature is the rugged design of the seat rail attachment (shown above in the middle photo).
The weight difference of these systems is fairly negligible, in my opinion. Here are the manufacturers’ claimed weights:
- Bedrock Coconino 14.6 oz / 414 grams
- Revelate Terrapin 17.5 oz / 496 grams (w/Drybag)
- Mr. Fusion 13 oz / 369 grams
Carrying capacity and size
All of these bags are adjustable and can be overstuffed, or rolled and cinched for a small load. The Terrapin is slightly larger capacity than the others, and the Coconino is the must streamlined with a tapered front that might be preferred by some who complain of thigh rub.
- Bedrock Coconino 6-12 liters
- Revelate Terrapin Up to 14 liters
- Mr. Fusion 5-13 liters
- Bedrock Coconino $175
- Revelate Terrapin $125 (w/drybag)
- Mr. Fusion $175
Which bag is our top choice, you might ask? Well, all three are excellent options (or else they wouldn’t be here); each has its particular strength and is fit for specific conditions. The Bedrock Coconino is a solid choice for those looking to travel light and fast. It has the most streamlined design and might also be a good fit for smaller riders who have limited space between the saddle and rear tire. The Revelate Terrapin is the least expensive and as of right now, the only one available that’s fully waterproof. It’s also the largest, and in my opinion the easiest to use with regard of removing and reinserting the bag. The Mr. Fusion is an excellent choice for long term expedition travel where rugged dirt roads and trails are the preferred terrain and sway is a concern. It is by far the most stable and also has the option to use the rack for additional storage. The version two production model will be fully waterproof as well.
While all three of these seat packs are incredible, my guess is that we’ll see even more innovations as bikepacking progresses. Stay tuned.
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