Tailfin Rear Top Tube Bag: Unexpected Brilliance

Earlier this spring, I purchased a Santa Cruz Blur Trail frame and built up a downcountry rig that has quickly turned into my all-time favourite bike. On an average ride, I only carry the essentials. I pack a multi-tool, tire plugs, tube, and CO2. I typically carry a couple of snacks—anything from Skittles gummies to Clif bars. Depending on my ride plan and weather, I'll often add a rain jacket or vest. On my gravel bike, this is all stored conveniently in my frame bag. On my mountain bike, I carry a small seat pack with my repair kit, and until recently, I'd stuff the rest of it into my pockets.

When Tailfin delivered the Aeropack Cargo for review, they also sent their soon-to-be-released Rear Top Tube Bag. I initially overlooked it and left it parked in my gear closet. On first assessment, it looked too small to add any meaningful storage to my bikepacking setups; however, I didn't consider it for my mountain bike.

The Problem: Downcountry Distance

Brendan Leonard, the author behind Semi-Rad, hypothesizes that almost all of his friends are either uphill people or downhill people. After years on a downhill-minded trail bike, building up my downcountry bike has confirmed what I've always known. I am an uphill person.

Since buying the Blur Trail, my average rides have grown from 15-20 km to 30-40 km. I've ridden stages of the BC Bike Race course, linked together many of Cumberland's best trails, and opted for the mountain bike over my gravel bike on some longer, rougher gravel routes.

The longer my rides become, the more difficult it is to carry the minimum essentials in my small seat pack and jersey pockets. I've tried using my Apidura Racing Hydration Vest and a hip belt, but I would prefer to add weight to the bike rather than the body whenever possible.

An Obvious Solution: Tailfin Rear Top Tube Bag

When an invitation to scout the BC Bike Race Stage 6 route in Campbell River's Snowden Demonstration Forest trails coincided with a particularly hot day, I installed the Tailfin Rear Top Tube bag on my Blur Trail. It was the only way I could carry enough fuel of my favourite candy, gels, and electrolytes to get through the ride without adding the unwanted warm hydration vest.

The bag was quick to install. It has two straps that fit around the top tube and hold it securely. I added a third strap, around the seat tube; however, it would subsequently prove unnecessary on upcoming rides.

Tailfin has always been a premier bikepacking gear maker, and this bag is no exception. It feels equally durable to the Tailfin craftsmanship I've appreciated on the kit I've been using for years. They did create two versions of this bag: 0.9L for road/gravel bikes and 0.8L for mountain bikes, both for $80 USD. The differences are subtle, but the shape appears adapted for the slight difference in geometry to make a more secure fit. For anyone already using a Tailfin frame bag, the mounting system integrates seamlessly, too, adding extra storage without additional straps.

I already own a few Tailfin Top Tube Bags, and I can't remember the last time I went for a ride without one installed on my gravel bike. But I rarely use one on my mountain bike, and it's not just the aesthetic. I've always felt they get in the way on technical terrain. I frequently bump my knees into them on technical terrain when climbing out of the saddle.

With the rear top tube bag, I added nearly 1L of storage to my mountain bike in an innocuous way. The bag tucks firmly against the seat tube and top tube junction, and it doesn't move. With the wider Q factor on mountain bikes, it's virtually impossible to brush my knees against the bag when clipped in. It's so streamlined that the bag can virtually hide behind the seat tube.

The 0.8L size holds the essentials without adding unwanted weight to the bike. I've packed mine with enough snacks to fuel a 5-hour ride. It also fits a size L Rapha Anorak Rain Jacket, or a substantial repair kit. Even when packed to its limits, it stays narrow and doesn't bulge. The zipper works smoothly, too, making for easy one-handed access when riding.

When attempting to swap the bag onto my wife's Blur Trail, we did discover a small issue. Her medium-sized frame, paired with a 170mm dropper, doesn't leave enough clearance for the bag. When the post is lowered, the saddle hits the bag. On my XL frame size, this wouldn't be an issue even if I were running a much longer dropper, but this is a limitation to consider.

Wrap Up

I can't pretend the Rear Top Tube Bag is a revolutionary product; top tube bags have been a staple of my bikepacking setup since I first discovered the sport. Like many Tailfin products, they simply took an existing product and reimagined it. The refined version fits a niche perfectly and provides some much-needed storage in a very streamlined way.

While it might not be an innovative new product, the Rear Top Tube Bag is unexpectedly brilliant. It offers the same storage as a standard top tube bag, but it's tucked neatly out of the way. I rarely notice it while riding.

Since that first ride in Campbell River, the rear top tube bag has never left my bike. After more than a dozen rides in a variety of terrain, its function still surprises me.