The Tailfin Rear Top Tube Bag comes in two sizes, one to suit road or gravel bikes, and one to suit mountain bikes. Designed to fill the gap in front of your seatpost with useful, waterproof storage, the bag will fit any bike and stays put. Be sure to choose the right version, to avoid thigh rub.
> Buy now: Tailfin Rear Top Tube Bag for £55 from Tailfin
As its name suggests, the Rear Top Tube Bag sits just in front of your seatpost, on the top tube. It’s secured by two straps around the top tube, and an optional third strap around the seatpost.
The base that contacts your top tube is slightly V-shaped and rubberised, with three slots to choose from to pass the provided rubber straps through. This allows you to pair the Top Tube Bag with other Tailfin bags inside your frame using the same straps. The straps are Tailfin’s take on the classic Voile strap, and are both tough and stretchy to get the fit right.
The construction is ‘3D-welded’ Hypalon fabrics, which I can vouch for as being very tough indeed. Being welded with a water-resistant zip, the bag is almost totally weatherproof, but not immersion-proof. Tailfin recommends sensitive electronics be placed in plastic bags.
On the front of the bag there’s a small round hole. This doesn’t vent inside the bag, rather it’s the zip ‘gutter’ outlet that allows water to drain from the zip garage to minimise the risk of any water ingress when opening the bag – nice.
Inside the interior is coloured white and light blue, making it easy to find small things. The base is padded to help protect and silence things that might bump around inside. Along the top of each side is a thin carbon fibre rod, which gives the bag considerable shape.
Spares include the rubber foot, straps and the interior padding, should something need a refresh.
A half-hour under the road.cc Kitchen Tap Of Doom resulted in exactly zero water ingress, the zip ‘gutter’ working exactly as designed to keep water out when opening the bag. This matters, as most top tubes will be sloping backwards, meaning a zip garage would fill and leak backwards into the bag on opening.
The 0.8L mountain bike bag is shorter than the road/gravel one at 124mm as opposed to 139mm, to accommodate dropper posts. The mountain bike one also has an 85-degree top tube/seatpost angle, whereas the road/gravel is 110 degrees. The mountain bike bag is 42mm wide at the top, widening out to 45mm at the bottom, against the road/gravel one that starts 36mm wide and increases to the same 45mm. This recognises the narrower Q-factor (ie pedal width) of road/gravel bikes vs mountain bikes.
That’s not to say you can’t mix and match across bikes with the one bag – and it might be you can run the mountain bike bag on a road/gravel bike just fine, or vice versa. Choices choices. Tailfin provides a downloadable printable sheet so you can see what will best fit your bike before ordering.
> Best bikepacking bags – how to choose lightweight luggage for cycling adventures
Weight-wise, both bags are within a few grams of each other, the road/gravel option coming in at 120g on the road.cc Scales of Truth including straps.
I found the wider mountain bike bag gave some slight thigh rub when fitted to my gravel bike, but not overly so. Everyone’s bike geometry, thigh clearance and clothing choice will differ, so there’s no guarantee of a perfect rub-free experience, but with the tapered design and reinforced sides, Tailfin has done its best to cater for a wide range of riders.
You can get a fair amount of stuff into 0.8 or 0.9L of bag – I was able to pack away a mini-pump, a 29 x 3in TPU tube, a multi-tool, two levers and a Dynaplug into either one with ease. In the road/gravel bag you’re able to fit a pump of around 200mm length diagonally.
In use, the Rear Top Tube bag is both stable and silent. The combination of rubberised mount and grippy straps makes for a very secure and silent attachment, with few concerns about paint damage. Although, as with strapping anything to your bike, if you are really worried use some tape underneath as fine grit will work its way into the smallest of gaps.
Talifin hasn’t added bolt-on capability, as few if any bikes have bag bolts at the rear of the top tube.
Value
Tailfin isn’t the first to think of using this space on a bike – Alpkit’s Fuel Pod Rear is £15 cheaper at £39.99, and a bit larger at 1L, but isn’t waterproof as it uses stitched not welded seams. At 95g it’s a smidge lighter than the Tailfin bag.
Yorkshire’s Restrap does a 0.8L Rear Top Tube Bag for £37.99. It goes from just 30mm to 50mm, so might better suit those looking for minimal rub risk. As Restrap puts the zip closed at the top there’s no need for an anti-pooling zip garage, and that also means stuff is less likely to fall out – not that I had any issues like that with the Tailfin bag. This bag is seriously light at nearly half the weight of the Tailfin offering – achieved by lacking a mount rubber foot and using much lighter Hypalon straps as opposed to rubber straps. Again, Restrap’s bag isn’t welded, so some leaking can be expected in heavy rain.
The closest competitor is Apidura’s Backcountry Rear Top Tube Pack at £54. Apidura uses a welded construction so waterproofness is better than Alpkit or Restrap, but the width is a constant 45mm, meaning rub is more likely. Apidura doesn’t do a road/gravel version, and the bag sits directly on the bike frame, held on with Velcro straps.
Tailfin offers a 30% discount on replacement gear that’s damaged in a crash, and a five-year warranty on manufacturing defects. Apidura, Alpkit and Restrap all offer lifetime warranties.
Conclusion
Overall, the Tailfin Rear Top Tube Bag continues the company’s dominance at the premium-priced end of high-performance bikepacking systems. The combination of waterproofness, rigidity, repairability and features adds up to justify the pretty hefty asking price.
> Buy now: Tailfin Rear Top Tube Bag for £55 from Tailfin
Verdict
Great option for keeping small things safe in an otherwise unused space on most bikes
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road.cc test report
Make and model: Tailfin Rear Top Tube Bag – Road/Gravel
Size tested: 0.9L
Tell us what the product is for and who it’s aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?
It’s for people wanting to carry tools, snacks or whatever in an otherwise unused space on their bikes.
Tailfin says: “This compact and carefully designed bag transforms the often-overlooked space in front of the seatpost into practical, accessible storage – keeping essentials within easy reach without causing interference. Featuring:
Rock-Solid Stability: Our next-generation ‘V-Mount’ attachment system eliminates movement even on rough terrain
No More Thigh Rub: Internal carbon battens prevent the bag from bulging outward
Highly Water-Resistant Design: Advanced materials and construction helps keep your essentials dry
Easy Access: Front-to-back zipper design means you can easily see and reach contents
Simple Cleaning: Removable shock-absorbing insole protects your gear and makes cleaning a breeze”
Tell us some more about the technical aspects of the product?
From Tailfin:
Road/Gravel
Weight
109g Mounted with 2 Straps
118g Mounted with 3 Straps
Volume
0.9L (Road/Gravel geometry)
MTB:
Weight
112g Mounted with 2 Straps
121g Mounted with 3 Straps
Volume
0.8L (MTB geometry)
Construction
210D Hypalon &
210D Diamond RipStop
Typical top-class Tailfin quality.
Silent, solid, and waterproof within reason (ie without being immersed).
The materials and build are very tough.
Heavier than alternatives, in one case nearly double.
It costs a little more than some but those are less waterproof; it’s £1 more than its closest competitor, but the Tailfin’s taper likely makes it a more comfortable option.
Tell us how the product performed overall when used for its designed purpose
It’s silent, solid, and waterproof within reason.
Tell us what you particularly liked about the product
The quality. And the zip ‘gutter’ outlet. Nice.
Tell us what you particularly disliked about the product
It hasn’t totally solved the risk of thigh rub.
How does the price compare to that of similar products in the market, including ones recently tested on road.cc?
Alpkit’s Fuel Pod Rear is £15 cheaper at £39.99, and a bit larger at 1L, but isn’t waterproof as it uses stitched not welded seams. At 95g it’s a smidge lighter than the Tailfin bag.
Yorkshire’s Restrap does a 0.8L Rear Top Tube Bag for £37.99. It widens from just 30mm at the top to 50mm, so might better suit those looking for minimal rub risk. This bag is seriously light at nearly half the weight of the Tailfin offering – achieved by lacking a mount rubber foot and using much lighter Hypalon straps as opposed to rubber straps. Again, Restrap’s bag isn’t welded, so some leaking can be expected in heavy rain.
The closest competitor is Apidura’s Backcountry Rear Top Tube Pack at £54. Apidura uses a welded construction so waterproofness is better than Alpkit or Restrap, but the width is a constant 45mm, meaning rub is more likely. Apidura doesn’t do a road/gravel version, and the bag sits directly on the bike frame, held on with Velcro straps.
Did you enjoy using the product? Yes
Would you consider buying the product? Yes
Would you recommend the product to a friend? Yes, with caveats.
Use this box to explain your overall score
It’s very good: superb quality, almost totally waterproof, and very stable. It’s on the heavy side, though, and hasn’t totally solved the risk of thigh rub.
About the tester
Age: 47 Height: 183cm Weight: 77kg
I usually ride: Sonder Camino Gravelaxe My best bike is: Nah bro that’s it
I’ve been riding for: Over 20 years I ride: A few times a week I would class myself as: Expert
I regularly do the following types of riding: cyclo cross, general fitness riding, mtb, G-R-A-V-E-L
2 thoughts on “Tailfin Rear Top Tube Bag”
Mike is this not thigh rub?
Mike is this not thigh rub?
A great percentage Us bikers have larger legs
Hey Freddy, I think I’ve
Hey Freddy, I think I’ve covered this in the review – yes, there’s a risk of rub, and a bag in this position will not work for everyone.