If you want to go bikepacking and use a mountain bike fitted with a dropper post, there are a few hurdles you often need to overcome. Straight Cut has designed this bag specifically for use with a dropper post when used with a specific adapter, and the performance it delivers is really good. The volume may sound quite limited, but I found it was enough for a full sleeping system, and the lower volume does help limit movement when riding.
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Straight Cut, based in Scotland make all their bags in-house. They also offer various custom bags, as well as a few standard options. The Dropper Seatpost saddlebag is a standard option, and the only off-the-shelf seat bag they offer.
The main fabrics used to construct the bag are 1000d Cordura and X-Pac, both chosen for their durability. The bag is relatively small, quoted as 4 litres, although it does seem a little larger than the claimed figure, especially when packed. Straight Cut said the volume is based on the size when correctly closed, which includes a minimum of three folds on the opening, but this may be different to how others measure the volume.
The size, volume, and shape provide the clearance you will need over the rear tyre when the seatpost is dropped. Straight Cut state a minimum of 150mm clearance is needed, which you can measure before purchasing, from the bottom of your seatpost to the tyre with the post fully down. What really helps with tyre clearance is the shape of the bag thanks to its long, extended rear and shallow depth.
The bag requires an adapter to use, with the Wolftooth Valais being a popular option. This is available to buy with the Straight Cut bag, which will cost an extra £25. The adapter provides extra width to the post, allowing the bag to be strapped securely. The Wolftooth Valais will reduce the travel on your post by a minimum of 25mm, depending on how low it is mounted.
The bag is secured with straps over each saddle rail, plus a long strap that goes over the opening area and secures near the back of the saddle. Each strap has a lock, which ensures there is no slip within the straps when riding. There is a single velcro strap around the seatpost, at the exact width of the Valais adapter, and while the strap itself is quite narrow, the area of velcro on the bag to is wider, which makes fixing a little easier.
Despite being quite small in volume, I found the size of the opening sufficient to pack in all my sleeping kit, fitting a bag, mat, bivvy bag and pillow without issue. The rear opening has a plastic strip on the bottom edge, which might seem like a small addition, but this really helps when folding and closing the bag neatly and holding its shape. The bag itself weighed 263g, and with my kit fully packed it was 928g. This is very light, but packing high volume, low-weight items of kit will reduce the amount of movement when riding.
It would be fair to expect mountain bikes to take on rougher, more technical terrain than gravel or road bikes, and you might expect this to result in more movement. In use, even on some really rough descents, there was no noticeable sideways sway, and this was also true when climbing out of the saddle. A combination of the solid straps to secure it, and keeping the bag quite light are key factors, as well as the shape and design.
It has been very dry recently, making it tougher to test the water resistance while riding, but it didn’t suffer any leaks when out riding, or when testing in a much tougher situation with a hosepipe blasted at it for several minutes at all angles, so I am confident it will stay dry through even the most torrential weather.
What makes the Straight Cut bag stand out are the small touches that show its quality. The internal shims that help hold the shape and make packing easier, bar-tacking at all attachment points, the wider velcro attachment point, locking buckles, and the plastic strip to aid packing. It all adds up to create a solid bag that feels like it will stand up to the toughest riding. If there is one feature I would have liked, it is the ability to lace up an elastic cord on the top, as I find this useful for storing something like a waterproof jacket that you might need really quick access to. The limited size of the bag might be the main factor, but it is a feature that some other bags have.
At £150 without an adapter, it isn’t cheap, plus there are cheaper options available. Apidura did have a version specifically for dropper posts, but the Backcountry model is compatible and is available in 4.5 or 6-litre options. The comparable 4.5-litre size costs £118 without an adapter or £140 with its own adapter, and the claimed weight of the bag is a touch lower at 235g. Miss Grape also produces the Cluster 7, offering 7 litres of space with a similar design that costs €153 without an adapter, but while that is claimed to be much larger, I doubt there is actually 55% more space.
It is an expensive bag, and that can’t be ignored, but it also feels incredibly well-made, as have all the other Straight Cut bags we have tested. The smaller touches go further than just the materials and shape to create a bag that stands out at the top, both in design and construction.
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Product purpose:
The dropper seatpost saddlebag is an aerodynamic storage solution compatible with the Wolftooth® Valais dropper seat post clamp. Designed, tested and pushed to its limits over four years we are confident this is the ultimate bikepacking essential. Constructed using water-resistant materials with minimal water ingress points the design has a contoured profile with reinforced side panels. An internal HDPE shim keeps it neatly attached below your saddle and clear of your legs while riding. The triple point attachment design utilises the saddle rails and seat post collar keeping it secure. The bag features a rear roll-top closure with a secure cam buckle compression strap allowing you to cinch tight.
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Specifications –
Dimensions – L:330 x H:120
Capacity – 4.5L
Weight – 265g (without Wolftooth® Valais)
Made from durable water-resistant 1000d Cordura® and waterproof X-Pac® fabrics
Liner made from bright orange nylon
Internal HDPE plastic shim to hold the shape on base and side panels
Solid 3-point attachment – Pair of compression saddle rail and seatpost compression straps
Designed with minimal seams to achieve high water resistance
Designed to work with the Wolftooth® Valais seatpost collar
Bar-tacked at all attachment points for strength
Compatible with tyre/seat post clearance of 150mm or above.
Closure – The bag should have the rear opening rolled 3 times minimum to be securely closed.
Tyre Clearance – To ensure your tyre won’t rub the bag please check the clearance between the tyre and your seat at its lowest position. Please account for movement from the rear suspension. Measure from the centre top of your seat post to the closest edge of the tyre – Compatible with tyre/seatpost clearance of 150mm or above.
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