Ortlieb’s seat pack shares the same fully waterproof construction as its handlebar roll. A combination of polyurethane ripstop nylon joined with Ortlieb’s top secret Radio Frequency Welding tech means stitch-free seams and less opportunity for water ingress. Like the handlebar roll, Ortlieb has opted for a single unit construction over a separate dry bag and cradle.
Attaching the pack to your bike couldn't be simpler thanks to a pair of heavy duty velcro straps, which anchor the bag to the seatpost, and to hold it up a pair of clipped webbing straps loop through the saddle rails and run to the base of the pack. The clips have a sliding buckle and lockable clip to make sure things stay put when the going gets rough.
The velcro straps are bolted through a formed plastic frame, which aides in making a stable base for the bag and shapes the bag into a tapering wedge. With the thin edge of the wedge below the saddle we didn’t get any thigh rub, even when loaded to the gills. It does however take up a lot of seatpost height so unless you run a long post you may find you run out of room for it.
This isn't the most stable seat pack we have used, a problem that is possibly confounded by its size and the weight of the huge payload it can carry. We noticed quite a bit of side sway at times, especially in techy and rocky descents.
The biggest problem we had was when running it on our full suspension test rig (Rocky Mountain Sherpa) where the size of the bag meant there was often rub between tyre and pack when the going got tough — even when the suspension was locked out. However this definitely isn't an issue when used on any rigid bike.
Ortlieb’s attention to detail is excellent, with shock cord webbing on the top of the bag, reflective patches for low-light visibility and multiple fix points for attaching a rear light even when the bag is very full. The standout feature has to be the purge valve, which allows for easy rolling of the roll top dry bag as it releases air as you roll — removing the need for fiddly burping of excess air.
Ortlieb’s cavernous seat pack is ideal for long expeditions, but is probably overkill for most overnight adventures. While it won't appeal to die-hard ultralight geeks, the rugged construction and full waterproofing will suit most riders.
We advise careful checking if you are planning on using on a full suspension bike or if you don't run a terribly long seat post. We hope that a smaller version is in the pipeline for shorter trips.