Revelate Designs Spinelock 16 Seat Bag vs Tailfin Alloy Seat Pack
Two seat packs, measured against each other on the figures that decide whether they work on a bike.
The short answer
The Spinelock 16 Seat Bag takes how far it reaches back, tire clearance, weight and price; the Alloy Seat Pack takes capacity. Which of those you care about depends on the frame you are fitting it to.
Assembled from the differences below rather than written over them. Every figure is a published measurement or computed from one — nobody here has used either one.
Where they differ
5 of the 6 things we can measure come out differently.
Capacity
4L more in the Alloy Seat PackThe maker's own figure. Worth reading alongside the dimensions below rather than on its own — two bags of the same litreage can want very different frames.
Reach behind the saddle
5cm shorter on the Spinelock 16 Seat BagLength is the lever arm on the seatpost, and the longer lever is what makes a loaded pack sway. Shorter is easier to live with; longer usually means more volume. It is a trade, not a fault.
Depth
2cm shallower on the Spinelock 16 Seat BagDepth is what competes with the rear tire once the pack sags under load. On a small frame or a big tire this is the measurement that decides it.
Weight
125g lighter on the Spinelock 16 Seat BagEmpty weight as published. Worth holding against capacity rather than alone — the lighter bag is not the better one if it carries a third less.
Price
$55 between themManufacturer's price as we hold it.
Side by side
Including the rows where they are level.
| Revelate Designs Spinelock 16 Seat Bag | Tailfin Alloy Seat Pack | |
|---|---|---|
| Capacity | 16L | 20L |
| Reach behind the saddle | 50cm | 55cm |
| Depth | 22cm | 24cm |
| Weight | 395g | 520g |
| Price | $170 | $225 |
| Per litre | $10.63 | $11.25 |