Revelate Designs Spinelock 16 Seat Bag vs Tailfin CargoPack Alloy
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, price and value per litre; the CargoPack Alloy takes capacity. The biggest single gap is $250 between them. 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
6 of the 6 things we can measure come out differently.
Capacity
2L more in the CargoPack AlloyThe 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
449g 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
$250 between themManufacturer's price as we hold it.
Per litre
$12.70 per litre between themPrice divided by the maker's capacity. A crude measure that still catches the case where the dearer bag is also the bigger one, which the price alone hides.
Side by side
Including the rows where they are level.
| Revelate Designs Spinelock 16 Seat Bag | Tailfin CargoPack Alloy | |
|---|---|---|
| Capacity | 16L | 18L |
| Reach behind the saddle | 50cm | 55cm |
| Depth | 22cm | 24cm |
| Weight | 680g | 1129g |
| Price | $170 | $420 |
| Per litre | $10.63 | $23.33 |
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