Revelate Designs Terrapin System 8L vs Topeak BackLoader 10L
Two seat packs, measured against each other on the figures that decide whether they work on a bike.
The short answer
The Terrapin System 8L takes how far it reaches back and tire clearance; the BackLoader 10L takes capacity, weight, price and value per litre. 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 BackLoader 10LThe 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
6.8cm shorter on the Terrapin System 8LLength 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
6.8cm shallower on the Terrapin System 8LDepth 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
52g lighter on the BackLoader 10LEmpty 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
$139 between themManufacturer's price as we hold it.
Per litre
$19.13 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 Terrapin System 8L | Topeak BackLoader 10L | |
|---|---|---|
| Capacity | 8L | 10L |
| Reach behind the saddle | 43.2cm | 50cm |
| Depth | 15.2cm | 22cm |
| Weight | 482g | 430g |
| Price | $209 | $70 |
| Per litre | $26.13 | $7.00 |