BackLoader 15L
Where to Buy
How much room does it need?
This pack measures 67cm long and 28cm deep. Length is how far it reaches behind your saddle, and it's what drives sway — a long pack is a longer lever on the seatpost. Depth is what competes with your rear tire once the pack sags under load.
Across the 17 seat packs we hold dimensions for — which run from 31.8cm to 67cm — this one reaches further back than 16 of them, and hangs deeper than 16.
The other number that decides this — how much seatpost you have showing above the collar — depends on your leg length rather than your frame, and makers almost never publish a minimum. So measure from the top of your seat collar to the bottom of your saddle rails, then check it against the mounting hardware on the product page. If you run a dropper post, look for a pack that mounts to the saddle rails alone.
Check against your measurementsTopeak BackLoader 15L— Specs & Analysis
Manufacturer specifications, compared against every other seat bags in our database. We do not test gear in the field — we measure, verify, and compare.
Fifteen liters and 67cm of it. The BackLoader 15L is the longest seat pack in our entire dimension database — 18cm longer than the category median — and that length is the whole story, good and bad.
A 67cm seat pack is a serious object. For context, the median seat pack in our database is 48cm long and the next longest is 55cm. This thing extends well past what most riders have room for.
That buys you 15 liters, which is a sleeping bag and a shelter and then some. It also means two things you need to check before you buy. First, tire clearance: a long pack that sags is a pack that rubs, and 15 liters of load on a 67cm lever arm generates real sway. Topeak publishes an L1/L2 minimum-clearance diagram for exactly this reason. Second, exposed seatpost — you need enough post showing to mount it, and riders on small frames or long-legged riders on compact frames frequently don't have it.
The construction is a water-repellent outer over a 10,000mm waterproof inner bag, which is the right way round: the inner keeps your sleeping bag dry, the outer takes the abuse. 28cm tall and 18cm wide when loaded.
565g is not light, and the air-release valve and mounting hardware are where it goes. If you're chasing grams there are 400g options at similar volume. If you want a big, cheap, well-supported pack from a brand your local shop stocks, this is that.
Who Is the Topeak BackLoader 15L Best For?
Riders with tall frames and plenty of exposed seatpost who need maximum seat pack volume on a budget. If that describes your riding style, the BackLoader 15L should be at the top of your shortlist. It sits in the Seat Bags category alongside 17other products we've reviewed.
How It Compares
At 565g and $123, the BackLoader 15L is 423g heavier than the lightest option in this category (the Revelate Designs ECOPAK Shrew Seat Bag at 142g). The most budget-friendly option is the Topeak BackLoader 10L at $70.
The price-to-weight ratio comes in at $22 per 100g — a reasonable middle ground between performance and value.
What We Like
- +15L is genuinely enough for a sleeping bag and shelter
- +10,000mm waterproof inner bag protects the load properly
- +Widely stocked — easy to replace parts and buckles
Watch Out For
- −67cm is the longest seat pack we hold dimensions for — clearance is a real question
- −565g is heavy for the volume
- −Long packs sway; check Topeak's clearance diagram before you buy
The Bottom Line
We haven't scored the Topeak BackLoader 15Lyet. It's here for its verified specifications and dimensions, which is what the fit tools run on — a score is an editorial judgement and we don't hand one out until someone has a basis for it.
Specifications and dimensions come from the sources listed above. Where a page draws on first-hand riding, it says so.
How it compares
Against the 18 seat bags we hold published specs for.
At 565g the BackLoader 15L is lighter than 3 of 17 alternatives we track, which makes it among the heaviest we track. The category median is 428g.
At $123 it undercuts 13 of 17 of them, against a median of $158. That works out at $22 per 100g — below the $39 median for seat bags.
Weight and price come from published specifications. Cost per 100g is a blunt measure — it rewards light gear and says nothing about durability or whether the thing works — so treat it as one input, not a verdict.
More in Seat Bags
Seat bags extend behind the saddle, carrying gear without the need for a rear rack.