Surly Pack Rat Geometry & Bikepacking Bag Fit
Discontinued. Surly no longer lists the Pack Rat. It's here because these frames stay in circulation second-hand and the geometry is still what you need to pick bags — but you won't find one new.
Surly Pack Rat frame geometry, drawn to scale
Every tube angle and length below is from the published chart, not an illustration. The front triangle area is the number that decides which frame bags fit — and it changes a lot across sizes.
What this frame gives a loaded bike
Chainstay length is the gap between the seat tube and the rear axle, which a rack, panniers and your heels all have to share. Bottom bracket drop is how far the cranks sit below the axles. Both are compared against the median across every current frame we hold.
410-415mm chainstays, 22.5mm shorter than the 435mm median across the 65 current frames here. Bottom bracket drop 45-55mm, 20mm less than the 70mm median. The fork publishes cargo mounts, and the frame publishes up to 3 bottle or accessory positions. A rear rack bolts straight on.
Every figure above is the manufacturer's, computed against the rest of the database. It says what the frame allows, not how it feels — nobody here has ridden it.
What it can carry
Mount provision and clearance, as Surly publishes it.
Geometry
All figures in millimeters except angles. Effective top tube and seat tube are the two that decide frame bag fit.
| Size | Eff. top tube | Seat tube | Standover | Head tube | Stack | Reach | Chainstay | Wheelbase | BB drop | Head angle | Seat angle |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 38cm | 495 | 380 | 698 | 90 | 479 | 371 | 410 | 962 | 45 | 72.5° | 75.5° |
| 42cm | 505 | 420 | 725 | 105 | 495 | 372 | 410 | 963 | 45 | 73° | 75° |
| 46cm | 520 | 460 | 751 | 120 | 512 | 378 | 410 | 965 | 45 | 74° | 74.5° |
| 50cm | 535 | 500 | 777 | 135 | 527 | 384 | 410 | 975 | 45 | 74° | 74° |
| 52cm | 550 | 520 | 805 | 130 | 551 | 387 | 415 | 986 | 55 | 74° | 73.5° |
| 54cm | 565 | 540 | 821 | 145 | 566 | 392 | 415 | 996 | 55 | 74° | 73° |
| 56cm | 580 | 560 | 837 | 160 | 580 | 397 | 415 | 1005 | 55 | 74° | 72.5° |
| 58cm | 595 | 580 | 854 | 175 | 595 | 402 | 415 | 1014 | 55 | 74° | 72° |
Bottom bracket height
Roughly 320–330mm off the ground. Surly doesn't publish this directly — we derive it from their BB drop and a typical 75cm tire diameter, so treat it as indicative rather than exact. It changes with the tire you fit. Lower means more stable and more pedal strikes; higher means the opposite.
Source — Surly's own geometry chart: https://surlybikes.com/products/pack-rat — checked 2026-08-16. A dash means the figure isn't published; we leave it blank rather than estimate.
Questions people ask about this frame
Answered from what Surly publish. Where they publish nothing, that is what it says.
Does the Pack Rat take fork cargo cages?
Yes. Surly publish cargo-cage mounts on the fork, but the maker confirms mounts but does not publish how many, so we're not going to put a number on it.
What is the widest tyre the Pack Rat takes?
Not published in a form we can read. Surly don't publish a maximum tyre width for this frame.
Will a seat pack work on the Pack Rat?
Not published. Surly don't state dropper compatibility for this frame, so we can't tell you whether a dropper would compete with a seat pack on it.
Which frame bags fit
Every frame bag we track, checked against this frame's published geometry. Pick your size.
Checking 16 frame bags against a 550mm effective top tube and 520mm seat tube. 16 fit.
Frame bag fit is calculated from Surly's published geometry, so it's as reliable as their chart. Seat packs and handlebar rolls depend on your exposed seatpost and bar width, which no geometry table lists — the bag finder covers those once you add your own measurements.