Surly

Surly Midnight SpecialGeometry & Bikepacking Bag Fit

Frame
4130 Chromoly steel
Wheel size
650b
Max tyre
27.5 x 2.35 in or 700c x 42mm without fenders
From
$2,349
Sizes
8

Surly Midnight Special 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.

Surly Midnight Special — 40cm. Front triangle ≈ 969 cm² · effective top tube 500mm · seat tube 400mm
Surly Midnight Special in size 40cm, drawn to scale from Surly's published geometry. The shaded area is the front triangle — roughly 969 cm² of space for a frame bag. Wheels are indicative; frame lines are accurate.
Surly Midnight Special — 46cm. Front triangle ≈ 1150 cm² · effective top tube 520mm · seat tube 460mm
Surly Midnight Special in size 46cm, drawn to scale from Surly's published geometry. The shaded area is the front triangle — roughly 1150 cm² of space for a frame bag. Wheels are indicative; frame lines are accurate.
Surly Midnight Special — 50cm. Front triangle ≈ 1295 cm² · effective top tube 540mm · seat tube 500mm
Surly Midnight Special in size 50cm, drawn to scale from Surly's published geometry. The shaded area is the front triangle — roughly 1295 cm² of space for a frame bag. Wheels are indicative; frame lines are accurate.
Surly Midnight Special — 54cm. Front triangle ≈ 1436 cm² · effective top tube 555mm · seat tube 540mm
Surly Midnight Special in size 54cm, drawn to scale from Surly's published geometry. The shaded area is the front triangle — roughly 1436 cm² of space for a frame bag. Wheels are indicative; frame lines are accurate.
Surly Midnight Special — 56cm. Front triangle ≈ 1527 cm² · effective top tube 570mm · seat tube 560mm
Surly Midnight Special in size 56cm, drawn to scale from Surly's published geometry. The shaded area is the front triangle — roughly 1527 cm² of space for a frame bag. Wheels are indicative; frame lines are accurate.
Surly Midnight Special — 58cm. Front triangle ≈ 1623 cm² · effective top tube 585mm · seat tube 580mm
Surly Midnight Special in size 58cm, drawn to scale from Surly's published geometry. The shaded area is the front triangle — roughly 1623 cm² of space for a frame bag. Wheels are indicative; frame lines are accurate.
Surly Midnight Special — 60cm. Front triangle ≈ 1730 cm² · effective top tube 605mm · seat tube 600mm
Surly Midnight Special in size 60cm, drawn to scale from Surly's published geometry. The shaded area is the front triangle — roughly 1730 cm² of space for a frame bag. Wheels are indicative; frame lines are accurate.
Surly Midnight Special — 64cm. Front triangle ≈ 1908 cm² · effective top tube 625mm · seat tube 640mm
Surly Midnight Special in size 64cm, drawn to scale from Surly's published geometry. The shaded area is the front triangle — roughly 1908 cm² of space for a frame bag. Wheels are indicative; frame lines are accurate.

How it rides loaded

425mm chainstays and 65-70mm BB drop keep the bike compact and road-oriented; three bottle mounts and fork rack mounts support light loads, but no dropper routing or fork Three-Pack mounts are published.

Drawn from the published geometry and mount spec above, not from reputation.

What it can carry

Mount provision and clearance, as Surly publishes it.

Fork mounts
Upper, lower, and mid-blade rack mounts
Bottle mounts
3 standard
Rack & fender
Fork rack mounts and fender mounts published; rear rack mounts not separately published on the checked page
Max tyre clearance
27.5 x 2.35 in or 700c x 42mm without fenders; 650b x 50mm or 700c x 38mm with fenders
Dropper post
Not compatible

Geometry

All figures in millimetres except angles. Effective top tube and seat tube are the two that decide frame bag fit.

SizeEff. top tubeSeat tubeStandoverHead tubeStackReachChainstayWheelbaseBB dropHead angleSeat angle
40cm500400720955313634259937071°75.5°
46cm5204607511005383664259947071.5°74°
50cm54050077811054437942510076572°73.5°
54cm55554080612556038942510186572.5°73.5°
56cm57056082714058039342510126573°73°
58cm58558084616059940242510276573°73°
60cm60560086618062040942510366573.5°72.5°
64cm62564089520064142342510506574°72.5°

Source — Surly's own geometry chart: https://surlybikes.com/products/midnight-special-650b-black — checked 2026-08-16. A dash means the figure isn't published; we leave it blank rather than estimate.

Note: Current page lists current clearance in frame specs; older snippets may show larger 650b clearance.

Which frame bags fit

Every frame bag we track, checked against this frame's published geometry. Pick your size.

Checking 12 frame bags against a 570mm effective top tube and 560mm seat tube. 12 fit.

Excellent fit
Topeak Midloader Frame Bag

Plenty of room in frame triangle

$65
220g
Excellent fit
Salsa EXP Series Anything Cradle

Plenty of room in frame triangle

$75
200g
Excellent fit
Blackburn Outpost Frame Bag Medium

Plenty of room in frame triangle

$80
280g
Excellent fit
Oveja Negra Super Wedgie Half Frame Bag

Plenty of room in frame triangle

$110
170g
Excellent fit
Rockgeist Half Frame Bag

Plenty of room in frame triangle

$130
170g
Excellent fit
Apidura Racing Frame Pack

Plenty of room in frame triangle

$130
145g
Good fit
Moosetreks Full Frame Bag

Good fit within frame triangle

$60
300g
Good fit
Ortlieb Frame-Pack RC

Good fit within frame triangle

$150
250g
Good fit
Revelate Designs Ranger Frame Bag

Good fit within frame triangle

$155
230g
Good fit
Apidura Expedition Full Frame Pack

Good fit within frame triangle

$175
310g
Good fit
Bedrock Bags Entrada Frame Bag

Good fit within frame triangle

$185
210g
Good fit
Porcelain Rocket Mr. Fusion Frame Bag

Good fit within frame triangle

$195
190g

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.