Serk A21M The Dissident

Frameset (from RMB 16,800 / US$ 2599) ships frame + Serk Carbon Adventure fork + Serk semi-integrated headset + seatpost clamp + thru-axles + expander + Ti top cap; "Integrated handlebars are not included." Front end is a choice: "Integrated front end cabling or External" / "Choose Integrated or Non-Integrated version" (internal routing = all electronic groupsets; external routing = 1x/2x mechanical or electronic). Integrated bar/stem upgrade options listed on the page: Deda Super Box / Deda RS2 (+1000 RMB), Serk Carbon integrated (+1200 RMB), THE ONE PRO Carbon Integrated (+1500 RMB), EXS Aerover Carbon Integrated (+2500 RMB, on the Rival build). Complete builds: SRAM Rival D1 AXS 1x = Uno Gravel bar + Uno stem (external routing) + Uno aluminium 27.2 mm seatpost; Campagnolo Ekar = Serk Gravel Carbon bar + Zipp Service Course SL stem (external routing) + Serk Carbon 27.2 mm seatpost; SRAM Force E1 2x AXS = Serk Carbon integrated bar/stem + Serk Carbon 27.2 mm seatpost. NOT published anywhere on the maker site: stem lengths per size, stem angle, bar widths, bar reach/drop, clamp/stack height of the integrated bars, maximum spacer stack, seatpost length or offset. Seatpost: round 27.2 mm (owners manual A21 quick spec), dropper post compatible with internal mechanical dropper cable routing. Headset: ZS44 upper / EC44 lower on the A21 (owners manual HEADSETS section: straight 44 mm head tube, tapered steerer 28.6 to 39.8 mm; compatible with Chris King, Cane Creek, White Industries etc.); the A30M-style EC44/EC44 handlebar-specific headset is NOT stated for the A21. Headset top stack above frame stack: 28.5 mm on the A21M page table ("* Additional top headset stack"); the owners manual A21 table gives 10 mm, and the manual's A40 table labels the same two figures as 28.5 = internal routing headset top and 10.1 = external routing headset top, so read 28.5 as the internal/integrated front end and 10 as the external-routing top cover. Fork: 12x100 mm thru-axle, adjustable rake 47/52 mm via flip chip ("Party mode" 47 mm = more trail, more stable; "Business mode" 52 mm = less trail, more reactive), 3-pack side mounts, internal dynamo wiring, front light mount, 520 g with 300 mm steerer. Frame weights published: S 1750 g, M 1850 g, L 2000 g, XL 2090 g. Frame: titanium 3Al/2.5V, T47 cast one-piece BB shell (68 mm), flat mount 160 mm front and rear (max 160 mm rotor), 12x142 rear, 3 bottle cage mounts, mudguard and rack mounts, UDH not mentioned, system weight limit 115 kg (rider + bike, owners manual).

the headset top cover is excluded and published separately as "* Additional top headset stack" = 28.5 mm every size on the A21M page (10 mm in the owners manual A21 table, see cockpit_options). TOP TUBE: labelled "Top Tube Length" (B), drawn horizontally in the diagram from the head tube top to the seat tube/seatpost line, so recorded as top_tube_effective (assumption). SEAT TUBE LENGTH (A): drawn along the seat tube from the BB; centre-to-top assumed, not stated. SIZES: named S/M/L/XL only; page footnote "*measured size" refers to tyre clearance, not frame sizes. FORK OFFSET: published as "47/52" (flip chip) in one row; recorded as 52 because the wheelbase row is explicitly "Wheelbase (52 OffSET)" and the trail row "Trail (700x42)" = 73.1 mm agrees with a standard trail calculation at 52 mm offset and 700x42 (about 78.5 mm at 47 mm); 47 mm is the alternate position and wheelbase shrinks by roughly 6 mm there (owners manual A21 table: 1009/1032/1054/1075, unlabelled offset, consistent with 47 mm). TRAIL: 73.1 mm all sizes (HTA 70 deg constant). BB DROP: 75 mm S and M, 73 mm L and XL. HEAD TUBE ANGLE 70 deg all sizes. Standover and front centre are NOT published (nulls). No stem length or bar width per size is published (nulls). MODEL YEAR: no year on the page; the diagram file is named geo_2023 (uploaded Oct 2022), the page was published 2025-06-05 and last modified 2026-02-07 (article meta), and the text calls the A21 "our 3rd generation gravel bike"; owners manual A21 table (older copy, external-routing headset stack, mislabelled "Trail (28C)" = 73.7, wheelbase 1009/1032/1054/1075) carries identical frame numbers, so the frame geometry appears unchanged across the A21 / A21M naming; model_year left null. NAMING: the page title is "A21M", the range page (serk.cc/titanium/) calls it "A21 - The Dissident" ("Offroad Anywhere Bike") and the owners manual "A21 | The Dissident" ("Gravel Bike"); the M suffix matches Serk's A30M convention for the internally routed / integrated front end version, and the A21M page offers both integrated and external front ends. Tyre clearance: 700c x 45 / 650b x 55 measured (owners manual says 700c x 40 or 650b x 55 measured, older); geometry "optimized for 700x45mm or 650x47mm tyres". Max chainring 50/34 (2x) or 46 (1x). Source: html_table (maker product page GEOMETRY section: HTML table plus letter-keyed diagram image https://www.serk.cc/wp-content/uploads/2022/10/geo_2023_550.jpg)