S&M ATF 18" Wheel BMX Frame

The S&M ATF 18" is a 100% chromoly, USA-made BMX frame built as a correctly proportioned, scaled-down version of the full-size ATF for younger riders who are riding seriously across park, dirt, and street. The ATF name stands for All Terrain Frame, and the geometry and tubing spec reflect that intent at the 18" wheel size.

Key Features

• Butted Thermal-X tubing throughout — Butted tubing removes material from low-stress mid-sections while retaining wall thickness at weld points and high-stress areas; Thermal-X is a high-quality tubing spec that provides reliable strength and consistent ride characteristics
• Proportionally correct 18" geometry — Top tube, rear end, BB height, and standover are all scaled to the 18" wheel size rather than being a modified adult frame, ensuring correct handling and fit for smaller riders
• 75° head tube angle — Slightly steeper than adult all-around geometry, appropriate for the shorter wheelbase and smaller wheel diameter of an 18" build
• Integrated 45°/45° head tube — Campagnolo-style integrated head tube accepts 41.8mm angular contact bearings directly without pressed-in cups, a cleaner and more reliable interface than cup-and-cone alternatives at this frame size
• 4Q baked 14mm dropouts — Heat-treated dropouts resist deformation and stress cracking under peg use and axle loading; 14mm slot accommodates standard BMX rear axles
• Thread-on 990 brake mounts — Compatible with standard 990 U-brake setups via thread-on mounts sold separately, keeping the frame clean without permanent welded mounts
• Integrated seat clamp — Built-in clamp removes the need for a separate clamp component, keeping the seat tube area clean and reducing parts count
• 100% chromoly construction — Full chromoly throughout provides consistent strength and weight characteristics across the entire frame
• Made in USA — Domestic production with Thermal-X tubing and 4Q baked dropout construction throughout

Technical Specifications

• Brand: S&M Bikes
• Model: ATF 18"
• Top tube length: 18.5"
• Rear end length: 12.4"
• Head tube angle: 75°
• Seat tube angle: 71°
• BB height: 10.5"
• Standover height: 8"
• Head tube: Integrated, 45°/45°, 41.8mm
• Bottom bracket: Mid
• Dropouts: 14mm slot, 4Q baked
• Brake mounts: Thread-on 990 (sold separately)
• Seat clamp: Integrated
• Seat post diameter: 1" (25.4mm)
• Gyro tabs: None
• Tubing: Butted Thermal-X
• Material: 100% chromoly
• Weight: 4.65 lb (2.12 kg)
• Country of manufacture: USA

Compatibility and Ideal Use Cases

Built exclusively for 18" wheel setups — not compatible with 20" or other wheel sizes without significant geometry compromise. Thread-on 990 brake mounts require a separately purchased mount kit. Seat post diameter is 1" (25.4mm) — confirm post size before purchasing a replacement. No gyro tabs are present on this frame — riders requiring gyro compatibility should confirm this limitation before purchasing. Best suited to younger, smaller riders taking their riding seriously across all terrain who need a properly proportioned, high-quality frame rather than a scaled-down afterthought.