25 : 9
25/9 · classic five-spoke
BMX street 25/9
The straight five-spoke street sprocket, after BSD's Guard.
Sample · BMX street 25/9
25/9 · angled spokes
Five solid spokes set at a 15° Angle Offset, on a 9T driver.
Build it with your AI
Using the CheapCAD Tools connector, design a two-sprocket drive in Sprocket Designer on 081C (⅛" single-speed bicycle) roller chain, 78 chain links. Sprocket 1: 25 teeth, a sprocket; a 23.8 mm bore; spokes: tapered spokes, 5 of them, Hub OD 50 mm, Rim Depth 9 mm, Width at Rim 14 mm, Width at Hub 14 mm, Angle Offset 15°; no tooth chamfer. Sprocket 2: 9 teeth, a sprocket; a 12 mm bore; no tooth chamfer. Check the design, apply any Auto-fix it suggests, then export both sprockets as STL and give me the download link.
Paste it into Claude, ChatGPT or any AI app with the CheapCAD Tools connector, and it designs this drive with you, checks it and hands you the files. How to connect your AI.
What's in this design
Sprocket 1 · 25 teeth
- 25T · ⅛" single speed · sprocket · bore Ø23.8 · tapered spokes × 5, 15° offset
- 205 MPa peak · SF 2.46 in 7075 · rim moves 0.32 mm · 3.07 mm plate · 63 % solid
Sprocket 2 · 9 teeth
- 9T · ⅛" single speed · sprocket · bore Ø12
- 283 MPa peak · SF 1.78 in 7075; make it steel · rim moves 0.16 mm · 3.07 mm plate · 60 % solid
The link opens both sprockets and the chain in the Sprocket Designer's 3D Mode. Change the teeth, bore, hub or spokes, then download STL, STEP, DXF or SVG. Strength figures are the app's plane-stress check of each sprocket in the material it names; SF is the safety factor.
More samples
Related drives
25 : 9
28 : 9
28/9 · six tapered spokes
BMX street 28/9
Six spokes tapering from 16 mm at the hub to 13 mm at the rim, 12° offset.
28 : 9
28/9 · overlapping Y star
BMX street 28/9
Six Y spokes forking into a star lattice, like Wethepeople's Turmoil. On a 25T the forks leave too little room to pass the strength check, so the star is a 28T.