Choose the chain size.
Choose a 400-series or 500-series chain and the model scale.
299 MODEL WORKS / JOURNAL 052 ARTICLES + 1 TOOL / JUL 2026
GSX-RR / CHAIN / CALCULATION / 3D PRINT
Building a GSX-RR Chainfrom Scratch.
The hard part was not modeling the chain itself, but making it travel correctly around both sprockets and close. So pitch, tooth counts, center distance, even link count, and the lower chain path were calculated together. The rebuild eventually became the basis for 299 Chain Builder.
SCALE1/12
FRONT15T
REAR42T
LINKS122
01 / PROBLEM
Matching dimensions alone does not make the chain close.
CHAIN GEOMETRYCorrect pitch,measured center distance,and stillno guarantee it will close.
PITCH
Changing pitch changes not only total chain length but also the sprocket pitch-circle diameters.
LINK COUNT
The chain must use an even number of links. Even one pair more or less changes the model length substantially.
PATH
Adding sag to the lower run lengthens the path and changes the tangent points and arc geometry at the same time.
02 / CALCULATION
Calculate the required values together.
299 CHAIN BUILDEREnter tooth counts.
Enter the front and rear sprocket tooth counts, or their measured outer diameters on the model.
Measure center distance.
Enter the measured center-to-center distance between the two sprockets on the model.
Choose the path.
Choose a straight lower run or add sag within a specified range.
Send the values to CAD.
Use the link count, pitch-circle diameters, tangent coordinates, and arc radii for drawing the chain.
03 / FINDINGS
What became clear during the model build.
FROM THE BUILDUse 500-series, 15T / 42T as the baseline.
The real chain standard and measurements from the model were combined into one consistent reference for both sprockets and the chain.
122 links can close the loop.
At a 60.5 mm center distance, 61 pairs — 122 links — closed the chain while keeping the even-link requirement.
A final 0.09 mm difference is negligible at model scale.
The calculated closure difference could be checked numerically and judged small enough not to matter on a 1/12 model.
The calculated reference also exposes build mistakes.
With a baseline value available, a mismatch can be separated more quickly into a CAD adjustment problem or a physical build error.
04 / ARTICLES
Follow the articles and the tool.
3 ARTICLES + TOOLDEVELOPMENT01↗MODEL BUILD02↗BEFORE03↗WEB TOOL04↗
299 CHAIN BUILDER RELEASE
Why the tool was made, the input conditions, and the results from rebuilding the GSX-RR chain.
CHAIN & TIRES
The GSX-RR build article covering the finished custom chain together with the wheels and tires.
SWINGARM
Prepare the chain-adjuster area, cover, stand hooks, and the surrounding mounting points before the chain work.
299 CHAIN BUILDER
Calculate the chain geometry and output full-scale SVG, printable references, and copyable values for CAD work.
CONCLUSION
Turn an awkward calculationinto a reusable tool.
WHAT WORKED
Pitch, tooth counts, center distance, even-link count, and the lower chain path were brought into one calculation and used as practical reference values for the GSX-RR rebuild.
WHAT IT BECAME
Instead of ending as a one-off CAD adjustment, the calculation was organized into 299 Chain Builder so the same problem can be solved again.