Spoke Calculator

This spoke length calculator can be used to figure out which lacing pattern to use, and how long the spokes will need to be. It supports many unusual features, such as mixed lacing, offset frames and rims, and high-low hubs. To help decide which lacing pattern to use, it computes spoke pull angles. It also computes spoke tensions for dished wheels and uses this to compute spoke stretch for a little extra accuracy.

Instructions

All measurements are in mm. Use a decent vernier caliper for accuracy. If you're building both front and rear wheels, measure both rims and hubs. As front wheels are always symmetric, you'll enter the same data for both drive and non-drive sides.

  • Enter the wheel data:
  • Measure your rim:
  • Measure your hub:
  • Enter the spoke data:
  • Press the Calculate button:
  • Calculator

    Wish List

  • Make initial values be blank instead of zero.
  • Sort menus either alphabetically or in the order they appear in the main files.
  • Possibly combine all the data into a single file for download efficiency.
  • Use Jdoc format for comments and put resulting html online.
  • Calculate angle spoke enters rim at. Roger Musson suggested keeping this angle no more than 9 degrees from perpendicular.
  • Feedback

    If you find this useful or have any comments, please send me an email. If you send me your measurements, I'll add them to the menus so the next wheel builder won't have to repeat the process. If you find any of the component data inaccurate, please let me know. I suspect there is quite a bit of variation.

    Assumptions

  • The maximum spoke tension (ie. that used on the drive side of a dished wheel) is 180 N.
  • The desired spoke tension (ie. that used on undished wheels) is 3/4 of the maximum: 135 N.
  • Spokes are made of steel: modulus of elasticity = 21000 N/mm2 (from The Bicycle Wheel*). Titanium spokes aren't recommended.
  • The calculator does not compensate for rim shrinkage due to spoke tension. This can reduce the rim diameter by as much as 2 mm, depending on the rim.
  • References

  • * The Bicycle Wheel, by Jobst Brandt. Formulae for approximating spoke stretch were taken from this book.
  • ** Roger Musson's spoke length calculator. Ideas for measuring rims were taken from this web page.
  • This caculator was implemented on Mac OS X using Apple's Project Builder. Here's the source code.
  • This calculator uses JavaTM utilities courtesy of Core Java, by Gary Cornell and Cay S. Horstmann.
  • Sheldon Brown's article on wheelbuilding includes lots of good detailed information while still being readable. It is highly recommended. It includes links to several other spoke length calculators, several of which include large databases of pre-measured components.

  • Version 10. August 3, 2003. Email Danny Epstein