Determining Spoke Length
 

Hi All

How do you determine the length of a spoke when rebuilding a wheel? I am looking to build up some 700c Wheels using some vintage hubs and rim and not sure what spoke length and nipple size I would need.

Hubs are Suntour Superbe Pro and Rims are Ambrosio Montreal?

Thanks

Arb

A spoke calculator, http://leonard.io/edd/ & http://sheldonbrown.com/rinard/spocalc.htm have found them to give the same result, (other calculators are available) the Leonard site gives details of how to measure your hub & rim, it also has alot of pre-filled data, including for the hub/rim combo you are looking at (with a note to measure to be sure for the rim)

http://www.os2.dhs.org/~john/spoke-length.jpg
Source: Sutherland's 4th Edition

spocalc has a pretty good database of vintage hubs and rims, but if it doesn't have your exact items you can come pretty close by using measurements from similar components, e.g. IIRC, Superbe Pro hubs are pretty close copies of Campagnolo Record hubs, so you'll just need to know whether they're large or small flange and the number of spoke holes. You can find the rim diameter easily with a tape measure.

http://www.mrrabbit.net/wheelsbyflemingapplications.php

Grab the spreadsheet...

=8-)

I once actually built a wheel using that formula to calculate spoke lengths. As I recall, my spokes came out a couple of mm short but I built and used the wheel anyway. I suspect my rim measurement was probably off.

The most common problem folks have with the formula is that they forget that the spokes will end on a circle of the same diameter as they entered for rim diameter. You have to add for the nipple. There are also a few fudge factors of a millimeter here and there, such as the loss of a millimeter or so as the spokes deflect to cross over/under each other, or the difference in spoke hole dimension, vs. spoke length measured to inside of elbow.

This is why I always use the same calculator (which tends to come up short so I add 0.5-1.5mm when rounding). Once you get used to the calculator's bias, you can consistently correct for it and end up exactly where you expect to.