# Wheel Design Charts and Graphs

If anyone's left standing, I've got a couple of quick graphs that help explain two of the more important considerations that go into our wheel specs.

The first is simply the % of spokes you are gaining or losing when you add or subtract spokes. This helps illustrate the point of diminishing returns in spoke counts. The series of points starts at 16 spokes and ends at 40. % change in # of spokes going from 16 through 40 spokesAs you can see, when you go from 20 to 16 spokes, you take away an impressive percent of the spokes in the wheel. Going from 36 to 40? Not so much. The points start to become more clustered at 24 and really get tight at 28. Early on, each spoke you add is a big increment of the number of spokes you had. Later on, each additional spoke becomes less significant.

The next chart is of a concept I call "unsupported span." This is simply the distance between spokes.  Again, as you add spokes early on, you chop that unsupported span down quite quickly. Later on, the gains are smaller. This will have an impact on both radial and lateral stiffness of the wheel. Rim stiffness comes into play a lot here, in a way which I think of as "bridging."  Think of an 8 foot long 2x4 resting on a set of saw horses that are 5 feet apart - there's going to be almost no "sag" deflection in that 2x4. Now think of an 8' long sheet of plywood resting on the same saw horses. Huge sag. Put another saw horse halfway between the two original ones, though, and the sag goes away.

16 thru 40 spokes once again, based on a rim ERD of 588

The law of diminishing returns is evident here again, coincidentally with the inflection coming in that 24 to 28 spoke zone. Must be something to that sucker...

Last is a chart of weight gain, as a percentage of the total wheel weight, from adding the last 4 spokes (so 16 spoke weight gain % is from a 12 spoke wheel). This is based on a 450g rim, a 240g hub, and 5g spoke + nipples.

Again we see a line that is not straight, but there is no pronounced inflection.

The old convention of 36 spoke wheels (the time when 32 spoke wheels were those new-fangled get offa my lawn weight weenie wonders was not that long ago at all) was based on very shallow and very soft rims. Those days are long gone, and today's deeper rims made from harder metals change the dynamic of how wheels work. However, increasing structural imbalances in the move to ever more dished rear wheels work against that. You want to build a strong, durable, stable, stiff wheel, but you balance those features against aerodynamics and weight.

If the tryptophan doesn't get you tomorrow, this might do the trick. Have a nice Thanksgiving.