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Tech articles | Commentary articles | Product Manager series part 3

John Neugent probably knows more about bicycle wheels than anyone else alive. Maybe more about bikes as well. He's spent his life in the bike business, at every level. He now owns Neugent Cycling, a firm devoted to delivering world-class equipment at the lowest possible price. If you are in the market for a set of wheels, please, check out John's site. He really knows his stuff. —Chairman Bill

John Neugent

David L. Stanley's masterful telling of his bout with skin cancer Melanoma: It Started with a Freckle is available in print, Kindle eBook and audiobook versions. To get your copy, just click on the Amazon link on the right.

John Neugent writes:

Einstein once said the most amazing thing in the universe is compound interest. I always liked that quote because it has feeling instead of just raw math. In the early ’70s our shop sold lots of kids’ bikes and tires could be 20” all the way up to 26.” Most adult bikes were 27”, but there was a wide range of sizes. We had pumps and gauges but for the most part, we used our thumb to check tire pressures. Considering all of the different sizes it gave us a good indication of the end result quickly. Every different size had a different volume and therefore required a different pressure.

I always like to cut out as much interim information gathering as possible. When building wheels the key to getting equal spoke tension is radial run out. Plucking spokes and measuring tensions in all spokes is a waste of time. Getting the radial run out under 20 thousandths tells you everything you need to know. I see wheel builders measuring and then recording the spoke tension on each spoke. That may get you there but it’s focusing on the wrong thing. I always wonder what benefit the builder is getting by recording the spoke tensions. You are going to have a 200 pound rider hitting pot holes and jumping curbs that is going to affect the wheel a lot more than initial tension. But I digress.

In order to get a good mental image of tire pressures just think of Boyle’s law. Of course you know what that is but it bears repeating. To put it simply, the absolute pressure exerted by a given mass of air is inversely proportional to the volume it occupies.

I don’t know about you, but for me that explanation doesn’t exactly clear things up so I will state it differently. So in terms of an equation, pressure (P) times volume (V) is a constant (K). Or PV=K. But that doesn’t really help much either so here’s an example that, for me, is pretty each to relate to. 100(P)*50(V) = 5000 so that would mean 50(P)*100(V)=5000.

Boyle's Law

Now that most people are running larger diameter tires and there is much confusion on ideal pressure, this gives you somewhat of a good feel for the target pressure, or you can just use your thumb.

John Neugent was was one of the first to establish quality hand building in Taiwan around the turn of the century. He now owns Neugent Cycling, a firm devoted to delivering world-class equipment at the lowest possible price.