Speed for Sale

You can’t buy fitness; if anyone offers to sell it to you it’s probably time to call WADA. But as a cyclist you can legally buy performance in other ways: when you are cycling your speed is that at which the propulsion force you generate is equal and opposite to the forces opposing your motion. These forces are many and varied but the main ones we worry about are rolling resistance and aerodynamic drag.

To address aerodynamic drag I wanted to get some toroidal profile rims. These were developed by Zipp and HED over the last three decades and are generally available as either full-CFRP (=Carbon Fibre Reinforced Plastic) rims/pre-builts or as hybrid aluminium/CFRP pre-builts. The full-CFRP option is very expensive and I am reliably informed that the braking performance of plastic rims is still rubbish in the wet compared to aluminium. The hybrid aluminium/CFRP options is basically an aluminium wheel with a plastic aerodynamic faring; they are therefore less-expensive and have good braking performance but are only available as pre-built wheels.

I don’t want pre-built wheels because a lot of the things I think are important in a wheel have been decided in ways I would not have gone for. They often use weird and expensive spokes and bearings. Because people like to compare wheel weights they almost all have aluminium cassette carriers: if you use a cassette with any independent cogs (I do) they dig into the splines of the softer metal on the cassette carrier which causes several problems. I prefer my cassette carrier to be made of steel or titanium so that this does not happen. Another thing I want is the ability to rectify any tension loss which happens over time: you can’t do this on any hybrid wheel without removing the tyre, which makes fixing rear-wheel problems much more difficult (fitting and inflating a tyre affects the alignment of the rear wheel, so I would usually work on alignment with the tyre fully installed). Finally, I just enjoy building my own wheels.

The patents Zipp and HED held on their toroidal shape have now expired, which has allowed a new business named Flo Cycling to start making some interesting products. They started out by making the Flo 60, Flo 90 and Flo disc hybrid wheels which are of similar construction to part of HED’s lineup: the Jet 6 Plus, the Jet 9 Plus, and the Jet Plus Disc respectively. When you convert their prices from dollars and add in shipping costs and import VAT a Flo 60 front and 90 rear has cost a shade under £700 by the time it’s on your bike in the UK. The comparable HED set will cost you £1325 which is a significant difference.

I was much more interested, however, in their latest product the all-aluminium Flo 30 wheel which is also available as a rim only. It has the aerodynamically efficient toroidal shape but is cheap and can be built just like any other aluminium rim. I bought 4 rims, a full set each for Cerys and I, for a total cost just under £260 including shipping and VAT. Two pairs of Ultegra 6800 hubs (my current favourite for usability and value) 128 veloplugs and 112 spokes & nipples & washers bring the cost to around £600 for the whole project. I could have shaved at least £100 from that by using less-nice hubs, but I want these wheels to last 20 years and be nice to ride for all that time.

You may have noticed that I am using 16 fewer spokes than there are holes in the rims/hubs. This is because I am going to build the left-side of the rear wheels with 8 spokes instead of the usual 16. This should result in the per-spoke tension on the left-side of the rear wheel being much closer to that on the right side of the rear wheel: only 4% less rather than 55% less per my calculations. It might look strange (then again it might look cool) but it will be a stronger wheel as a result.

I am also planning not to weave the spokes at their crossing points: each spoke will go straight to the rim from the hub, not deviating to bend around another spoke. This is because I am not convinced that bending the spokes past each other actually does anything useful, and a quick look for broken spoke images on the web shows that they most-often break at the elbow and next-most-often at the crossing point. I do not expect to be able to feel a difference when riding.

As well as aerodynamic drag I also wanted to address rolling resistance. Testing shows that latex inner tubes perform much better than butyl inner tubes, so I have a latex tube per wheel ready to go. The tyre is also important: Flo test with and develop for the Continental GP 4000 S tyre so I will put those on Cerys’s wheels so she has maximum aerodynamic efficiency. I like the feel of my Vittoria Corsa SC tubulars enough to give up some aerodynamic advantage; I am going to equip myself with Veloflex Corsa 23 open tubulars in an attempt to get the tubular-like ride on a clincher rim. We should both have more than acceptable overall performance.

In terms of speed gain over the 10-mile time trial distance we have been getting into recently the new wheels should give each of us a time saving between 45 seconds and 1 minute if we have made no other improvements.

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