Yesterday evening Cerys and I used the new aerodynamic wheels I built in a 10 mile individual time trial for the first time. Now therefore seems a good time to draw some conclusions.
In summary, Flo Cycling have done an excellent job of the aerodynamics with the Flo 30: the bike stability is a massive improvement over anything I have ridden before and to the extent that I can test it their claimed drag reduction seems to be spot on as well. I don’t know of any other rim (or wheel set) that can claim similar performance at anywhere near this price. If only they did a tubular version it would be perfect…
Annoyingly the wind was higher and from a different direction than the last time we rode the course, so it is unfair to directly compare the times. But what else are we supposed to do? I rode a 29.11 (13 seconds faster than previously) and Cerys rode a 39.09 (1 minute and 27 seconds slower than previously). Of the other riders who also rode on both occasions the fastest rider was 1 minute and 40 seconds slower than previously. I consider this a good indicator of the worsened conditions because faster riders tend to be very consistent; although of course we do not know that he used the same equipment on both occasions.
Interestingly this loss matches up quite well with the predictions of bikecalculator.com which indicate that the speed lost to a headwind on an uphill section (as was the case last time) is much less than the speed lost to a headwind on the flat or downhill (as was the case this time). Since slower riders lose more time than fast ones to changes in drag, I think we can reasonably safely assume that Cerys and I would have each lost at least 1 minute 40 seconds had we used the same equipment as previously.
If this is true, I gained a wind-adjusted 1 minute 53 seconds and Cerys gained a wind-adjusted 13 seconds. Why the discrepancy? Partly this is due to Cerys’s more-draggy upright riding position on her trekking bike which is more adversely affected by the wind than my aerobars position, but mostly we think because some saddle-position changes we made to try and improve her riding comfort had the opposite effect. My position was essentially unchanged from the previous trial and is therefore much more comparable, although I did have some shifting issues on the first three laps and had to make a mid-ride adjustment to my aerobar pads on lap 2 which may have cost me some time. I would like to say that these things cost me over 4 seconds because that’s the amount I was beaten by Karun Chandhok (currently driving in the FIA Formula E championship), but that isn’t borne out by the data: the drop in power is quite obvious but it is very short and there is no significant speed change.
Of course it is possible that I have over-estimated the effect of the changing wind and in fact the new wheels have not made very much difference to our speed. However they certainly made a difference to the handling of the bike: I know from extensive experience in those conditions that I would feel buffeting from the wheels if I were riding my box-section rims or the Zonda wheels (which I no longer have). In the past this buffeting has reduced the amount of time I am happy to spend in the aerobars because I’ve felt the need to grab the handlebars for stability. Yesterday I felt no buffeting at all; the bike handled like I was riding in still air.
The braking was as-per-usual for an aluminium rim; the difference between the brake track width of the Flo 30 and my other wheels is about the same as fully-opening or -closing the brake quick releases on my road callipers. You don’t need to open the brakes any further to remove or install the Flo 30 because (at least with a 23mm tyre) the brake track is wider than the tyre.
Currently you are limited to using clincher tyres with the Flo 30 rim. It is supposed to be compatible with tubeless tyres but I cannot see or feel the behind-the-bead ridge which is present on my other tubeless-compatible rims: I have no experience of road tubeless so perhaps this is not meant to be there, or perhaps it is there but I can’t feel it because of the angled-in brake track. Flo Cycling say they have no plans to make a tubular version because there is insufficient demand to justify the R&D cost; perhaps they are right. Still it is a shame that there remains no rim you can buy which gives you good aerodynamics, good ride quality and a reasonable amount of cash left in your wallet.