The 30 mm sweet spot (FLO vs Kinlin)

The takeaway message of this season of UCI races is that as rims go, deeper is no longer better: for years the trend was for ever growing rim depths, to the point that even in hugely mountainous stages of the Giro d’Italia, Rigoberto Uran was spotted riding 60 mm deep rims, in the face of cross winds sweeping treacherous descents. That is no more. As wide replaces deep for the title of aerodynamics Holy Grail, the new vogue is for 30ish mm deep rims in all but the flattest of races. This trend has been picked up at amateur and recreational level, with a number of manufacturers offering round about this size in their range. Crucially, when rims get smaller, carbon fibre is no longer the sole option and hoops extruded in aluminium alloy become reasonably competitive in weight to provide a realistic low cost alternative. In this market, two rims have become the hand builders’ favourite: the Kinlin T 31 and the FLO 30.

Since I left London and stopped working on wheels for the “Richmond Park three laps under an hour” crowds, I have lost touch with what is new on the market, so I was quite excited to be given the opportunity to build a pair of FLO 30 rims BFB (build for beer). These are US imports, which are very competitively priced and are still reasonable even factoring in delivery  to the UK and tax. They are by no means light rims, standing at well in excess of 500 grams each, but FLO’s philosophy is simple: aerodynamics trump weight on any terrain but the steepest of roads, therefore if it takes more material to make a more aerodynamic shape, then so be it. The result is an extremely well finished and uniquely shaped rim, which in some respect resembles the Zipp 101, without the hefty price tag. The rim profile shows a shallow channel and ramps at the sides, suggesting it might be used tubeless, although as it is often the case, this is not very clear and it might be a case of trial and error. The set I built was a 20/24, on Chris King hubs with radial Sapim Laser front and two cross Sapim Race rear. Following religiously on FLO’s blog advice, I used Sapim HM washers for the build. These add a couple of mm to the ERD, which worked out around 580 mm, more or less the same they quote. The slight weight penalty comes in handy during the build, as the rims are extremely round and build a perfect wheel with very little in the way of human input. Some rims are a struggle to build, these are not!

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Front wheel built on FLO 30

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Detail of the front wheel

Despite the washers, I was able to use 12 mm nipples, as the square section clears the rim edge nicely. John is extremely pleased with the wheels and says the reduced drag is noticeable over less engineered rims. I was pleased with the reward too, which far exceeded expectations.

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The BFB economics at work!

I had promised Martin to build him a set of wheels, even if I no longer live in London and that means a four hour round car journey for him (or eight if you forget the hubs at home!) It is touching to have such a loyal customer base, although it means one can never really retire from an activity 🙂

The interest for me was to build a set of Kinlin T 31, which rather confusingly are not tubulars, but conventional clincher rims. In typical far eastern fashion, these come free of stickers or logos of any sort and whether the shallow channel in the middle, in all identical to the FLO’s one, means they are tubeless is again not very clear. The front rim was a 24 holes symmetric, while the rear a 24 holes asymmetric rim. Unlike the FLO, there is no attempt to work with the laminar flow of air around the rim, as the structure is a rather conventional V and the brake track is perfectly vertical. The difference in practice might be less than 5 Watts worth of drag, but if you think how much training you need to do to gain 5 Watts, it might well be worth “going with the flow”. The Kinlin are significantly lighter rims, pleasing the light & stiff crowd more than the full aero one. As rims go, they build reasonably well, although the lighter construction means a 24 holes rim “weaves” between one spoke and the next by a tenth of a millimeter or so, which is easily picked up by  the micrometer gauge fitted on the wheel stand. This is of no concern in practice for the end user, but it’s something I have seen consistently in light rims, most notably in the Shimano CL 24 series. The asymmetric rim does a good job of bringing the left and right side tension closer and with Dura Ace hubs and Sapim Race spokes I got 1250/750 Newtons R/L.

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24 H asymmetric Kinlin T 31

Having time to think about it over a cup of coffee, which one would I go for, the FLO or the Kinlin? My head says Kinlin: lighter, cheaper, easily available and the asymmetric builds a stronger rear wheel, but my heart says FLO: nicer finish, more aerodynamic profile and more upmarket look, even bearing in mind the black brake track will inevitably fade within a few hundred miles.

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4 thoughts on “The 30 mm sweet spot (FLO vs Kinlin)

    • I didn’t.
      To be honest I only used them with the FLO as they advised to do so on their blog. The hassle of having to send back a cracked rim to the USA was the main driver to use washers. Kinlin are available here and cheap, so didn’t bother

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