Chris_W

In preparation for the Transcontinental Race this summer (4000 km in 15 days between London and Istanbul, self-supported), I want to build a dynamo front wheel with a deep, aero rim, but I haven't found an ideal rim yet.

Reading about aerodynamics has taught me that aerodynamic benefits trump weight savings in pretty much every instance apart from pure hill climbing. The SON delux seems to be the only dynamo hub that is available in 20, 24, and 28 hole drillings, which is what most aero' rims are available in, plus it has very low rolling resistance, so I'll probably use one of those. The spokes will definitely be DT Swiss Aerolite (bladed) and I'd prefer either 24 or 28 spokes to give a solid, reliable, and easy to build wheel, and I'll either lace it radial or 2-cross.

Can anyone give any recommendations for the rim? I've found some all-aluminum options that are about 30 mm deep (DT Swiss 585, Kinlin XR300), which are certainly better than box-section rims, but I'd like something a bit deeper. 40-50mm deep seems to be a good compromise between aero advantage, reasonable weight, and not overly affected by crosswinds (I'm happy riding the Shimano 50mm-deep rims that I have in most wind conditions).

I certainly want a metal brake surface for consistent braking, so full carbon rims are totally out of the question. Alu/carbon rims are a possibility, but these seem very difficult to buy as a rim only, they are normally only seen on complete wheelsets (e.g., the Shimano RS80 C50 that I have). Compatibility with standard nipples, which are located outside the rim are also must-have features (to ease maintenance). Here are the two options I've found so far that satisfy all these criteria:

The Kinlin XR380 rim looks promising: An all-metal, 38-mm deep rim, which officially weighs a reasonable 550 grams.
The H Plus SON SL42 is a 42 mm all-metal rim, but weighs quite a bit more than the Kinlin at 615 grams, which I'm not sure justifies the 4 mm extra height.

Any more ideas?

Unfortunately, there seems to be no independent aero' testing of rims that can bought outside of wheelsets, and I know that using rim depth as a proxy for aero' advantage is a rather simplifying assumption, but it seems that I don't have much else to go on.

BTW, I'll be using a B+M Luxos U dynamo light that I already have (which charges USB devices as well as providing an impressive amount of light). Tires will probably be 25 mm wide to give a bit of comfort on the roads in eastern Europe, but still be efficient. Total weight of Rider + Bike + Gear will be 80-85 kg (180 lbs).

Chris_W

I found one more to add to the list:

Halo Caliber, all metal, 38mm deep, 570 grams.

Another that might be interesting is the rim that is on the Zipp 30 wheel (which is not carbon). It's only 30mm deep, but is not a simple V-shape like most other 30mm alloy rims. I've read that the simple V-shape is good in head-on winds, but is far from ideal at the more common yaw angles of 5-20 degrees. Zipp used to make a model called the 101 but now that they've merged everything with SRAM, they're selling the Zipp 30 instead, which uses the rim that used to be on the SRAM S30 wheels because it has better aerodynamics than the one they used on the Zipp 101. I'm going to contact our local Zipp dealer when I'm at work tomorrow and see if rims are available separately. Hopefully the decals are easy to remove because I wouldn't want to look like one of those posers with Zipp wheels.

Weatherby

HED C2 Ardennes in 25 mm width 24H radial with Sapim CX-Ray. Latex tubes in Vittoria CX_EVO in 25mm width or Continential GP4000 Sii in 25mm width.

Chris_W

The HED Ardennes rim appears to be only 24mm deep and only available as part of a wheelset. Am I missing something, or does this not meet at least two of my criteria (>30mm, available as rim only).

Weatherby

It is available as a rim only.

Your critieria are faulty.

You did ask for ideas, right?

Try the Flo 30.

delcrossv

That would be my suggestion. Check hole count though.

Chris Pringle

Chris,

Is it possible that you might be overthinking this? Given the total extreme elevation this race is likely to have, I wonder if the heavier deep rims should be part of your tactic. If this were overall a flatter/faster course, I could see the advantage of using aero rims. I couldn't find the exact route on the website with elevations et al., but the literature emphasizes on a grueling mountainous route. I personally would be looking into building the lightest wheelset possible (i.e., super light cyclocross rims, DT Swiss/SON hubs and the lightest aero spokes -- all at or under 1,500 grams since the SON hub is heavy) and reducing the overall weight as the main tactic. One could gain aerodynamics advantages mainly from other components and accessories such as helmet, aerobars, skin-tight clothing, an aerodynamic cargo bag for the gear, etc.

I also question the use of 25mm tires through your entire race. It might be wise to consider a new set of fast wider tires (e.g., fast cyclocross tire), say past Croatia. Through those countries (e.g., Montenegro, Albania, Kosovo, Bulgaria, Turkey) with subpar roads, common road constructions, etc., I believe you'll be faster on wider tires at lower pressure. They will also give you more comfort and traction, the latter could be crucial when cornering around loose chip seal or gravel.

But as you already know, the choice of gear, although important, usually takes the back seat compared to a lot of other factors faced on this type of races (i.e., nutrition, managing exhaustion and sleep deprivation, avoiding sickness and injury, carrying the right gear, language barrier, etc.)

ijsbrand

Studying Kristof Allegeart's bike -- he won the first Transcontinental Race -- it seems he went for the traditional 36 spokes and low aluminium rim I would choose as well. Safety first. Old fashioned low rims make for the most comfortable wheel.

Weatherby

50mm deep, 50mph descent, and wind gusts to a tired rider = death.

Weatherby

24 holes in stock. $80.

I am happy with my Flo 30 20H radial front and mostly post in the Clydesdale forum.


https://www.flocycling.com/store/ind...product_id=135

delcrossv

Great rims aren't they. I have a 60 front and a 90 rear on the TT bike. No handling issues even with the 25 mph cross winds of last weekend. Easily tough enough for long distance racing.

You can order a FLO 30 or 60 with 24 or 28 holes unlaced. I don't think radial spoking with a dynohub is a good idea.

Weatherby

They are fast and very modestly priced albeit the rim is a brute. I have bombed down rough roads but only have around 400 miles on them and have not had to touch the spoke wrench once.

The delux hubs permit radial lacing per the website and they come in 20, 24, 28, 32, and 36H. If the OP is fairly light and has a good wheelbuilder, 20H might be the ticket.


SONdelux

Chris_W

Thanks to everyone for your input. The Flo rims look really good. Their 30mm deep rim has been designed with a real aero profile instead of a simple V, so should be significantly more aero than any of the simple V shapes from the other manufacturers. It should also handle fine in windy conditions, so it looks pretty ideal.

I actually already have a 28 hole SONdelux hub, so I contacted Flo and they said that they may have one rim left in that drilling. As mentioned above, SON officially state that radial lacing is no problem on this hub. The other option is to give my 28-hole SON wheel to my wife to upgrade from her Shimano dynamo, and I buy a new 24-hole SON for myself, but that's a significant cost. The wheelbuilder will be me - a professional bike mechanic who has built over 100 wheels in the last 5 years, including tandem wheelsets that we've ridden off-road and some for Clydesdales; all have held up just fine.

As for the comment that I'm over-thinking this and should just go with a simple box-section rim, then obviously your understanding of aerodynamics on bicycles is not that great. The course will contain a few major climbs, and a lot of other rolling terrain, but aero' is still going to be WAY more important than weight (to illustrate this, try using some of the online calculators and vary the input parameters, or look at some of the published data - aero trumps weight in all but the most EXTREME circumstances). Plus, over-thinking and planning is all part of the fun of such an adventure for me. Don't worry, I'm already thinking about aerodynamics for my other equipment (clothing, bag setup, aerobars, but no aero helmet because it may be VERY hot in Turkey).

bmike

maybe have a look at mike hall's round the world record bike?

Photo gallery: Mike Hall breaks round-the-world record | Road Cycling UK



i don't think he ran dyno on the wcr, but he did on his amazing tour divide run.

Bacciagalupe

So doing the math....

Under theoretical conditions, 50-60mm aero wheels save you 25 watts @ 30mph. Let's say this increases your average speed by 0.5 mph. At an average of 15mph, for 15 hours a day, aero wheels means you cover 232 miles instead of 225. At 20mph, that's 307 miles instead of 300.

That theoretical advantage can also be mitigated in various ways, such as a solid day of crosswinds; increased fatigue from a harsher wheel; or time spent fixing a busted spoke. The dynamo hub will also almost certainly incur an aero penalty.

And yes, you do need 50-60mm and lower spoke counts to get a real aero advantage. 40mm with 28 spokes and a dynamo hub just won't reduce a lot of drag.

Ultimately, aero wheels are specialty equipment that are really only good for single-day competitions, with predictable wind conditions, and where the margin of victory is seconds rather than hours (or days).

Fortunately, there are more effective ways to reduce drag, such as a skinsuit (~25 watts), aero helmet (~15 watts), shoe covers (~5 watts) and rider's position. All of these options are cheaper, don't have any weight penalties, and don't cause aero penalties in crosswinds.

So I think you have the right idea. But that for something like the Transcontinental, aero wheels are not the optimal way to reduce drag.

Chris_W

Whether or not I have a dynamo hub is not up for discussion - I want to be able to charge my electronic devices and have limitless, powerful lighting. The SONdelux is the most compact and aero dynamo hub available, and has the lowest resistance, so that is an easy decision. The choice then is purely whether I mount this to a simple box-section rim (Mavic Open Pro or DT Swiss RR415), or if I go with a low-spoke-count aero rim.

The Flo 30 rim appears to be way better than any of the other 30-40 mm V-shaped rims on the market for aerodynamics, and I agree that something deeper than that won't be ideal given the unpredictable weather. The data given by Flo Cycling suggests that the reduction in drag from the rim could be reduced by up to one half by using their Flo 30 rim instead of a traditional rim (see graph below). This may not be a huge amount in terms of overall drag of the whole bike and rider, but I'll take what I can get, and the psychological gain may be more than the actual gain, which is also fine with me.



As for spoke breakages, I used to occasionally have those while touring, but since I've been building my own wheels (i.e., the past 5 years or so, so about 50,000 km across many different wheels), using good quality spokes, I haven't broken one spoke yet on any of those wheels. If our 36-hole tandem front wheel can hold up to some fully-loaded dirt road abuse on a tandem whose total weight was over 200 kg, then I'm happy to trust a 24-hole wheel to carry 80 kgs across Europe. Obviously, I'll have a couple of spare spokes with me just in case.

As I mentioned earlier, I am already trying to optimize aerodynamics in other ways, although comfort still comes before aerodynamics given the nature of the event. I'll either get Castelli's aero jersey, or maybe even their SanRemo suit (basically an aero jersey with integrated shorts). I'm worried about the heat towards the end of the trip, so I'll be taking a well-ventilated helmet instead of an aero helmet. Shoe covers probably won't stand up so well to frequent jaunts off the bike to pee in the bushes and to walk around grocery stores, so I'm giving those a miss (except for some small Assos toe covers stashed away for mild rain protection). I've been using clip-on aerobars for the past 15 years when touring, and wouldn't go without them because they improve aerodynamics AND comfort (I use models that have the elbow pads slammed down on the bars - models that have a significant gap between the regular bars and the elbow pads are barely any better aerodynamically than just using the drops). In group rides, I already spend more than twice as much time as anyone else in the drops, and I'm trying to train those muscles and flexibility so that I can stay there for as long as possible. I'm choosing my bar height based on what is comfortable for consecutive 10-12 hour days on the bike (about 6cm below my saddle height, for a 172cm/5'8" guy).

ronocnikral

Just curious on your thoughts of Charging and using lights with a sondelux on a 700c wheel? I did some research and landed on the new Son28. I badly wanted a Sondelux, but everything I pointed to said the Son28 would be the more reliable solution to lights on AND charging a device at the same time.

Weatherby

The math is not linear. The time benefit is greater for slower riders.

Flo Cycling Blog: FLO Cycling - Cycling Wheel Aerodynamics - How Speed, Time and Power are Affected by Reducing Drag

Bacciagalupe

OK then. Read the "FLO 30 Time Savings at Any Speed" chart.

Under optimal conditions, at an average of 15mph, he'd save about 2 minutes over 40k. If he does 300k in a single day -- which would put him in the top 5, by the way -- he will save a whopping 15 minutes. Alternately, he'd go an extra 12km / 7.5 miles per day in the same amount of time.

If we're talking about a competitive time trial, the differences between aero and non-aero wheels is huge.

In the context of a multi-day, unsupported, variable-wind condition, pick-your-own-route event, where the time gaps between competitors are measured in days, and the 1st place rider averaged 50 more miles a day than the 2nd place rider, I'd say those advantages are negligible.

Using 30mm wheels certainly won't kill him. But overall, I think when it comes to wheels, he will be better off prioritizing comfort and robustness over aerodynamics.

Chris_W

I'm aware that the SONdelux doesn't output as much power as regular dynamo hubs like the SON28classic. However, I can't imagine needing to charge things AND have lights at the same time (I just need to get the Garmin charged up before the evening, and occasionally give the blinkies some daytime juice).

As for the comment about aero rims not being ideal for comfort, then see Mike Burrows' video on "Do wheels affect ride comfort" - he's mounted electrical equipment to bikes and found that there is no measurable difference in bump absorption between shallow and deep rims. Deep rims make more noise when going over bumps, which our brain interprets to mean that they are not as comfortable, but since there is no measurable difference then it's not worth worrying about (yes, I'm aware that this is not the accepted "wisdom" on this topic, but that "wisdom" was not based on scientific testing).

I'm surprised that many people here don't want to worry about aerodynamics. If I was talking about saving half a kg or 1 kg on the bike, then I probably wouldn't need to justify it, but I bet that would have a similar minor impact on my daily speed/distance. Just because weight is easier to measure than drag doesn't make it more important.

Steamer

I think that's because most people don't actually have a clue what drives performance / speed / efficiency, and what doesn't.

Carbonfiberboy 

I'm curious about what tires you intend to run on these aero wheels. I think tires make a big difference to wind resistance, but they also make a difference to rolling resistance and to endurance. You said 25mm, but today 25mm tires come in quite a variety of widths.

To me, aero wheels just feel better. The bike seems easier to drive, especially upwind. Maybe it's all in my head, but I like it. I like aero spokes, too. The top spokes are traveling twice the speed of the bike and there's no worse shape than round for resistance. On our tandem, I'm starting to run Kinlin 279 rims with CxRay spokes. So far, so good. The really good thing about deep rims is that they are much stronger and more apt to stay true. Huge difference. Another good thing is heat dissipation. I'd run deep rims for this application for no other reason than strength. Aero is a bonus. Back when I rode my single, I always randoed on Rolfs. Never had a problem.

Chris_W

I want a pair of tires that are puncture resistant, long-lasting, but roll really well, but obviously aero' is another factor. I've had good experience with Michelin Krylions in the past, which have now been replaced by the Michelin Pro Race 4 Endurance model, which I've just started to use. As most people have reported, their 25 mm version measures about 26-27mm on my wheels.

Flo cycling actually did some aero tests with different tyres mounted on the same rims, and found 23mm Conti' GP 4000S to be significantly better than three other tyres. I've also been happy when running a couple of those tires (in terms of puncture protection and grip in all weathers), so I may run one of those in 23mm on the front for aero benefits, and the Michelin Endurance 25mm on the back for comfort and to have a chance that it will last the full 4000 km without needing to find/carry a replacement.