Super lightweights, deep dishes and crosswinds

I’m looking at upgrading the current wheelset on my 2012 Colnago EPS. I’m looking at Light Bike, and they have a 35mm and 45mm deep rim I can choose from. Here’s the issue: I’m light. I mean really, really LIGHT. I’ve read a lot of threads where guys say “Oh, yeah. I’m light (60-65kg), and I have no issues with a 50/55/60mm rim in crosswinds”. Sorry, but that’s not light. My race weight is ~52-53kg. At peak fitness, I’m at ~215-220 FTP (~4.0-4.1 watts/kg), so I can climb really well. The problem is, I get blown around in crosswinds.

So my question is for you sub-60 kg’ers. What is your experience with aero rims and crosswinds? Should I err on the side of caution and go with 35’s? go out on a limb and do 45s? 45 rear/35 front? I welcome your input.

cheers

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Neither small nor light so I will leave others to chip in on that bit but I am a recovering aerodynamicist and I would just get the caveat in up front that the shape of the rim is going to have a significant bearing on the side load response. So be careful that you are comparing apples to apples there. A round tailed 60 mm is going to perform much better than a sharp tailed 30 mm with a comparable width to depth ratio (here the width refers to the outside max width of the tire/rim combo and not the bead seat width). A bit unrealistic for them to have a comparable ratio but the point is that not all things are equal in rims based on depth.

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My race weight is around 50kg. I use 50mm every day - on flats, winds, in the Alps, whatever.

No problems at all. My thought is - people just seem to notice cross winds using deeper wheels because when they buy deeper wheels they simply focus on that.

Of course strong gust of wind sometimes change my line. Exactly the same as when using shallow rims :slight_smile:

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Excellent point. I’ll try to copy and post the profiles they sent me. What are your thoughts on splitting 45 rear/35 front? Does that have any merit? I wish you well in your recovery :smile:

Cannodale made a big deal out of the rim depth split fore and aft. I haven’t seen much data to back that up, especially for real world riding. So on that and I am agnostic. It may well be true that the drag coefficient is better for a deeper rim aft while the handling merits of a shallower rim up front lead to this compromise. I think there are some interesting assumptions to unpack from that. Most of the air hitting the rear wheel, even from xwinds, is going to be ‘dirty’ to some extent so the actual drag coefficient is likely to be higher than advertised. You want your best drag cutters in the cleanest air to minimize the amount of dirty air being generated. By the time it gets to the rear wheel it is largely game over and you are into diminishing returns. In the realm of marginal gains though disc wheels make sense here for time trialing: The higher forward speed also gives you a lower relative wind angle. However I always thought that the persistence with disc rears on TT bikes was more to do with power transfer.

So I would just go the same fore and aft for a normal bike. Two things to look for in a profile: No Kamm tail (not a fan for real world applications) and no pointed tail. Both enforce the flow separation from a Xwind at the worst point. The very end of the rim. A rounded tail allows the separation to soften around the leeward side of the rim. The pressure differentials are thus lower and the steering upset less abrupt and more manageable.

From my own experience my Fulcrum 3 alloy (20mm deep) rims are worse in an Xwind than my 38mm 9th wave carbons. Pseudo Kamm tail v Round tail.

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Enve does the same thing with their SES wheels and offer the same explanation for doing so.

And they could well be right but narrow use case (Pro bias) could be in play here. Optimizing a product for professional peleton applications (for showcase reasons or just pure ligging) is not the same as our use cases here. Our cycling population rarely spend days on end at 40+kmph and have the bikes buffed daily by a gang of engineers.

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I would gladly buff my own bike daily if I could sustain 40+kmph. Those days are waaaay behind me (53 y/o)

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FWIW if it is your light bike should you not go for the lightest rims? I would guess that is the 35mms. Those should be more or less aero enough. Especially if you are not a watt monster banging out long rides on the flat.

Yes, I consider this my “climbing” bike (other road bike is a 2000 steel frame Colnago Tecnos, that’s my “pure joy” bike). The EPS is a hair over 16 pounds right now, hoping I can nudge it down to high 15’s.

59Kg, I’ve used combinations of 80mm front/rear and disc rear without being blown about on a windy outdoor velodrome, and I bop around the lanes on a set of 50/50’s without any trouble. I notice the wind a tiny bit more on my first ride on the 50’s after a winter on box sections, but never really had an issue or felt myself being blown around. it’s definitely more about the shape of the wheel.

imo if this is your climbing bike, just get a really nice light set of 20mm wheels if you don’t plan on riding fast on them i.e steep climbs.
if you plan on riding them on everything then get a decent shaped 40-45mm. they’ll be light enough to climb on and quick enough on the flats. just make sure to get a good shape.

also lol at thinking 60kg isn’t light, you’re just very petite.

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Just to get it on the record 192cm and 78kg. I hate ye. Ye get all the wind shielding my big carcass offers when I am on the front. I get bugger all when it’s your turn on point. Then ye bugger off up the hills like scalded cats. #whiningoaf

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Luckily W/Kg exists :wink:

Ha tried that route once. I got down to 72kg minuscule improvement in W/kg. I went up the hills marginally better. Shivering I was, all the damn time through the Northern European excuse for summer. Larded back up. Broke some puncheur class PBs.

Re splitting depths front to rear, Josh Poertner has talked about it on Marginal Gains podcast, with respect to TT bikes, but the same should hold true on a road bike. His comment was that the rear wheel has less effect on the wind stability of the bike, so on a TT bike he said to keep the rear disk, and just go smaller depth at the front until stability is achieved. I think if you wanted to be the most aero, a slightly deeper rear wheel, and a smaller front. Full disclosure, I have not tried this, so can’t comment with empirical data.

Well if you can’t reduce the weight… you can always increase the FTP!

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LOL!! I’m 5’7, 117#. My old training buddy was 6’4" and 190. I did the majority of the pulling on our training rides (4-6 hours) b/c I was more experienced. He swore up and down he got ZERO draft off of me. To which I replied, “Then you should have no problem pulling us home for the last hour”. He never did. On the flip side, he would always distance me on descents

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Pfft at 52 with 30 odd years of riding my FTP is going nowhere. Since I got a power meter it has hovered in a 20 watt band. Regardless of what I do.

I blame Coach Chad for everything

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Always a good starting point

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