Felled No More: Wheel Lessons in Crosswind Resistance
Firstly, a warning. This post is a product of months of obsession. As such, it is a little technical. And more than a little tedious. And of limited interest to anyone who doesn't live in a part of the world plagued with crazy, un-cyclable wind conditions. Nevertheless, crosswinds really are a big deal for some of us. And as it took me three years to stumble upon a solution, I wanted to share my recent experience.
It began when I started to ride a prototype bike for a project I'm working on with Seven Cycles. Until then I had been content to leave well enough alone. Which is to say, I had come to terms with being unable to ride my (lightweight, modern) roadbike in extremely windy conditions, when the cross-winds would get so bad they would blow me off the roads. I had mentioned this problem to several industry contacts since my move to Ireland; I have even written about it here. Over time I received a lot of advice. And while much of that advice was conflicting, two factors were mentioned again and again as potential culprits: (1) deep rims, and (2) light weight.
Since my own roadbike was not equipped with deep rim wheels (the Mavic Ksyriums I had used from 2012 onward have 22mm rims on the front, 25mm on the rear), I concluded it must be the weight - both of the wheels and the bike itself. It seemed logical enough to accept that a lightweight bike would get blown about the road more than a heavy bike. I would just have to live with not riding it on extremely windy days.
Then the project bike arrived. With its Ti-carbon frame and medley of lightweight components, it was lighter than my Axiom by a good 2lb. When I expressed concerns about this in relation to cross-winds, one of the engineers at Seven suggested that a specific set of wheels - Mavic's R-Sys model - might help. I was cautiously optimistic.
The wheels didn't help. They got rid of the problem entirely.
I could hardly believe it at first and it took me some time to trust the bike on increasingly longer rides in bad weather. But time after time, it really did seem impervious to sideways gusts. Not only compared to my lightweight modern roadbike, but compared to all my bikes, including much heavier ones. So much for the "heavier is better" theory.
There was one time in particular when I was testing the proto bike with its magic wheels, and got caught on a mountain pass just as the weather turned. The wind blew directly from the side at over 20 knots along the exposed road. I prepared for the possibility of having to dismount and walk. But while I felt the wind's force on my body, the bicycle seemed not to care. The front wheel went where I wanted it to. And the bike stayed planted on the road.
It can't be the wheels, I thought at first, and looked for other explanations. The magic-wheel project bike, designed by me, had low-trail geometry. So perhaps it was that rather than the wheels? But fitting the wheels on my Axiom (with mid-trail front end geo) yielded the same results. It was indeed the wheels.
The realisation was frustrating to accept. It felt foolish to have struggled against crosswinds for 3 years not realising that the right set of wheels could instantly fix the problem. But also, Mavic R-Sys wheels are expensive. There had to be an alternative! What I hoped for, was to figure out what it was about these specific wheels that made them so good at resisting crosswinds, then look for those same features in a more moderately priced wheelset.
One thing that immediately struck me as odd, is that the R-Sys and Ksyrium models reacted to cross-winds so differently despite their identical rim depths. The biggest difference I could see, was that the Ksyriums used bladed spokes, whereas the R-Sys used mostly round ones (round on the front wheel, round and bladed on the rear). Were round spokes the answer?
As it happened, we soon had a set of modern performance wheels with round spokes in the house, from the sexy Italian builder Spada. I tested them before they went on one of my husband's bikes. Our impressions were similar: The wheels rode like butter. And they were certainly better at resisting crosswinds than the Ksyriums. But still not as good as the Mavic R-Sys. Despite having round spokes and lower profile rims.
More surprisingly still, the Campagnolo Zonda wheels, which my husband had acquired for another build, beat the Spadas in the cross-wind resistance department, despite having bladed spokes.
This last bit in particular surprised me. Comparing the Campagnolo Zonda and the Mavic Ksyrium wheels side by side, they looked of the same ilk. Their weights, rim depths, spokes, were all very similar. So where was the difference coming from?
I thought about this for some time and could not come up with an answer.
Then one day, as I ran my hand along the Ksyrium rims while cleaning them, I noticed something interesting. The Ksyrium rims have a very sharply squared-off edge to them.
The Zonda rims have an edge that, to the naked eye looks similar, but in fact is ever so slightly rounded. The edge on the Spada wheels was somewhere in between the two. This alone seemed to be making a difference. A bigger difference than rim depth, and than whether the spokes were round or bladed.
I then reviewed the Mavic R-Sys wheels: a dramatically rounded edge. A "u-shaped" edge in current wheel design parlance, I believe. None of my other wheels had such dramatically rounded rims. Could this be the secret to crosswind resistance?
I kid not when I say that I grew a little bit obsessed over this. I even made a chart (and I never make charts! I mean, for godssake!) where I listed all the wheels that we had in the house. I labeled them according to weight (now I appreciate the husband recording these figures!), spoke shape, rim depth and rim shape. Then I gave each a "crosswind resistance score" on a scale from 0 to 10, with 0 being "wind is unnoticeable" and 10 being "bike becomes unridable."
The score corresponded most strongly with rim shape, where the more rounded the rim the more crosswind resistant the wheel. The shape of the spokes and the depth of the rims seemed to play comparatively marginal roles. And the weight of the wheels seemed to matter not at all.
But what to do with this information? After doing some research, I learned that the Mavic R-Sys wheels are actually rather unique in their combination of features in today's market. It seems that nobody really makes lightweight performance wheels with the qualities I am looking for anymore.
So the solution turned out to be old-school. What I have ended up with, is a set of positively scrumptious DIY wheels, built for me by an acquaintance (more on this later). They look "vintagey" but are shockingly lightweight, having been build with carefully selected parts and a low spoke count. They are also remarkably cushy, quick rolling, and fantastic at climbing. With their rounded, low(ish)-profile rims and round spokes, they resist crosswinds on par with the Mavic R-Sys for a fraction of the cost.
Oh, and they're tubular! But that too is a topic for another time. For while my crosswinds problem is solved, my wheel education has only just begun.
Awesome post.
ReplyDeleteYou are the best technical explainer I have ever read.
Have you seen this? Hilarious:
ReplyDeletehttps://www.youtube.com/watch?v=H8qgjyqibwY
I Hope this puts än End to the fashion among commuters to use deep "aero" rims. I think it's inherited from bike Messengers and velodrom cycling.
ReplyDeleteI agree that aero rims are unnecessary for commuting, unless one's commute doubles as TT practice. But in fairness, for the vast majority of cyclists they shouldn't really have any adverse effects either (except maybe that some of them make the ride harsher), as the wind conditions I'm talking about here are not typical for most places.
DeleteFor the last few years I've lived in a town in a particularly windy part of the country. My commute takes me through the town and out into the plains for about fifteen miles. The wind can be constant or in gusts or both. It's interesting how it can funnel through the streets and hit from all sorts of angles, literally blowing me off the road sideways. Anyway, because of the length of the commute I need an efficient and lightweight bike though it's equipped with panniers and fenders…all this makes me like a giant wind sail. Are you saying different wheels will make the ride easier?
DeleteYes. In my case the difference was dramatic (between not being able to ride at all under certain conditions, and not noticing the effects). Look for a lightweight set of wheels with low profile rims, a rounded rim profile, and round spokes. You will not find many off the shelf options that combine all of those features. But your nearest wheelbuilder should be able to make you a set for a reasonable price.
DeleteI see them all the time around where I work (there's an evening road cycling group that uses the main drag). At least one of them even has straight soild-disc velodrome rims.
DeleteA bike that was 2 lb heavier than another would only affect the total weight of bike and rider by less than 1.5%. No wonder weight wasn't a factor.
ReplyDeleteI would have assumed that some of your heavier, more utilitarian bikes would have had non-aero rims with rounded edges and round spokes, so they should be even better. Or is a box section rim not rounded enough, so a semi aero is best?
ReplyDeleteIt would be great to have seen some cross section comparison. I guess Mavic doesn't give nice line art cross sections of its prebuilt rims, but the cutaway view of the R-Sys SLR on their site does show things well.
It seems to be not so much about aero/ non-aero, as it is about that rounded edge. I had never paid attention to this before, but yeah - all of my vintage/ utility bikes have pretty square box section rims.
DeleteThere is a good cross section comparison I've come across; let me find it and I'll link it up.
If you're going to pick between rims that are very poorly shaped for crosswinds, a box-section could beat a deeper-section rim simply thanks to being a smaller profile. But more suitable aerodynamic shaping can easily be more significant than a slightly smaller profile. (Similarly, modern bicycle tubing is often much wider than vintage steel tubing, but a carbon aero frame measures less resistance in the wind tunnel.)
DeleteMarkH - Ah, I was thinking of this. But upon revisiting, I see it actually shows only a limited selection.
DeleteHTupolev - Would you class the Mavic Ksyriums as box-section rims? For me, they are unridable in crosswinds despite the low profile. Whether a deep section rim would be "even more unridable" I do not know. Although according to this, not necessarily.
> Would you class the Mavic Ksyriums as box-section rims?
DeleteWith "box section" I'm mostly thinking of the ultra-shallow classic rims which basically cut off below the brake track. But I guess the Ksyriums are a bit like an unusually deep box-section rim, which might explain why they're so poor for cross-winds.
Would you say that something like the Velocity Quill (http://www.velocityusa.com/product/rims#models-tab) is a good shape? What about the Cliffhanger?
DeleteWhat would be the optimal radius of curvature? Is it that bad to have a sharp transition from the braking surface to the top, aero/U-shaped section?
Other rims (as found on the prowheelbuilder.com website since it has a lot of cross sections)
DT R460, Enve Smars SES 2.2, HED Belgium C2, or Pacenti SL23?
Can you tell that I'm planning on building up a wheel soon? :)
wow! genius
ReplyDeleteI suppose after a certain depth it would start to matter more, as you start to get more like track rims after a bit. I vaguely seem to remember bladed spokes being to reduce turbulence within its own plane. But, it has been a long time since I've really thought on bikes.
ReplyDeleteAlso, somehow missed that you'd gotten married somewhere along the way!
Flat spokes and squarish box section rims would create significant drag in a crosswind. Airflow does not like abrupt changes in direction and eddies form when this occurs. These eddies are drag and as such push the bike rather than letting the air pass through. A mid size section rim, say 28mm that has a U shape at spokes side coupled with round thin spokes would be best in crosswinds I believe.
ReplyDeleteThis is good stuff, detective! My light, fast road bikes with their custom wheels perform swell except in crosswinds when they get pretty scary, suggesting I'm about to go airborne. I am flyweight so have just got in the habit of driving my vintage Miss Mercian on very windy days as it just does better. Your post is really intriguing news. Thanks! So impressed you figured out a DIY solution. Also, am building a vintage Italian racing bike up and would love any recommendation for a tubular tire for general all around use (not racing) that you might care to share. Jim Duncan
ReplyDeleteIt is a delight to follow your growing interest in an command of bicycle technology. I venture to say that you probably have expert help in the neighbourhood. Every gliding club counts at least a couple of aeronautical engineers among its members. Give them a few pointers to the literature on bicycle aerodynamics and soon they will be able to answer all of your questions in great depth.
ReplyDeleteI should stop now. But let's carry on, with the sole purpose of dispelling your fear of appearing too geekish before your readership, by providing a much more robust example of the type.
You wondered whether spokes or rims governed crosswind stability and found the answer empirically. A simple theoretical approach this question would be to calculate the side area that each element presents to the crosswind. Even a shallow rim has about three times more area than twenty or so bladed spokes. Furthermore, one must take into account how far each bit of the wheel is to the steering axis, as the further away, the greater the effect of any lateral force upon the steering. This calculation of the 'moment of inertia' is a bit involved but the end result is that the influence of a shallow rim such as a Ksyrium is more than an order of magnitude greater than that of the spokes.
You then pondered the shape of the rim and hypothesised that sharp edges entail sharp manners while rounded edges lead to smoother behaviour. This is not true in all cases (aerodynamics is devilishly tricky) but in general, yes. Technically, airflow tends to detach from surfaces that are not streamlined. The transition to detached airflow is also called stalling.
How exactly does this affect the steering? Consider a boxy rim. The airflow over the whole trailing half of a box-rimmed wheel is permanently stalled because it presents a non-streamlined face to the wind. The front half of the wheel, however, presents the rounded profile of the tire to the airflow. The flow there will be at times attached and, when lateral gusts increase the angle of attack beyond a critical angle, will detach suddenly. It is thus the front half of the wheel that causes most of the steering instability with shallow box rims.
By contrast, when a rim has a rounded U-profile that mirrors the profile of the tire two good things obtain. Firstly, the airflow over the whole wheel tends to attach and detach simultaneously. Therefore, although the lateral forces on the wheel may be as large and unpredictable as the gusts that cause them, the effect on the steering will be more or less neutralized as the lateral forces before and after the steering axis cancel each other. The second effect is harder to explain succinctly and I will not try to do so here (but you can ask you club engineer to explain the delightful Fauvel tail-less gliders and their self-stable wings). It has to do with the pitching moment characteristics of the rim cross section. A longitudinally symmetrical cross section generates a weak pitching moment. This is one reason why modern deep U-shaped rims are much better behaved than the V-shaped deep rims of yesteryear.
Truthfully it is difficult for me to generate and sustain an interest in the technology aspect of things. Generally something has to feel seriously wrong for me to go there. Otherwise I am quite content to ride a bike with whatever components happen to be on it. I mean it took me 7 (!) years to start caring about wheels!..
Delete"I venture to say that you probably have expert help in the neighbourhood. Every gliding club counts at least a couple of aeronautical engineers among its members. Give them a few pointers to the literature on bicycle aerodynamics and soon they will be able to answer all of your questions in great depth."
I did exactly this with the person who happens to live very close by indeed. It took a while to get my husband interested. And actually he did not find it immediately intuitive to apply his extensive knowledge of aerodynamics in the context of aviation to bicycles. But with this wheel thing, I went on and on about it so much he finally got into it, not only "confirming" that my findings made sense according to his understanding of things, but getting excited about other bicycle aerodynamics questions in a way that is, frankly, a little frightening (the word "fairings" gets uttered). So ...yeah!...
Fairings, that's a rabbit hole he might never crawl back out of. Lot's of benefit to be had with perhaps even more hassle.
DeleteBetter to just content himself with the dopey tricks the modern Bicycle Factory calls aerodynamic innovation and avoid the possibility of ending up riding around the neighborhood in a suit of Mylar Armour fashioned after a Codfish.
Fairings, heheheh...
Spindizzy
Have always considered you a sorta princess and the pea kind of character, I am, too. Being sensitive to the smallest of variations, and while my field is different from yours I also ride bikes and can sense your curiosity and obsessiveness wit regard to exploring the possibilities. It's interesting, those things that make one alert and onto the next day.
ReplyDeleteCertainly I am when it comes to some things. But this particular issue is not a subtle one. Again I am not talking about normal wind conditions. In New England I rode on (what I thought were) windy days and never really cared what direction it was coming from. But now I live in a place where winds of 20mph+ are a usual occurrence. Many cyclists just don't go out on their bike in those conditions, feeling unsafe. Like me, I am sure they would be delighted to discover what a huge difference a different set of wheels can make.
DeleteEven my husband, who is not exactly the princess-and-the-pea type, went from "Crosswinds? Yeah, gotta live with them" to "Holy f*** wheels make a huge difference!"
'But now I live in a place where winds of 20mph+ are a usual occurrence. Many cyclists just don't go out on their bike in those conditions, feeling unsafe.'
DeleteBelieve me, I'm not a recreational cyclist and live in an equally windswept environment, besides the constant 20mph+ we've got gusts which may go up to 40mph, and my bike is my only means of transportation. It's tricky riding, especially when a fast moving truck zooms by and alters the wind dynamic I'd been bracing against. My wheel set are Super Champions from the 80's with standard round spokes, I doubt I could improve on them. Yes, wheels make a difference on many levels. You've been consistent in defending and justifying every purchase and change in you bike oeuvre as your experience and interest grows. It's normal. Thanks again, for your thoughtful sermon.
"besides the constant 20mph+ we've got gusts which may go up to 40mph"
DeleteYup, seems like we ride in very similar conditions.
The trucks zooming past are a whole other matter here. Most local cyclist deaths here (which, in fairness, are few) have been of riders doing TT practice on the local highway and getting sucked under by such beasts. I had not even realised such a thing was possible, until I experienced a (thankfully, mild) wind-suck effect from a passing lorry myself. I try to stay away from any road where large trucks travel at high speeds.
"lightweight...remarkably cushy, quick rolling, and fantastic..."
ReplyDeleteI would have thought that was how any good bicycle wheel would be described. My wheels are all like that and have been for a half century. Both the wheels I build myself and the ones that come with bikes I find. The nicest front wheel I have in current use was built sixty years ago and is used just as found. All who ride deserve wheels that good. It should not be anything unusual to have wheels like that. There is not a technical reason why all wheels could not be as good.
I've been building them about as long as I've been riding them and I still can't completely predict how they will ride. That a sharp edge in place of a curve would make so much difference comes as news to me. And I think it's a valid conclusion. The gentleman who supplied the Araya rim in the final photo, and supplied the 1940s Raleigh washers inside the rims, also happens to be the first person ever to put a bicycle in a wind tunnel. A research tool he is not so enamoured with any longer, as it is difficult and unlikely to create a protocol not freighted with assumptions. "Try it and see" is just as good a method. Maybe better, as experiments can be repeated on every ride.
This has been a much more interesting trip than expected. Thank you.
Should have added "compared to other wheels I have ridden."
DeleteI think the very obvious problem is that I've been riding almost exclusively wheels that are, for a rider of my weight/power, overbuilt. This goes both for the 32/36 spoke classic wheels, and for the modern Ksyriums. But as I am sure you know, it is not easy to find alternatives off the shelf. The Mavic R-Sys wheel is not popular. Bigger riders complain of flexibility, broken spokes. For the same reason many bike shops are reluctant to build a classic wheel with fewer than 32 spokes; maybe their experience tells them that a *typical* customer (who is maybe 5'11" and 190lb) will complain of flex, break spokes, try to return it. Problem is I am not that typical customer. Aside from their crosswind resistance qualities, the Mavic R-Sys and the DIY wheels pictured here are the most comfortable wheels I've ever ridden. The difference is a huge one, not a subtle one. I don't think I can ever go back to not caring about wheels.
Your DIY front is suitable for a rider of 100 kg. I'd rate it even higher were it possible to build with carbon steel spokes rather than stainless. Rear rims for 11 speed wheels are a problem.
DeleteFew LBS will build wheels any longer. Many young mechanics have never done the job. The process is billed as arcane and treacherous. Owning a spoke threader is expensive, maintaining spoke inventory in every length is expensive and time consuming. Liability is always a consideration. Selling pre-built wheels is easy and profitable. Anyone so motivated and adventurous as yourself would not be sold a set of wheels priced like Aksum or Zonda.
A couple months back I was on the MUP during morning rush and flatted. Within moments an earnest bearded young man pulled over to assist me. He identified himself as a shop mechanic and instantly brandished an assortment of serious looking tire jacks. I showed him that I could lift tire from bead with two fingers and then let him try. He'd not seen anything like this before. Once a rider or wrench has been trained that it must always be difficult then they will accept any level of nonsense and pay silly high prices to enjoy even a bit of ease. My perspective is different. If any bicycle related task is really difficult I see that as unacceptable. When I encounter a tire that needs special tools, barked knuckles, and the possibility of poking out my eye, I remove it by cutting it off. It's not worth anything anyway.
You're spoiled now. You're going to have good wheels and hopefully more good stuff. For the time being it is still possible to have handbuilt wheels.
With tyres I find that I can either remove them using my bare hands, or not at all. I have never found levers especially helpful and don't usually carry them in my tool kit. Funny thing is, I get a lot of criticism for that should anyone notice their absence... which, ironically, only happens when said criticiser needs to borrow my multi-tool.
Delete"wow you carry a multi-tool but no tyre levers?!!"
"yeah, because sometimes the tools come in handy, but never the levers."
"that's crazy."
"um, you are borrowing my tools right now! I'm not borrowing your levers, am I?"
Cyclists also like to tease me for carrying a mini-pump instead of a cartridge, only to later sheepishly borrow my pump.
Point is, we all develop ways of doing/ carrying stuff based on our experiences and abilities. Ride and let ride.
The issue of what tools to carry is full of interesting possibilities. Do you carry for what's most likely to happen or what would be most disabling? If on a group ride, carry only the tools you (think you might) need or those which others might need too? To an extent it overlaps with the idea of self-sufficiency, also with maintenance and decisions of speed vs security; and a whole lot more! Some carry nothing at all, but there is also a corroborated example of one rider welding his frame together mid-audax. No, he wasn't actually carrying a welder, he got it done at a garage, and it involved a whole string of lucky coincidences such as this (car) garage happening to have, somehow, a crank-removing tool!
DeleteReally intriguing insight about the rim shape affecting handling in crosswinds. I always found those old Kysriums heavily affected by wind--even more than Cosmic Carbone 50mm deep dish rims. Newer Kysriums with rounded rims aren't so affected by wind, especially the Pro SLs. I had wondered why but didn't consider rim shape.
ReplyDeleteOh, that's interesting. What year did they start doing that? My husband's late-2015 Honey came with Ksyriums that are identical to my older ones.
DeleteI think Mavic Ksyrium wheels are in many ways an ideal choice, especially for heavier riders and those who ride on bad roads. So if they eliminated the crosswinds problem that is good news.
When Mavic changed the Kysrium rim shape.....
ReplyDeleteIt may have been 2016. The current Kysrium Pro rims are, I think, the same as the R-Sys rims you tested. I agree with you that they're great wheels for heavier riders and lots less expensive than the R-Sys. The Kysrium Pro Exaliths are available from some online retailers in Germany for less than US$ 1,000.
This is a very interesting post. I also have a very practical interest in bikes and wind, since here in high desert New Mexico we get a great deal of wind (average of almost 12 days/year with gusts to 40 mph, says one reading of the Nat Weather Service) and 20 mph is routine.
ReplyDeleteBut I've only once been blown sideways off my track (while crossing the Rio Grande with panniers on an exceptionally windy day; good thing for concrete barriers!), and the only regular trouble I've had was on bikes equipped with large front mounted bags (ironically, one of these was an old, low trail Herse).
So, reading your post and discovering that "semi-aero" shapes work best in crosswinds made me realize that my 20-year rim favorites, the 559 bsd Sun M14A (my road bikes have 26" wheels, and, the Suns, while narrow, are exceptionally light at ~370 grams and superlatively strong) are, by pure serendipity, also the best for crosswinds -- no wonder I've been relatively untroubled by our winds. I always thought that the "semi-aero" profile was semi-useless marketing, but apparently, at least ex post facto, it works for something.
"wheels with low profile rims, a rounded rim profile, and round spokes" - those may be hard to find if you need them for your road bike, but if you switched to wide tires and disc brakes, you wouldn't have this problem. Plenty of options of disc-specific rims that have rounded low-profile.
ReplyDeleteOoh I think I may need a valium before responding to that : ) But yeah...
DeleteYup. Recently acquired a Cervelo R3 disc which comes with HED Ardennes Plus GP wheels. Got to test out how crosswind friendly they were during http://www.abc.net.au/news/2016-10-10/victoria-strong-winds-thousands-still-without-power/7917278
DeleteSo much nicer than my previous windy challenges :-). The disc doesn't seem to hurt either, I guess it's so close to the centre of the wheel, any wind that doesn't go through the cooling holes pushes evenly and predictably.
This is such an interesting topic. Your scientific approach is reminiscent of some of Jan Heine's research in Bicycle Quarterly. My wife had an unpleasant crosswind experience a few months ago. She was on a training ride on her triathlon bike and was overtaken by a fast-moving storm front. She said she was scared to death about being blown over and even unclipped one pedal as she descended a hill. I suggested that the twitchy handling of her tri-bike may have contributed to her discomfort, but I never thought that the bladed spokes might also be a factor. Thanks.
ReplyDeleteNot to be pedantic (she said, before proceeding to be pedantic), but this is at best a quasi-scientific approach. Or more realistically, a smattering of anecdotal evidence. It is enough to suggest that a scientific study ought to be done though, in a controlled and systematic manner involving testing wheels that differ in only one feature at a time, and multiple testers. It would be great if an institution with the resources to carry out such a trial, would.
DeleteOK, maybe I should have written "scientific" in quotes. But it was close enough for me, the non-scientist.
DeleteA Tri bike, or any other bike that stretches you WAYYY out over the front wheel(Specially' if your saddle is far forward like is the fashion on TT and Tri Bikes these days)is going to be unpleasant descending in the best of times. Going downhill with the bike a-trailing behind your behind in a crosswind is just a good way of illustrating why that sort of set-up is ideal only for the Laboratory Experiment that is Triathlon.
DeleteSpindizzy
Really nice work, both the product-research part and the do-it-yourself-cheap part. It's like Bicycling Magazine circa 1980 or, as the commenter above says, Bicycle Quarterly now. Rare stuff these days.
ReplyDeleteWalter
Very interesting. I also HATE crosswinds – they are even worse than headwinds! – and as I'm about to have a front wheel built (with dynamo hub) I'll ask the builder about using a rounded profile rim. I agree too that most wheels are in fact overbuilt, though I guess this is better than underbuilt!
ReplyDeleteI'm glad that after months of obsession you've found your solution -- your peace. May we all be as fortunate as you. Cycle on, into the wind, across the wind and, if you're especially blessed, with the wind at your back. I will share your discoveries and insights with my wheel builder.
ReplyDeleteWell, that was interesting! And useful (I live in Scotland, another country where it's sometimes a bit breezy). I bet you are right. It seems like a rare profile now. Did you try any rims with a section like this:
ReplyDelete_
/ \
| |
if that makes sense? (They seem to be more common than the shallow curved "U" you found to be the best, perhaps even more so now than a classic right-angled box section rim finishing immediately past the braking surface, like an old Mavic MA2 or whatever).
Couple of things:
(1) Hate to be a misery, but I bet that the old tubular rims that worked in the end won't last. They don't seem to have eyelets from the photos, and are hard anodised. I think they will fail by cracking at the spoke holes long before the brakes wear through the rims. Five quid says it starts on the rear wheel with each cassette-side hole cracking, with an each way bet on you eventually seeing it on the front too (what is that - a 28?)
(2) Surely it's your tyres that determine whether the wheel is comfy or not? Any wheel built so loose that it provides a noticeable degree of comfort is not going to work.
(3) Still reckon nearly everyone would benefit from proper wheels rather than the factory-built ones. Those Ksyriums for example, have a deep-but-not-aero profile, take weird spokes that are very expensive if indeed you can find them, the other bits aren't realistically replaceable either, aren't even especially light. Apart from being profitable for Mavic, I can't what the benefit is.
s.
Eyelets?! Eyelets add weight, innit.
Delete24 spoke. I will let you know if they fail.
I don't have the Mavic MA2 rims specifically, but I do have some with a similar looking profile (sometimes it is difficult to tell going by pictures alone though). What seems to matter is not the curve of the U but the edge, if that makes sense. Some rims are U-shaped in the middle, but have a sharp edge. Others are more square, but have a rounded edge. The latter resists crosswinds better.
24? Damn, should have gone to win instead of each way...I have a 20-spoke wheel in the loft almost identical to that. And yes, it has the cracks. It will probably end up looking like this:
Deletehttp://www.sentient-entity.toucansurf.com/travelshots/technical/anodising_example.jpg
Curved edges then. Will keep an eye out...
Thanks again,
s.
Steve
ReplyDeleteWith regard to your points 1). I built and used that very same rim in 20 hole. Back then I weighed around 80 to 85kg. Used up two front rims like that, the first died when the brake track wore through. The second went 10,000 miles or so before I gave it to a junior racer. He won his next three races. That rim later died in a crash. As for cracking, there are washers inside Velourias rims. Excellent 70 year old washers from Nottingham. I just wouldn't build a non-ferruled rim without washers. As for the drive side rear, I fundamentally disapprove of 11speed wheels. The rear rim in the set is current production, as an Araya ADX would be hopeless for a modern rear. All I can say is that wheel should be better than most.
2) The front wheel was pulled to 80 or 90 kgpf. A lot of vintage wheels are so loose you can't even get a reading. They work anyway, although I wouldn't want to take them down a mountain at speed. The former prevalence of very loose spokes is the
reason we have 36 spoke wheels. You are correct that most of the comfort is coming from the tires. Still, the wheel is old school enough to be missing the sharp edge of modern cartwheels.
3) I will just agree with you about the total weirdness of Ksyrium wheels. Astonishing that no one even notices that big fat square hump in the rim at each spoke. A big square sharp cornered hump 18 times around a rim is not good aerodynamically. That giant sharp edged spoke nipple is pretty horrible aerodynamically as well. And you can slice your fingers on them. Mavic makes those rim humps by extruding a very thick rim and then doing an extraordinary amount of machining. Given that Mavic is notorious for their erratic extrusions the extra machining does not inspire confidence. All that work to accomplish the same thing I do with a washer. The new rims machine the hump until smooth and rather smaller, it is still a crazy amount of monkey motion to substitute for a washer. The only Mavic rims I want are SSC or the old ones with the diamond shaped decal and the brevetatto Longhi stamp.
My impression is, that the main draw of Ksyriums is their durability / to weight / to cost ratio. Big guys who would break other wheels in the same weight category can ride Ksyriums. They can even ride them over potholes. Remember also that while we think of them as modern, these wheels have been around for a while now. Guys around here ride "vintage" Ksyriums, and they can't break them even if they need an excuse to get new wheels.
DeleteYes, the wheels look ungainly, are no doubt made awkwardly as you describe, and the spokes are weird. Yes, if you break some, depending on where you live repair could take a while and involve special ordering. However the Ksyrium owners I know would argue that to be a moot point, considering how seldom this has actually happens to them (i.e. never).
Personally I no longer use Ksyriums, and do not plan to go back to them. But for a lot of riders who want strong modern wheels off the shelf (or secondhand), they make sense, especially considering the cost.
About everyone I know who has had Ksyrium has had problems. I do not work in a bike shop, have seen at least a dozen with rims cracked wide open. In earlier years I had two wheels myself, one given to me by a disgruntled owner, the other garbage picked. Each needed a new spoke. Since the spoke/nipple/wrench configuration has changed a dozen times it was completely impossible to get a spoke. Mavic did not think older wheels should be repaired and I will now agree with that. Sometimes something as simple as giving one spoke one-eighth of a turn to bring the wheel back to true just cannot be accomplished. And you wouldn't want to look inside the hubs.
DeleteKatrina with Al spokes are great, with two significant caveats (or three if you count the freehub bushing wear as a problem): 1. they are round, true, durable until the spokes start fatiguing, as they will under heavier, high mileage riders.2. they are not especially aerodynamically efficient, and they are the scariest 30mm deep wheels I have ridden when presented with gusty crosswinds.
DeleteThe Wolber Profil rims work much better. In 24 spokes, and reasonable spoke tension, they did not crack for lighter riders. They do wear the brake pads oddly....
Best,
Will
William M deRosset
Well, now I need to find a well-profiled 32h rim to lace up to some waiting hubs. We get some damn windy weather here and lots of big trucks, and I would greatly appreciate any crosswind cutting edge... Would love to see a shortlist of rims you've spied that fall in line with the profile you've described!
ReplyDeleteI haven't spied that many, but will try to put something together. Email me, or check this comment again in a few days.
DeleteThere are a lot more rims that pass the test than fail the test. There are a handful of rims that sort of fall in between, for example a Velocity A23 kinda sorta has edges and the machined sidewall version is edgier than the regular. For that handful of rims it's a judgment call and a more testing required situation. Look around the web, profile drawings of any rim you are considering are not hard to find. Or look at what your friend are riding.
DeleteIf your daily riding routinely places you in potentially dangerous situations you want more steering stability. Move the saddle back, shorten the stem. Reduce your own aero profile with snug fitting clothes rather than sails.
I've just found that DT Swiss RR411 and R460 have a "rounded" profile (a pity they are not in silver). They might result in a nice clincher with some level of "cross wind" resistance. According to your tacit knowledge (feeling), what do you think about their shape?
ReplyDeleteVelocity Quill has a nice rounded blunt shape with no edges visible or felt, even with machined sidewalls. Comes in polished silver and flat black.
ReplyDeleteWouldn't the pronounced V edge in the center (or off-center) of the Velocity A23 indicate it would catch wind the way Velouria has found? From her experience reported here I'm not assuming the only edge that counts is an edge near a brake track. A prominent centered edge seems likely to catch wind too.
One consideration that's not necessarily included in Velouria's excellent informal testing was the way the tire profile interacts with the rim profile. The wheels she compared all had a tire about the same width as the rim or only a little wider. I wonder how a rim profile responds with a wider taller tire like a Hetre or Compass BabyShoePass? Does the greater surface area of the bigger tire make rim shape less important since it's a smaller proportion of the wheel profile, or do rim edges catch wind regardless of tire size? I'm inclined to think the tire/rim act more as a single shape in a cross wind.
--Mitch
As I read this, the rather unique service you offer the cycling world became apparent. You are reverse engineering the bicycle from an empirical rather than scientific or engineering methodology. This is rare and very helpful.
ReplyDeleteA while back* you suggested to Bella Ciao it might be interesting to change the trail of the front fork. In writing on this, you presented an understanding of how trail affects ride... not in theory, but in reporting real-life experience with a real bike. Sure, others write on such subjects, but not in a manner that is easily comprehensible by the amateur rider.
You wrote similar articles on different tyres noting how Schwalbe Delta Cruisers were a good all-around solution for the city rider. Now, again empirically you call attention to how wheel profile affects performance in strong crosswinds.
There probably was a time when such subjects were common knowledge among bike makers and town & country riders... I think for example of the tensile steel properties that appear to have been lost when Raleigh wound down its Nottingham factory and the men who made the bikes gradually made their way toward retirement homes and the grave.
Today, the great frustration comes because bicycle manufacturers seem to be chasing the trends rather than mastering the engineering. There are pockets of knowledge left, especially in Europe, but few who bring these engineering elements to a wider readership.
I have a suggestion. Perhaps you might consider consolidating these empirical findings in a section of your blog, and upgrade the articles with examples, such as the cross section of the kind of wheel you find works in wind, and a list of the wheels you find that tend to work. It might be nothing more than adding links under your current Geometry and Fit heading (which has no links yet), although you might want to rename it.
*http://lovelybike.blogspot.co.nz/2015/07/choose-your-fork-adventure.html
Thank you, C. I do need a better method of organising this site.
DeleteAnd I am cheered to know there is a lovelybike.blogspot.co.nz : )
Nevermind the wheels. Am I the only one who gets and enjoys V's musical references?!
ReplyDeleteYes, I'm afraid so : (((
DeleteV, I've alway (since your first blog year) loved that you give the feeling of the experien e then quatify it. That is reality. A parallel is the music of Bjork.
ReplyDeleteAnyways, having Open Pros on my bikes when I lived in TX and OK made me learn about riding in big wind. As a sailor, I knew about apparent wind angles, which is where bike wheels spend a lot of time.
Wish I had the link, but eventually I read about rim design in regard to apparent wing angle. One of the very best rims designed for wind angles according to the article was the HED Belgium. I got a set, the LT, built with Sapium Xray thin bladed spokes. Excellent build quality, even tension. Ride smoothness is impressive. About same weight as Open Pro onDura Ace hubs. Yet riding mtn passes in strong fall winds, the HED never faltered. It is the rim shape, perhaps combined with spoke shape, yet sublime none the less. It's the rim shape!
Follow-up question! What about "pointy" rims, eg: H+Son Archetype? Not rounded, not squared off...
ReplyDeleteI grew up and rode for decades in North Texas, where the wind is quite strong, and it's always there.
ReplyDeleteMavic MA40 rims (I think that's the right model number) and 32 or 36 round double butted spokes were always the choice. I never noticed any susceptibility to crosswinds of the wheels compared to that of my body.
You don't build wheels for the average load, you build wheels for the worst case impact. I would not recommend less than 32 spokes (3-cross) for any non-racer except for the real flyweights. A potato chipped wheel is one of the very few bicycle failures that can pretty much stop you without the possibility of a kludge fix to get home. I would suggest that your "overbuilt" wheels were actually about appropriate.
Radial spoking shows a lack of understanding of the mechanics of the spoked wheel.
It is not difficult, just tedious, to build your own wheel. I have done it many times.
I am still riding on a front wheel I bought, pre-built to the above specifications, in 1988 or thereabouts.
A pleasure to have found your blog once again after our discussion's Constance. As someone who builds wheels for a living some may think that I might know everything there is to know about wheels: I'm glad to say that I'm really enjoying your wheel (and other) posts whilst gleaning important new bits of knowledge along the way: thumbs up from a 'pro'!
ReplyDelete