Bruni's kits made of Dyneema fabric (abrasion resistant, water resistant & flexible) are being used for aerodynamic advantage on the World Cup circuit. Should they be considered an unfair advantage?
They break the rules of competition per another post regarding fit. But with the material being a one off (made of an Oakley-esque Unobtanium material) suit, I pose that it is an unfair competitive advantage.
Dyneema, in this application, behaves as a skinsuit, staying tight to the body (many report of Bruni being PULLED into his kit) & most importantly blocking wind's ability to penetrate the material to increase drag on underlying surfaces like skin, baselayer clothing, chest protectors & all other forms of body armour.
My best comparison is a car with a radiator vs a Tesla.
Looking at you science types out there. Fire away.
Did his suit beat Jackson in Leogang and thus...the title?
1- Dyneema has pretty much no stretch at all, this is also one of the reason it's a good material for rope, sails, bikepacking bag and many other use but not for clothing. I am very dubious of your claim that Bruni kit is made 100% of Dyneema. There can be some of it for added abrasion resistance like other some other clothing company are starting to do.
2- Dyneema and other UHMWPE fabric and material are available for purchase by normal people without having US government security clearance. https://ripstopbytheroll.com/collections/dyneema-composite-fabric/products/0-51-oz-dyneema-composite-fabric-ct1e-08
3- For Bruni tightness of his kit, that is up to the UCI commissaire but yes his kit seems tighter than most other riders. Still a 2 piece kit that is allowed by current UCI rules.
4- Windproof quality of a fabric doesn't make it more or less aero. Human skin already act as one big non-porous object to the airflow. So your analogy with a Tesla and a regular gas car doesn't work here.
5- Bruni kit could be made of hemp but with the same tightness and it would still be more aero than someone riding with an un tucked jersey and a size too big pants regardless of fabric choice.
6- Yes it's possible Bruni's tighter kit could have been the difference between his time and Goldstone's time. But then again, Goldstone is smaller than bruni so he inherently have a smaller CdA to begin with. Wind speed condition might also have been different between Bruni and Goldstone run. On a track like Leogang with two key speed section, a wind gust or just less headwind or more tailwind could have made some difference. How much of a difference ? hard to know without knowing some actual verified CdA coffecient.
7- Downhill racing airflow should be very turbulent and hard to model unlike track cycling that has a much more controlled environment. So making aero decision and impact is much harder.
8- Some team have done in the past some wind tunnel testing but as far as I have seen this has been mostly to find the most efficient tucking position which should result in the easiest attainable gains compared to equipment choice.
9- If skinsuit were to be allowed in DH, we would more likely see tripwire and ribbed fabric instead of smooth fabric like dyneema and even specific skinsuit for the different average speed of each track. Aerodynamics doesn't behave the same way it does at 35kph (much more turbulent) and at 70kph (getting more laminar). This is why road and track cycling have different skinsuit for different events. Castelli make a skinsuit for speeds below 45kph and another one with different fabric and seam placement for speed above 55kph.
Jersey
The jersey shall be a long-sleeved shirt whose sleeves extend down to the rider's wrists. Jerseys used in downhill events should be of a type specifically designed and sold for use in BMX Racing or Mountain Bike downhill events. Jerseys designed for road cycling, skinsuits, or one piece suits comprising the jersey and the pants/shorts are not permitted for use in downhill events. The jersey must be either close fitting around the waist or must be tucked into the pants before the start to not cause interference.
Pants
Long pants or short pants combined with suitable knee and shin protection are authorised. Such long or short pants should be of a type that is specifically designed and sold for use in BMX Racing or Mountain Bike downhill events. Long pants of the type described above must be of one-piece construction and made of tear-resistant material. They should cover the entire length of both legs until just above the shoe or ankle. Short pants of the type described above must be of one-piece construction and made of tear-resistant material. They should be worn together with suitable leg protection, that covers the entire knee and the entire shin until just above the ankle.— UCI-4.3.011
‘Here at the UCI we look at the changing trends and adapt the rules accordingly. Full motocross style clothing has become an outfit of the past and the clothing is now very fitted and streamlined. As a result, we have decided to erase the rule that dictates that clothing cannot have a lycra-elastane base, specifically for the World Champs.’ Johann Bloggs, UCI Spokesman.
It seems like all they care about is that the Shirt and Pants are 2 separate pieces of clothing.
as if J.Goldstone is wearing JNCO’s and a fur coat? Everyone is racing in mega tight gear…maybe Bruni had to be forced into his race uniform because his legs are 30” around! (Speaking of which, did you hear him say he’s looking to lose 25 pounds in the offseason?)
rumor times has got to you Bizutch, go soak in a hot tub or better yet go astral projectile style in a float tank…this is too much!
Also: Johann Bloggs is definitely a fake name.
I totally think leogang is won or lost on that one section - but I expect Bruni has a lot more in his favour than just the clothing material. He knows how to tuck properly as well, and its not like Dyneema is the only material you could use so its more like did Jackson leave speed on the table? Considering how little aero testing teams have historically done, there is a ton of low hanging fruit those guys could have dealt with but chose not too. So I don't think its an unfair advantage, and I hope theres more of it!
my s-works shoes are made with dyneema
i am very fast!
Bruni's kit is not made from Dyneema, so your whole argument is stupid.
The question is worded incorrectly:
Does Bruni look cool as shit riding his bike? If yes, then we are all good.
I can't remember which video this discussion happened in, but someone was complaining that Bruni's team have an army of line spotters using dedicated timing equipment. The man-power, equipment and analysis make this completely out of reach for most teams and results in Bruni and Finn having much more info than others on the best lines. I would call that an unfair advantage as it is using elements and technology outside of the track for a clear advantage.
was going to ask the question of how one would know his suit is dyneema. is there a source, bizutch?
(not at all) Vital-Raw-Smells behind the scenes shot of Bizutch inspecting bruni's race suit.
I believe that technically dyneema was first used in bow strings by a Japanese company that calls it Angel Majesty. But yes it's also used in sailing. The company is local to me and I worked there for a while splicing rigging for them. It does stretch, but not very much. We used a truck winch to stretch finished lines until it exploded one day, then we switched to a hydraulic ram.
To be clear, I'm not insinuating Bruni is a cheater.
On of the podcasts early this year clearly stated he's got a stupid expensive Dyneema kit.
But let's assume the podcast w/ World Cup racers on it were wrong.
To address what @1llumA , Dyneema not reducing drag more on the human body is definitely plausible. You said yourself road teams have materials, patterns & construction for TWO forms of road kit drag.
Protection the rider wear have tons of holes, voids, vents & soft or semi-porous surfaces.
Racer w/ a Fox or TLD chest protector, rib pads, elbow & forearm pads, knee & shin pads...that's 50% of surfaces facing wind. ALL create drag if you put them outside of or even under a regular ventilated jersey.
Place Dyneema on those areas of kit...big reduction in surface drag.
In reference to "buying" Dyneema, I'm talking about a kit being required to be available to the public. If a racer is wearing a kit that is insanely expensive to manufacture that gives an aero gain, then it should be available for sale in some quantity to racers?
And as far as wind tunnel testing, the big S kept a link hidden for 2 seasons. You think they're gonna invite us to aero tests?
If I wanted to aero test DH clothing, I wouldn't do it in the tunnel. I'd just do no pedal (not chainless though) runs all day & aggregate the data. You'd know pretty fast.
And you wouldn't tell your competitors. Heck, you'd LIE to your competitors b/c there's no rule against it.
I literally had to look up the material after listening to the podcast talking about Bruni's Dyneema kit because I had never heard of it.
You in the S design department?
I don't care about Loic's skinsuit, I want to know all the magic Ohlins have going on with Loic's suspension.
Agreed. I was going to say that a remote compression adjuster for your fork and shock could potentially save you as much time on the middle section of Leogang as an aero suit.
I tried to keep my explanation simple but it seems my message is not getting across.
Aerodynamic force is calculated as such:
Fd is the force created
P is mass density which in Downhill racing will vary slightly based on atmospheric air pressure of the day but is relatively constant
U is the air speed and it is squared so faster speed will exponentially require more energy
Cd is your drag coefficient which varies depending on reynold numbers so your drag coefficient at 35kph is not the same than at 80kph because lower speed will have more turbulent airflow and higher speed will have more laminar airflow.
At lower speed / higher reynold numbers airflow seperation is less of an issue so fabric aero properties/seam placement is less important.
A is the frontal surface area that airflow see.
Surface area is the easiest place to make aero gains and can be done with just a good camera and some software to compare 2 position.
A flappy garment regardless of fabric choice will always create more aerodynamic drag (aka slow you down or require more energy to go at the same speed) than a skin tight garment with no wrinkle or flappyness because it is increasing the surface area.
Starting from a skin tight garment, you can then work to optimize your aerodynamic drag by adding trip wire and ribbed fabric to reduce airflow seperation. That is the difference between a regular road racing skinsuit (designed just to be tight to work well at slower speed) and a TT skinsuit designed for higher average speed to reduce your Cd
So if your dyneema garment is still flapping around in the wind which is the case for Bruni's kit then it's not more aero than a regular polyester/lycra kit of similar tightness because they have the same surface area.
Body protection do create more drag but not in the way you are thinking. Air flow around your kit. The small amount of air that goes through does not matter in terms of aerodynamic drag. Body protection increase the surface area that is facing the airflow and therefor increasing drag.
Because Dyneema has little stretch, a kit with a high percentage of Dyneema would actually be hard to be skin tight or would be hard to move in.
So should the UCI ban rider under 5'5'' and 65kg because they have an unfair advantage of a natural smaller surface area ?
TLDR; Bruni kit being made of Dyneema or regular polyester/lycra mix does not matter. The tightness of it is what could give him an aero advantage.
If specialized is using Dyneema in Bruni's kit it is most likely for abrasion resistance in key place where such event could occurs like forearms/shoulders/knees much like other brand using cordura or other similar fabric for the same reason. Dyneema would just be lighter.
i'm into hammocking as a lifestyle and they're hyped on dyneema ropes and ridgelines...another reason you need to chill out Bizutch. Get yourself a hammock dude they're the best this is all making sense
Don't let your appreciation for SuperBruni's physique cloud your research into the dark arts of aerodynamics...like, taking the tailgate off doesn't make your truck get better gas mileage. It sure seems like it would but it don't. Maybe Jacko's running golf ball dimples and they're even faster than the smooth man (he is SO smooth!)...
anyways yeah I voted no, but I did hear a podcast last year where dude said the skinsuits were like 3 seconds faster per km back in the day so for sure it's possible...maybe it was with Ben Cathro? I dunno.
Bruni wins though. He's the king.
downvoted because how dare you
It was Cathro, and iirc he said ~1 second/minute
Found it: "Those things were faaast! We calculated that the suits were worth about a second per minute of track which saved us five seconds total over a race run"
Source
A second per minute is a crazy competitive advantage. For a top racer that's the difference between training or sitting on the couch for the offseason.
And GMBN in their not really scientific testing had a 5-6s difference between baggy kit -> normal DH kit with no protection underneath -> TT skinsuit on a 4 minute trail.
Bruni telling all these guys their mustaches look great, climbing the results sheet with every one…
Thanks for the carefully thought out and insightful comment!
The OP may be mistaken. But Fox did use dyneema knee sections on their Defend pants a few seasons back. Maybe starting in 2018?
Bruni's kit is made of the usual polyester, elastane and cotton blends. Not dyneema.
You maybe mistaken, or confusing dyneema with Alcantara, a faux leather material that Bruno uses in his gloves and was mentioned in podcasts last year
The wind tunnel testing they do in the video is probably as 'scientific' one could get with measurements at this point.
I don't know where dyneema is thought to be in Loic's kit, but at 3:07 in the video you can see him stretch his pants pretty far which would suggest those aren't made with it.
I would also guess that if dyneema were such a huge advantage, before it made it's way into MTB we would be seeing the top GC riders with dyneema kits at the Tour de France but as far as I know they do not. I can't find anything representing exactly what they wore but other skinsuits are just typical jersey/athletic materials.
Sorry for not remembering which DH pod the Dyneema kit mentions came from, but it was this year. It was either The Ride Companion, Moving the Needle or Downtime Podcast. They made a specific mention of the material, of how expensive Bruni's one off kit was b/c of the materials used.
And @1llumA big props for doing exactly what I asked, fully nerding out. You make way more sense about these things.
So the weight of a rider is an interesting thing too. How do they account for rider weight/mass, their girth or surface area fully padded up and the other variables in the wind tunnel or with software?
Is there a certain amount of body weight that essentially neutralizes so many square millimeters/inches of surface drag?
@TEAMROBOT that Cathro interview was another factor that interested me. A full second per minute. Getting to make 3 seconds worth of mistakes on a World Cup track & still be dead even w/ your competitor really is massive.
I'm still picturing stretch materials that are at least DWR (Durable Water Repellant) as having less drag than a lycra jersey because of all the microscopic holes. I've not handled Dyneema so don't how it compares to all the stretch DWR gear out there, but in my mind's eye, I picture both to be able to prevent wind penetrations and decrease drag. I'll get over it.
But man...this stuff is fascinating for my simple mind.
I hate to say it but Bizutch is correct, I listened to the same podcast where it was mentioned that Specialized is using Dyneema on their Team kits for more abrasion protection. They're not on Fox apparel for years.
My fox reference was because it's easy to get confused between brands/riders etc..
I'm well aware Bruni et co are now on S kit.
The OP claimed Brunis kit was 100 percent dyneema for the purpose of aerodynamics. Neither are true.
Having dyneema fibres woven through the polyester/elastane fabric makes sense. As does having dyneema portions/segments or Cordura as some brands use.
Anyway long story short if there are dyneema fibres in the S kit then it's for abrasion protection not aero advantage.
This forum is gonna implode once brunis Electronic damping mode selector is released to the public 😂😂
Oh boy. Besties!
Rider weight - it's not that simple, mass is not a factor in the production of drag.
If you were in freefall (imagine a skydive), an increase in mass would increase your terminal velocity downwards, assuming drag force doesn't change.
It's all a bit pointless to compare as a heavy rider is probably also larger (likely increasing drag force), but they may also be stronger - meaning they can pedal harder, etc. They'll also have more momentum, meaning it's easier for them to maintain velocity.
All these variables pushing/pulling against each other is part of what makes downhill such a unique sport, and why we see someone with Laurie/Jackson's physique winning one weekend, and a Minnaar/Coulanges' type the next. There is no perfect.
DWR - I'm not sure what you're getting at, water repellency doesn't directly reduce or increase drag coefficient.
Imagine a sail on a boat, a windproof material in that scenario will increase drag (making the boat faster), an air permeable fabric will do the opposite. DWR doesn't directly fill holes/reduce permeability, it makes a rough surface smoother (meaning water beads off due to reduced surface tension). This would (maybe) have a (very small) effect upon a drag coefficient but I'd be blown away (excuse the pun) if it was even measurable on a rider in a wind tunnel.
Riders wear tight, stretchy clothing to stop their clothing 'billowing' - which increases cross sectional area, and drag force. If a non stretch fabric was tight enough to not billow, it would impact a rider's mobility significantly I'd have thought.
A non-stretch, windproof fabric would likely make a negative change.
I say 'likely', because non-steady state aerodynamics are extremely complex, and I'm not sure a marginal wind tunnel gain would even be evident in a real-life DH run.
The relation of body weight/ surface area is relatively simple as a lighter rider would be physically smaller so lower surface area but gravity also play a role which favors heavier rider. So theoretically speaking the heavier rider have a lower top speed due to more aero drag but can get to that speed faster via gravity force. And vice-versa for the smaller/lighter rider.
As for Windproof/waterproof fabric microscopic holes being more aero that is not the case, they still act like a smooth body like polyester/lycra fabric. Ribbed fabric and trip wire used on road/tt skinsuit are not microscopic in size to be able to affect airflow.
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