My gut feeling is that CdA is reasonable for some standard rider - something like 70kg and 175cm.
I think that they’ve got the Cd and the A wrong though.
I think they’ve used a cylinder approximation using height and weight as inputs, but that cylinder is too upright when calculating the frontal area.
Because this makes the A too big, they’ve lowered the Cd to make CdA correct for their standard rider model.
This in turn makes changes to the height and weight of a rider away from that standard have too much impact. So taller and heavier riders go too slow, shorter and lighter riders go too fast.
And to clarify this is for solo riders. The impact of group dynamics is a whole different beast.
Wouldn’t that be down to flexibility and the bike fit/setup rather than muscle strength? I say this as a rider who doesn’t have a lot of upper body muscle strength and has match-stick like arms and typical racing cyclist large legs who is very flexible despite being some 20 years your senior.
Zwift is never going to be 100% accurate and that’s just how it is, there are likely fudges done for everyone. We just have to deal with them.
If this were a light rider complaining about something it would be just shouted down, laughed at and they’d just have to deal with it (or increase their weight as has been suggested).
Also outside rides can be influenced by many other things outside of your power and position on the bike, air pressure, wind conditions, your cornering ability, traffic light stops, etc.
Slight tangent, do you remember if bike weights are adjusted for different size riders. The really small frames are a decent amount lighter than the larger ones (also easier for the crazy weight-weenie bike builds).
If the spreadsheet of the bike data that leaked a few years ago is correct, then no adjustment is made.
It’s only a few hundred grams, in the context of a bike plus rider system where the majority of bodyweights seem to be entered at round kilo or pound numbers and aren’t updated particularly diligently, including the minor differences in frame weights isn’t going to make a significant difference.
Maintaining flat back, nose on top of bars aero position throughout a race (real life) needs plenty of back, abdominal and other core muscle strength. Not a factor in Zwift where you get whatever aero Zwift gives you no matter how you’re actually on your bike.
I can tell you as a heavy weight rider at 112kg zwift speeds are rediculously over inflated by up to 5mph faster than real life, and also the hill climbs are a lot easier on zwift than in real life (same as other cycling platforms Ive tried), and thats on top end Kickrs, v3 and v5, for comparison both trainers are watt for watt the same as my 4iiii power meters. At the end of the day you can’t expect a “game” to be accurate as it’s not real world, riding indoors will never replicate the real world, I say that as a full time zwifter who no longer can ride outdoors due to illness/disabilities.
Please stop with this argument. Even if it can’t be perfect, it does not mean that it’s not worth improving. Like saying, “what are you even training for, you’re not gonna win the TdF”. It’s more productive to think the opposite: Since it cannot be perfect, it should at least try to be as good as possible. (You may argue that it’s already as good as possible, that’s another story.)
I’ve ridden with riders similar in height to me (~183cm / 6’0") and heavier both IRL and in-game. I can drop them easily in-game, and they have no trouble keeping up IRL. I don’t know exactly where the zero-point is, but the further you get the worse the speed estimates are.
More mountain routes - the person asking when they might finally happen was told to use Rouvy instead. Or previously, new climbs only in portals with bland, boring graphics and where you can’t use the climb when you want. Not much of an improvement.
Adding more lighter robopacers (not removing existing ones). 111 votes in favour and nothing but some big arguments by a few people against it. There was even a suggestion by someone that light people should just increase their weight! How’s that for an improvement!!
Expanding the UCI worlds like Innsbruck? People instead argue to remove them.
And the other one, trying to clamp down on unrealistic power and filter it out automatically. Folks say “e-bikes okay, as long as not in racing”.
being 165cm i have a front row seat insight into how BS a height advantage can be in zwift, so i’ve spent quite a lot of time thinking about it. i’ll share the dubious conclusions i’ve reached over the years, though i am not an aerodynamicist and don’t want to overstep my expertise so let me just clarify that. i think i basically understand the issue and how to fix it, though i don’t know if it will ever be implemented. i’ll just throw these out here into the void anyway:
cda in zwift only makes a difference in specific but crucial scenarios. everyone who is sitting 4th wheel or further back is likely getting the same draft benefit or the difference is negligible regardless of how tall they are. apparently it’s unclear on whether sitting 2nd or 3rd wheel matters. i haven’t tested that myself, but other people have and i trust them enough to take their word for that
cda specifically matters when a rider is out of draft… which just happens to be during all of the important parts of any zwift race. specifically in breakaway attempts, the entirety of any iTT, or it might only occur during the last few hundred meters of any given zwift race. but in that case, chances are those few hundred meters are the meters that decide who wins and who doesn’t
the overall speed is too high, because the cda values are too low for everyone across the board, light or heavy, tall or short. when the speed is high such as during a sprint or on a descent, differences are amplified by orders of magnitude and that 10cm difference becomes a lot more important at 70kph than it is at 50kph. in a sprint, if someone is doing 70kph when they appear on your screen and you are doing 50, then you can have the best reaction time in the world and have all the power you need to win on paper, but if you didn’t know that move was coming ahead of time then you are probably going to lose that zwift sprint by seconds, not tenths
i had the opportunity to do a few road bike TTTs along with regular WTRL TTTs for a month or two a few months back and i was struck by how trivial it is to correct minor positioning errors in road bike TTTs compared to ones done with a TT bike, purely because the average speed was a few kph slower. the solution, i think, is to increase cda across the board. the speed in crucial parts of races right now is so high that it leaves pretty much zero margin for error.
i’m assuming ZHQ are reluctant to slow down the general pace, so it is what it is. in that case then my only issue with height being so important is that none us can really do anything about our height. if weight - which is something most of us have some degree of control over - affects cda then why amplify that difference with height also?
this is all just my opinion though. i’m not typical of most short, light people on zwift so i don’t necessarily have the same experience as others. but something deep in my soul tells me that weight isn’t really where the issue is. i’ll tag @Matt_Wheeler in case i accidentally said anything interesting in this non proof-read essay i just wrote because he seems knowledgeable on these things
I think that’s probably because people will be furious they can’t do 2.5w/kg 120km in 3 hours.
I also think the pace is way too fast. But there is also the question of slowing down for corners which should happen. Folks shouldn’t be taking hairpin bends on ADZ at 116km/h as I saw one rider doing a week ago.
Interesting that this rider also looked very “bulky” on the descent but rather normal and lean size on the ascent when I went past him.
Comparing my real life TT times to my Zwift ones I would say, on TT bikes at least, Zwift is quite a bit slower. I recently did a 10 mile race on Tempus Fugit and the time was around what I would expect to do on my regular club hilly TT, about 2 mins slower than a very flat, fast course. I’m 188cm so maybe just being penalised heavily for height that in real life i negate through good position?
The CDA penalty for height does irritate me on Zwift as it’s never taken into account when grouping categories, meaning you are always slower than an otherwise identical rider. Just using weight as the metric would make more sense as taller riders tend to be heavier anyway, and lighter riders naturally have a smaller frontal area in general than heavier riders of the same height. Weight is also factored into wpk obviously.
I’m also 188. Zwift has not grasped the fact that a tall and skinny person would have less frontal area than a short and stocky person. This includes on a tt bike.
If you are a capable TT rider and happen to be tall you will be faster in real life.