# The more I think about it, the more I realize how dumb the 'height penalty' is in this game

Due to all the discussion about weight / height doping, I had to look up some stuff on the typical body size(s) of cyclists. Turns out many aren’t actually that short. Some are, but many of the top guys are actually taller than average. They’re not horse racing jockeys as Zwift would have you believe.

Height doesn’t factor in as much as riding position and even body proportions:

• A rider that can ride in a relatively aggressive position for longer easily has an aerodynamic advantage over someone 10cm (or more) shorter. Easily!
• The scale of the effect of height is so much so it seems like they’ve calculated it based on everyone riding completely upright. A short person riding a commuter bike is less aero than a tall person riding a road racing bike.
• The only calculation the game cares about is total height, not torso/inseam length. And why not (dare I go there) body width. The legs and pedaling is really what causes the most drag (apparently? but correct me if I’m wrong there). A relatively short bodybuilding would have more drag than a taller, slimmer person.

Height is one of the factors that absolutely punishes honest participants (along with weight). Worse yet the effects are exaggerated compared to the real world. Just get rid of it. It’s a game… at the very least why not balance things out to make it less advantageous for liars? Just get rid of height calc’s, and make weight give the lighter riders advantages uphill, but offset it completely for heavier riders on the downhills (would make things much more interesting… maybe).

So just punish small people instead…

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Yes it is a game and it has game Physics.

Zwift don’t know if you are riding in the drops or sitting upright. A rider can produce more power sitting more upright than in the TT position.

Zwift has to make some assumptions.

When you did your calculations what was the height penalty?

I think it’s entirely appropriate that they try to model the effect of rider size on aerodynamics. I have no firm view on whether their modelling is good or not.

Height penalty is about 1W per 1cm at racing speeds. You can easily test this yourself by riding solo laps of the volcano at constant power (using erg mode) in a meetup with no draft. Change your height and see the difference.

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Seems like a lot. Any idea what the penalty is in a draft?

No data but I’m pretty sure it must be reduced by about 25% (ie in line with the general saving due to drafting) as it’s just the aerodynamic drag term. It would be strange to do anything else.

As an unusually tall (194cm) but also somewhat heavy (81.5kg currently) rider I don’t have a problem drafting somewhat stronger riders, so long as they are not very much stronger. In my case, the weight more or less makes up for the height handicap. And it’s the hills that really count in most racing, where aerodynamic drag is small anyway. But if I was a bit shorter (with other things equal) I’d certainly be better at TTs (and TTTs).

Absolutely never said that.

Blockquote A rider can produce more power sitting more upright than in the TT position

Yes but… riders get lower on their bars at various times. And many riders trained themselves to peddle efficiently in a more aero position.

If Zwift has to make assumptions then why not flatten things out a little bit opposed to applying the maximum penalty possible?

I have to agree, being light but not so short I don’t even bother to chase people downhill in Zwift. I just tell them to go ahead and I’ll ride alone.

IRL I have no problem staying with bigger riders going downhill being on an aero bike (S5 disc) and having a fairly low position on the bike.

I don’t do racing in Zwift so it doesn’t matter much. If it changes up too much I can go back to PerfPRO where the only thing that matters is what you are doing.

How much of a penalty between Zwift and IRL did you observe.

To be honest it is just a workout after all… but I can see things being extra hard on bigger beginner riders.

At 80+ kg if you’re keeping up on the hills you’re pretty strong!

Looking at the sizes of average cyclists (from a few different sources), the average height is about 178 cm (me basically ) and the average weight is 68 kg (me again, basically…) . I highly doubt the average Zwift user is smaller than the average professional cyclist. Furthermore, many professional cyclists and Tour de France winners are over 183 cm (6’-0").

Riding position and bicycle geometry can both negate height. Lighter riders, as we know, also don’t generate the same amount of power as larger riders; there’s also some mechanical/leverage advantage - Miguel Indurain had unusually long femurs (and 180mm long crank arms!!).

Should Zwift do calculations based on height and weight? Absolutely - but at the same time, does it need to penalize size as much as it does? I think the biggest two issues are lack of being able to determine riding position and the cheating. I can get REALLY low on my drops when I need to. I think they should lessen the advantage/disadvantage if nothing else but to simply negate cheating.

You are only 3cm higher than me (and 9kg more) and asking for things to be made less advantageous for shorter riders. If I’m not fast enough, then I need to work to improve the areas where I do have an advantage.

What about the short rider who has 335w+ FTP who is also only 55kg? Such riders do exist in real life and he wins IRL A grade races but in Zwift the first thing people do is accuse them of cheating (I’ve seen the post race comments).

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To be honest if the 1cm for 1w mentioned above is true, that is not much of a penalty at all. Remember that taller riders ride larger frames, which naturally means a larger frontal area. Of course position cannot be calculated, so it makes sense that position is assumed equal whereas height is penalised.

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Zwift is a different cycling dissipline therefore it works different. Like track, road or mtb each one of those would favor a certain type of rider.

Doesn’t it depend on where on the ability curve the riders are. In a D-level event, a 5’10" rider has a 10watt advantage over a 6’2" rider, but against perhaps a 120 watt average output, that 10 watts might be significant, no?

I’m pretty sure it will scale with speed rather than rider w/Kg, otherwise its not much of an aero penalty.

Here’s the thing: A small difference in height and weight doesn’t really matter. I agree. The issue is with cheaters choosing the lowest possible height and body weight. If someone’s gonna lie they’re going to go all out. This has a HUGE effect in the lower categories as someone mentioned. People are doing this AND sandbagging. What makes things worse is that it makes sandbagging even easier to get away with: They can now put out less power so they don’t get flagged.

Also, it’s very rare for smaller riders to have high FTP’s. The short rider you mention is an outlier and w/kg over 6.0 is world class - meaning they are well known outside of Zwift. Remember that a Cat A racer can always jump down a category if they can’t keep up. Cat D cannot. Most of Zwift users (and racers) are not exceptionally rare athletes but rather weekend warriors (if even that). In real life, 55 kg and 350+ ftp is exceedingly rare, and 55kg in a pro (or even semi-pro) peleton is quite rare. On Zwift however, 55 kg (or less) is quite a common.

I mean, perhaps the physics are very realistic. But given how many people cheat, the actual outcome isn’t that realistic is it?

I don’t know. At 130 watts vs 120 watts, it would be about a .5mph speed difference. At 300 vs 310 watts, it’s about a .25mph difference; I think about 45 seconds on a 20 mile course (on flat ground)

You’re missing my point. The penalty for height is an aero one, not a power one. The penalty applies more, therefore, when travelling faster.

I was using the above tested result that was referenced of 1 watt per cm of impact to speed. Has anyone tested this at other speeds to know anything with certainty?