I understand that the lighter guys have an advantage on the climbs, but I thought the general consensus was on the flats it was more about outright FTP than necessarily watts/kg? Put this to the test in last couple of days, a friend and I both road “Going Coastal” which only has 61m ascent in 16.7Km, so one of the flatter courses. We both road TT bikes to avoid drafting impacts. Im 77kg 6ft 2, hes around 63kg, 5ft 8. I averaged 291 Watts, he was 251 Watts, but he completed 29 secs quicker than me at 23m 22 secs. In terms of watts/kg he was around 0.2 watts/kg better than me, so it seemed that even on a very flat course the watts/kg was more important than outright power. Is that what people would expect, im not sure if there other variables to consider, im not sure even though on TT bikes with no drafting whether i could ride quicker with the same average power if applied it in a different way which might somehow be more efficient (e.g. going harder on the slight ascents or descents)? Any thoughts appreciated as i thought riding a flat course was the only way i Had a chance of beating him
Also some of these “flat” courses have little undulations that can help the lighter rider.
The average power doesn’t say what happened on those little hills, perhaps the light rider went up to 5w/kg to try and maintain a high speed and the other rider was slower at that point.
There are some discussions about it, for example here:
I am personally convinced that lighter riders are faster than IRL, especially on the flat, but also on the hills.
Equipment and pacing also play a role, e.g. in today’s TT I was beaten by a lighter rider in every power metric, but I won on time:
Me (71 kg): 321 watts (324 NP), 4.5 W/kg, 23’54"
Another rider (69 kg): 329 watts (335 NP), 4.8 W/kg, 23’56"
I’m equally fast uphill in real life on the mountain courses. But I’m also 59kg and with some reasonable power to go with it. Currently 44:49 on ADZ. Also ridden a lot of the climbs in the Haute Savoie region and further south than that - it’s my specialty thing.
69-71kg is not really much difference.
In Zwift at much higher w/kg I struggle to overtake people doing far less w/kg - so that doesn’t matter so much on flat courses.
IRL I’ve gone pretty fast on flat courses in a big peleton, sitting on 45-50km/h along Kranebitter Allee past Innsbruck Airport in 1ºC and pouring rain. That was on a Giant TCR Advanced SL1 (from 2014). I probably could have gone faster but everyone was being a bit more cautious due to the terrible conditions and we all had big climbs to do (and another 130km left) along with 6 more stages. There were some crashes that day.
Hello Anthony and fellow forumers, enjoy the graph I made above. Describing this stuff is hard in words.
As you can see from my very professional graph, w/kg at a higher weight always has an advantage on any gradient.
80kg rider at 4w/kg is indeed faster than a 50kg rider at 4w/kg on any gradient. Even really really steep ones! The difference in performance is the difference. Terrible sentence I know. Let me explain: As gradient increases the impact of pure watts decreases. However the difference here is that on Zwift specifically the performance of low weight w/kg are enhanced more than outside. Long story short: I believe a 0% gradient in Zwift has a performance equivalent of approximately a 2% gradient outside in terms of the delta between a lightweight rider and heavy rider. Meaning if 2 riders at different weights were to perform a tempus fugit TT and their own respective wattages, the delta between those equivalent performances would be reflected not in an outdoor flat TT, rather a 2% gradient outdoor TT.
He INDEED could have paced the TT better or have a more aero settup, and height does impact CDA ingame quite a lot, so there is that to consider. But the above graph does show that while outside (on equal settups and positions, etc…) you would probably be much closer in performance if not beating the guy. In my opinion.
From my low weight of 59kg, I remember having some 39kg (sigh…) rider trying to pace me at same w/kg up ADZ and I actually rode away from him.
Yup. Exactly. But the key point is you would be riding away from him ever so slightly faster IRL given the same scenario (and other equivalent settups and variables that exist in-game)
People are so obsessed with Watts/Kg that they try to use it in situations where it has little to no effect.
In Zwift (as in the real world) your CdA versus Watts is what is important on anything below about 6% gradient.
And in Zwift your CdA is based on your weight AND your height.
Your friend didn’t beat you because they did 0.2 W/kg more than you. They beat you because they had a much lower CdA.
W/Kg is such an easy metric to see (and Zwift doesn’t show us our CdA so we can only guess about what assumptions Zwift uses) but don’t be fooled into trying to apply it to flat terrain.
The question is if their contribution is similar to IRL, and I’d argue it is not. We are obsessed with W/kg because (in Zwift) it correlates so well with the speed, no matter if directly or indirectly through the CdA.
