Why W/kg?

So I’ve tried a few rides/events, and it feels like when a ride states that it’s going to be a certain w/kg range, say 1.5-2.0, that when it says those around me are going 1.8 and it says I’m going 2.3, I still get left behind. If your speed differs at the same w/kg because everyone’s weight is different, wouldnt a target speed be better to keep everyone together? I weight roughly 60kg, and I find myself usually far behind the pack, going 2.5 w/kg but not able to keep up…it just doesn’t make sense to me…im new to biking in general and have never done any form of cardio training or bike/leg training for long distances.

Generally it’s a good idea to understand the weight of the ride leader. If they are quite a bit heavier than you, you’ll need to put out a bit more to stay in touch.

I think it’s generally easier (and I’m fairly light) to pace yourself on w/kg rather than speed.


Hi @Jonathan_Bautista1, welcome to the forums.

What type of bike are you using in game? You want to avoid TT bikes, they don’t get the draft benefits. Gravel and mountain bikes are slower on pavement due to higher rolling resistance ( but faster on dirt than road bikes).

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I just started so I’m using the standard Carbon bike, similar to my actual bike in Real life (Giant Escape 3)

Hi @Jonathan_Bautista1

Are you referring to “The HERD Rehab Ride”.

Oh I did that on Saturday, was perfect for my first ride, kept up with the pack and even inadvertentlywent ahead a bit (whoops). It was my first group event so I’m not great at keeping pace well yet with others if they are going slower than my pace (gotta work on that). I tried a couple others yesterday, but couldnt keep up even though it said they were going 1.8 and I was going 2.4 and couldnt keep up. But it’s to be expected since I haven’t been riding very long.

On a positive note, completed my second ride today and upped my ftp!

Always worth trying to stay just in front of the leader, which will give you the best available draft and hopefully won’t feel quite as hard.

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I don’t know what your current FTP is but my suggestion is to select group rides that will keep you in the blue zone. That is FTP/2/weight.

So lets say your FTP is 130w and you weigh 60kg. Then 130/2/60 = 1.1w/kg that will be the group ride that will be the most fun and if it is slightly faster you will be able to keep up.


Ftp rn is 107, im just starting biking so it’s super low, was 92 on Saturday so today’s ride def. Bumped it up. Ave wkg went from 1.5 to 1.7 so I’m proud of that, and did it while not in the pack, so did it mostly solo. I guess being behind helped motivate me a bit to not fall insanely far behind. Mainly didn’t want to be lapped


Jonathan, there are many factors at play. On a flat road or on downhill, the key parameter is power. Watts/kg are less important than watts. This is because you roll on wheels, and your weight on a flat does not make that much difference (other than higher air resistance if your are fat). Heavy people tend to generate more sheer power, but still have relatively low watts/kg, due to their weight. On a flat, they can do well compared to other riders because of their high power. On a climb, power no longer as important as watts / kg because one has to haul their body weight up the hill and this requires energy. A lot of energy! So, light riders might have a modest absolute power, but very good watts per kilogram, and will excel at climbs much more than on flat roads. Finally, there is such thing as drafting - if you are behind other rider, turbulent air flow created by that rider reduces your air resistance, and you can ride at the same speed at a lower power.

Your weight is more or less what it is. It is unlikely to change significantly. You power will, with training. So watch your power, and do not worry too much about watts per kilogram.

Another consideration is your bike and wheel choice. As a beginner you will be riding with people who have faster bikes and wheels: either more aero on flat routes, or lighter on climbing routes. The Zwift Insider shopping guide about what to buy at each level can help you pick the best performing equipment available to you. I do mostly shorter rides so I don’t collect a lot of drops. I used the Tour of Watopia rides to increase my level as quickly as possible. Now at level 14, I have collected the DT Swiss ARC 62 wheels and a Cannondale Evo for climbing routes, and the Zipp 808 wheels and Specialized Allez Sprint for flat routes. These choices fit my small budget and help me hang with faster riders with less effort. ENVE SES 3.4 wheels are also a good choice for climbing routes.

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I randomly noticed this result, and looking at the stats, it’s perhaps difficult to figure out why the 4th place finisher didn’t come in 3rd or even in 1st. This was a flat course for the ToW. Needless to say, other things are going on that contribute to actual placements:

John, in that case - they were all riding as group, they finished within 3 seconds. It’s entirely possible that the other 3 drafted “Hans Gruber” for the entire race. Drafting makes a huge difference.

In racing, people put WAY too much into avg power.

In Zwift, w/kg is still significant on the flat, as a lighter rider will also have lower aero resistance - Zwift uses height and weight to calculate frontal area. A lighter rider will have to generate more w/kg than a heavier rider, but the w/kg number is normally far closer than watts.

Indeed you’re likely correct, and drafting is certainly one of the “other things” I mentioned that can impact performance. Typically I don’t think you don’t see a full 1 w/kg difference though on the entire ride and see times so close, especially as 3 out of the 4 riders were all almost the same weight. Anyway, this just grabbed my attention as a good illustration that there are many factors other than w/kg that can have large impacts.

ToW rides aren’t actual races, so there’s no way to tell what people’s objectives are: riding it as a race, having an easy ride, doing a free ride workout… who knows. Rider 4 might have decided he wanted to treat it as a TT workout without particularly caring where he finished while the others were riding for finishing place so just sat on his wheel. Maybe rider 4 felt he’s much stronger than the others so it would be nicer to let them go for the finishing places. Any number of reasons are possible.

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Sure. Lot’s of maybe coulda beens. The point is that there isn’t a slam dunk predictability that the best w/kg (or even else just the most watts) will cross the line first. Maybe, just maybe, there’s a skill in riding style that comes into play as well.

That and in something like a ToW ride whether everyone at the front is actually trying to finish first. Many simply aren’t, even if they put out way more w/kg or absolute power during the ride than others.

Of course, but isn’t the first question why the rider with a +1w/kg on the ride wasn’t way off the front 10 minutes into the ride?

He was probably on a TT bike. and did not care to ride in any draft or he was a bit late and sat in the pen while the others was already riding. But as many have said this is a group ride where people have different goals.

Sure, but this isn’t about goals, but about whether straight math determines who will prevail. This is just an illustration that the numbers won’t always provide a clear answer as to why the result of any given event is the way it is.