Should group ride organisers post rides in terms of watts not watts per kilo?

It would be nice if you encouraged ride leaders to display their weight, or to show what wattage they will be targeting during a ride. A friend of mine is only 60 kilos and will often join group D rides where, let’s say, they advertise as 1.5 - 2.0 watts per kilo. Invariably the leader goes for the higher average of 2.0 w/kg. But on a flat route, when the ride leader is 80 kg in weight, that means they are doing 160 watts. This means the smaller rider has to nearly match that (again, talking about mainly flat routes here) and now find themselves pushing over 2.5 watts per kilo to hold the group. It is very disheartening when this happens and she ends up riding off the back on her own after 20 minutes of full gas effort.

I’ve done this for five years for my ZHR Weekend Group Ride, both in the event description and during the first minute of the ride.

I’ve suggested that all group ride organisers include both w/kg and Watts in their descriptions but it’s fallen on deaf ears.

That said, w/kg is by far the best metric on Zwift, even on flat roads. But it doesn’t hurt to include both, IMHO.


Thank you for responding. It is nice to hear that at least one ride leader shares my views (in part anyway).

Hi guys, I am not here to argue. I am just trying to understand how this then works.

I am myself not far above 60kg. But in my mind, if I sign up for a 1.5-2 w/kg ride and (to use the example) the 80kg ride leader does 2 (being 160w)… then I also just need to do 2, being 120w. Which is quite far from 160 (percentage wise). Esp on a flat route where pace and constant effort is easy to control. Plus you’ll be sitting in a draft, so not even 2 is required?

Again, I’m just trying to understand how things work, so if I learn something new I’ll be delighted. But this is how I always thought it worked. Doesn’t matter much what the actual wattage is, 2 w/kg brings me as far as 2 w/kg brings an 80 kg guy putting out 160w. (Over the same piece of tarmac in the same slip of course.)

What am I missing, because obviously there’s something else…?

On a flat road, most of your power goes into overcoming wind resistance, and that is a function of frontal surface area, not weight. (Of course surface area and weight are not entirely unrelated, either.)

Tbh I would prefer an indication of target speed (on the flats), give or take a km/h or two. At least that one is clear and the same for everyone…

Hi Christo,

Thank you for joining in the discussion.

A few things to remember:
The ride leader is probably sitting in the draft too. So even if you and the leader were the same weight there is a good chance you will need to put out the same power as them. Ask yourself how often you have seen the ride leader at the front of the pack.
As Anna says, on the flat, you are mainly overcoming air resistance. If you are heavier you are probably bigger, but the air resistance and your size do not increase in a liner fashion (to the best of my understanding). This is true in real life and in Zwift. I weigh 76 kilos and did a short test with my friend who weighs 61 kilos. Same zwift course, same bike, no draft and putting out the same watts per kilo, which meant I was putting out more overall watts. In the same period of time I travelled further than she did. Which means that if she had wanted to keep my speed she would have had to put out more power. Perhaps I can can perform a test to see how much more she would need.

I did note on a steep climb recently that we both appeared to putting put the same w/kg to get up the climb, which is what you would expect as the main force you are fighting on a climb is gravity and therefore your weight.

This is all based on my understanding, which I fully admit may be wrong (I am no expert), but lets hope it starts a health debate.

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Whilst w/kg as a means for clasification is a hotly debated topic, especially in races, I’m not sure what the best alternative is. Zwift obviously has to go for the largest catch and there is probably an average weight which best represents the collective of riders and therefore w/kg works for the majority as they all group around that average weight.

Lighter riders are the outliers, as this often comes with lower absolute watts, but that said I would love to see the average gradient of rides and races and I would bet a lot of money they are largely flat meaning absolute watts would be a better system for cats.

Or maybe Zwift could look at the profile of the ride and recommend groupings based on those that have signed up!

Zwift knows your weight, height and FTP and more importantly, they know the formula they use to calculate CdA. Zwift could generate a performance number for each rider and perhaps for each course. For example, the ride could say it will be a performance level 50 (on an arbitrary scale). Your Zwift profile could then show that you need to do x amount of watts to do performance level 50.

Or, imagine this was all done behind the scenes so you don’t even see the performance level number. All you see when you sign up for the event is a personalised power requirement in watts (for example: 120-150W) based on your weight, height, the course and the leaders power. This isn’t rocket science. This is just math which computers are perfect for.


Adrian, this is awesome info in a sense. Again… I’m trying to figure this out with you.

If I can deduct from what you are both saying, you’re then actually saying the draft effect is too strong? I’m saying that because on inclines the draft effect is minor and you’re saying that w/kg then behaves “as expected” if I understand correctly.

I agree that from I’d have thought… lets keep the maths easy and stick to your 60-80 example. I’m in a draft. I weight 60. Leader in same draft, be a double or normal draft event or not, it’s same draft as long as you’re in it. In my mind, if I have to put out 2 w/kg, s/he has to put out 2 w/kg in that same draft.

One thing I have to clear up, which I found in a group ride I’ve been in recently, it was a Trek vacation or something like that ride, but I remember it VERY well for a number of confrontations that actually happened there. And this was cause for confusion on that ride.
The group leader is NOT the idiot sprinting off the front of a clearly advertised group ride. A number of people eluded to the group leader ripping the group apart… Until I mentioned that guys, the group lead is actually at the very BACK of the last grouplet, with only about 4 people behind. You are all in front of her. So, just something to add to the conversation.

Fully agree, in IRL, the big guys can suck up the air on the flats better. I’d assume Zwift to factor that in somehow. But the “how” is why I’m here…
Because in another thread, I’ve made a very clear comment/observation. And it’s been taken out of context. But, I’m struggling to finish anything but last in normal races in my cat - whatever cat that may be. But I did some TT racing for fun… So, no draft (see the connection?). Suddenly my TT races are almost pushing me out the TOP of that cat that I cannot stick to in road races. And, as you can deduct from my weight comments, I’m not IRL anything close to a TT’er!

So I’m VERY interested in where this discussion goes… (And yeah. I know I have zero Zwift race craft. I must learn that. That is not the topic.)

I’m close to 100 kg and recently joined a ride I felt would be a challenge for me. But the route was flat and I learned after the fact that the ride leader was 60 kg. They were doing the advertised W/kg but I was utterly bored after having prepared mentally, physically, and nutritionally for an all-out ride (by my standards) since the ride was at 130 W and I was expecting 175-185 W. W/kg is superb for climbs but meaningless for flat rides.

Hi Adrian,
The best way to describe the effort or pace of group rides comes up here fairly regularly. Here is an interesting thread from last summer:

I personally find that when leaders use speed on flats in the description it gives me the best sense of effort I will have to expend without worrying over the size of the leader.

For those advocating speed, I tried that in 2015. It only works for pan-flat courses where the whole group stays on pace. Otherwise, too many variables to be accurate - as a leader, I would have to give a 34 - 42 kph speed for a rock-steady 2.5w/kg ride. Speed will depend the course, the type of drafting, the type of ride, the size of the group, whether any riders are pushing at the front, etc.

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Hi Christo,

I will try to cover your points one at a time. I apologise if my previous answer was not clear, but sometimes we write things that are ambiguous to others and don’t see it, because we write from our view point…

On the subject of draft, I am not saying the draft effect is too strong. I am lead to believe that Zwift have modelled their draft very well and it is very close to real life. But I do not know how the draft helps in terms of watts or watts per kilo. I only know that its widely documented that sitting in the draft can save you 20% to 30%, and it seems to be 20% to 30% of your average watts. I will use 20% for now.

For illustration purposes let’s assume you, and an 80 kg rider are on TT bikes (so no draft from anybody to consider), and you are on a flat course. If you are both doing 2 w/kg you will averaging 120 watts and the 80 kg rider will be averaging 160 watts. But on the flat the main force you are coming is wind resistance. Let’s assume wind resistance for you is x. For your scenario of putting out the same w/kg to be true the wind resistance would need to be (you) 60kg divided by x, multiplied by their weight (80). But, weight and air resistance are not a linear relationship and so the 80 kg rider has less air resistance than this. (I am oversimplifying things here). This means less of their watts go into overcoming air resistance, and more go into actual speed. So they will travel faster and further than you. In a draft situation if you are really saving 20% of your watts, but for the heavier rider that still means they are putting out more watts, and a percentage of those watts are overcoming the air resistance, but some are left over to again make them travel faster and further. So a riders weight and their air resistance, or drag are not linear. Think about your TT bike IRL. They are heavier than climbing bikes. Great for the mainly flat courses where cutting through the air is king, not weight.

I have to say that I have no idea why you would perform better in a TT race than a standard one. As a light rider I would expect you to be at a disadvantage. IRL look at who is rocking the TT world - Phillipo Ganna. Heavy compared to many riders but just a powerhouse that can use more of that power to his advantage in a flat (ish) TT. So you, and Zwift have me stumped on that one Christo. My only suggestion would be to look at your normalised power. Perhaps you are very very good at pacing yourself and pushing out high watts for a long period. Whereas a group ride/race can ebb and flow(power surges). If you don’t match a surge you get dropped. Once dropped and out of the draft you will need to push that 20% more (the power you were saving while you were in the group and in the draft), just to stay at the pace of the pack. If you want to catch them up then you have to do a lot more. Something to think about perhaps.

I do hope you find my rambling to be of use.

Thanks Erlendur,

Nice to see somebody coming at this from the other side, so to speak.

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Good points Garry. Perhaps Zwift could give a “score” for a route, to help riders understand the overall terrain. One being dead flat, like tempus fugit, and eight being something like Alp du Zwift.

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Thanks for the link. Nice to see a recurring theme not being addressed. :frowning:

Hey @Adrian_Barlow - super answer! Definitely some points to be taken into consideration.

I have not done road racing in many years, but still yeah, I’d agree to the 20-30% savings whilst drafting. And that effect you described is exactly why we put the big guys out front when we’re on the flats! :wink: Not only does a guy like me suffer more, but I’m throwing less of a shadow for the other guys to use. Don’t know if that is modelled in Zwift as well?

The TT thing. On Zwift I entered some TT rides for fun on the day, just for a what the heck, knowing that I’d never TT IRL. And after a couple of TT rides I looked at my ZP numbers… and nearly fell off the chair. It was like borderline riding myself into next cat. ALL my red numbers were in my TT rides. While I end up more or less being the sweeper on road rides, which was fully what I expected to do having just moved up and after injury. (I joined ZP while injured from an MTB crash) So zero issues there. I expected it.

The surges/bursts etc is not what I am utilising IRL. I am an on the marathon/endurance end of MTB rider when I ride. I actually certify myself as a trail runner. And I like to climb. Not the best, but I can hold my own. Maybe I like to suffer just enough consistently (and I can plan accordingly, since there is no surges) that I somehow make TT’s work on Zwift.
EDIT: To support why I’m not doing TT, yes. Ganna is heavy - but it was a shorter ride. But same weight as Cancellara. Undisputed TT king. Rohan Dennis and Tony Martin being a bit lighter. Only light - and it’s ironic, since it does not appear that way to me - TT rider in recent years is Tom Dumoulin.

I have absolutely no idea. That’s why I’m here asking all these silly questions!

But the topic is not about my TT vs road race performance. It is about w/kg vs pure watts on group rides!

I just praise everybody willing to be a group lead. Esp on rolling terrain and a supposedly easy ride! There are guys and girls - some of them pro’s - out there doing a sterling job at this, just to be taken out by people who do not grasp the concept of group rides and relaxation.

But I really do like what you are trying to delve into here.

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Hi Christo,

I absolutely agree with your last point about ride leaders. They do a sterling job and make Zwift the great platform it is by organising the rides and making us feel like we are part of a group and not just on our own suffering in a cold garage.

But, conversations like this can help improve the platform and if nothing else help those riders new to cycling and to Zwift know why they might sometimes see themselves putting out the same w/kg as the rider leader and staying in the pack and at other times putting out the same w/kg as the ride leader and not being able to hang on.

All the best for your future rides, on Zwift and IRL.


I hear you, there are many variables on speed but I have found it to be more useful for my planning than w/kg when the leader’s weight is unknown.

I find that speed on flats at least gives me a sense of the baseline effort that will be required from me; I know I will likely have to do more on hills and a little less if I sit in the draft.

Zwift could just take the “/kg” out of the equation by making everyone on Zwift (or a group ride) exactly the same weight. Then it’d be only about watts.

That’d make things simpler.

Some people might not like it, but it’d make things simpler! :stuck_out_tongue_winking_eye: