Possibly a stupid question?

This may be a stupid question having not ever joined a race or mass event on RGT. Some rides/races list a watts per kilo level. How does this work on a virtual ride and is a lighter rider at a disadvantage. i:e If a rider is 3 watts per kilo and weighs 60 kg’s (180 watts) surely they will be at a big disadvantage to a rider who has the same wpk and weighs 90 kilos (270 watts). Outside the margins are narrowed a bit with climbs,wind resistance and just moving the extra weight of the rider along the road etc but how does it work on a virtual ride when the bike is not having to be moved and there is no wind resistance to make it a fair race for two different riders with the same wpk but at vastly different weights.

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I can’t answer specifically as regards RGT races, but it does user W/Kg appropriately for general, virtual riding in so far as your W/Kg is what will determine your climbing speed certainly and it appears to me, as a user (not developer, so just observation) that heavier riders descend faster for 0 pedal input also.
I would expect that a race where W/Kg was the deciding factor for groupings would ignore the rider weight/power output specifically in lieu of the W/Kg ratio for speed which is how you then make races “fair” for people without having to group relative to course type.

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In Zwift, wind resistance, which dominates riding on the flats and on descents, is a function of height (taller riders have a larger area) and mass (heaver riders are broader). So it’s not just watts, not just watts/kg, but in between the two, since area is less than proportional to mass.

On RGT, everyone has the same wind resistance.

So on climbs where mass is the dominant factor, watts per kg is a good predictor of speed on both platforms.

On the flats, on RGT, really watts is all that matters.


So in a nutshell, lighter riders are at a disadvantage on RGT! Also,from what you are saying the platform does not take into account the size and weight of the rider on flat so why/how on a climb is their mass a dominant factor? In the real world a 90kg rider would have to put out a lot more watts to climb as fast as a 60kg rider putting out less watts presuming they are of similar fitness. How does that work in the virtual world if their height a weight are not taken into account when they hit a climb. They could be a 60 kg rider putting out 300 watts or a 90kg rider putting out the same. In the real world the 60kg rider would win easily but it appears with my non existent knowledge of how these platforms work that the lighter rider would again be at a disadvantage? the Sorry for the nerdy questions just need to get my head around it. cheers

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Lighter riders in RGT are at a disadvantage relative to Zwift and, likely, relative to real life.

I can clearly see that where in RGT to stay on a draft on a descent, even if the lead rider is coasting, I need to pedal, if that rider is significantly heavier than my 56 kg.

Of course given two riders, one heavier, the other lighter, IRL there’s no guarantee the lighter rider will be more aero, clearly


Generally (in life and with virtual algorithms) the CdA will also go down as weight drops. Not enough to compensate, but it will generally go down. On steep hills w/Kg matters more, on the flat w/CdA becomes more important. The algorithms may or may not have been tweaked to make sure lighter riders are less disadvantaged if categories are set on w/Kg. I was certainly one of the (ahem, genuine) lighter riders when I raced on Zwift but was still at the punchy end of a lot of races by drafting etc. I’m sure the same would be true of similar lighter riders in RGT.


My view of a decent model:

wind drag is due to wheels, frame, and the body.
wheels: same for everyone
frame: proportional to height
body: approximately proportional to sqrt[ height x mass ] (cylinder approximation, constant density)

Hopefully RGT will fix this at some point.

It would be good, but at the same time RGTs physics simulation of speed seems to be massively more accurate than that of Zwift, which (IMO) is an utter mess.

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Brian Kellison looked at this on his twitch channel, coasting down a 0.5% grade in RGT. Since Crr < 0.4%, this should be possible only at a speed at which wind resistance is approximately 25% total force, and that’s what he did. The physics worked.

It doesn’t work on Zwift rides where it auto-brakes on descents (straights and corners) unless you’re in super-tuck. Supposedly auto-braking is off in Zwift races, though.

RGT brakes in corners but at near the physical limit, so you descend like Tom Pidcock, and IRL I do NOT descend like Tom Pidcock :).

hello !
To (try to) answer “the big picture”
There are only few races that are “wpkg-limited” on RGT (no categories = no sandbagging and everybody finds his/her group to fight for, which is another approach compared to Zwift, and an healthier one in my opinion).
Organizers know that wpkg “only determines your performance during a steady climb” and that, on flat, heavier riders are at an advantage if limiting per wpkg.

Thus, for the few races that I know use this limitation :

  • “Flemish for beginners (< 3.2 w/kg)” is always set on a hilly terrain, never on a full-flat course :wink:
  • The Wednesday night Omnium series are split in 2 divisions, with the limit at “3.6 w/kg or 260 raw watts” (this is especially meant for everybody can finish the scratch race, before entering the iTT. The 1st div scratch race is longer and most of the time, 2nd division riders would be DNF or have less than 1 minute to recover before the iTT if the categories were not split)

Hope it makes a bit more sense ?