New CdA model!

RGT just announced that it has finally updated its wind resistance model to include body size.

Wind resistance occurs when cyclists push air aside as they ride… pushing air takes force, that force comes at the expense of power. In real life, bigger riders push aside more air than smaller riders: taller, broader riders take up more space than smaller, thinner riders. How big a cross-section riders present to the wind is described by a parameter “A”, which is area. Cd describes how streamlined they are in that cross-section, so for example a floppy jersey will increase Cd. But since we assume all riders have the same sort of kit, and similar positions on the bike, it’s reasonable to assume Cd is similar for everyone, and focus on A. The multiplicative product of Cd and A is typically called “CdA”.

Until now, everyone has had the same CdA, so the largest man and smallest woman require the same power to go the same speed. This had the strongest effect on descents, where small riders had a very challenging time hanging onto the wheels of larger riders, especially pre-steering when there was no way to stick directly behind other riders.

But now, CdA will depend on rider size. Smaller riders, as in real life, won’t require as many watts to ride a certain speed as larger riders. They will still require more W/kg, generally, but not as many as before.

This is a huge improvement, in my opinion. It allows smaller riders to be competitive on courses other than those dominated by climbs, where small riders have a natural, realistic advantage. They’ll still need to work harder than their bigger, more powerful competitors, but at least now they’ll have a chance.


Is this calculated automatically based on rider weight or is there some other setting?

They’re releasing Kickr Bodyscannr next month, you’ll be obliged to use it before every ride


And if you don’t use a Kickr?

Then you are forced into a gap between sarbacane and sarcenchymatous


“Blowpipe” and “connective tissue of a sponge” now that has done my head in
ha ha !!t

1 Like

Between those words, in a dictionary, lays “sarcasm”. My initial post was entirely filled with it.

The model, and I am guessing not speaking from any position of knowledge, is likely to be based upon assumptions drawn from height and weight. You enter your height and weight and your CdA changes to something slightly closer to real, but still not “you”.

I mean, I don’t want to be too “meh”, but it seems like it can have a value if RGT is being positioned as an official eRacing platform, which I suspect to be the case, but strikes me as having stunningly little value in any other circumstance and is actually a negative in “we spent dev time on this” at a point where loads of people are having issues with RGT anyway.

1 Like

Agree fully

Obviously it has a big effect on pack riding (the ability of smaller riders to stick with larger riders), and pack riding is the core competency of RGT.

I think changes should be evaluated on their merit, not just in software but anywhere – the “why are you wasting time on X and not Y” typically ignores the relative difficulty of doing X and Y.


It really isn’t for anyone who doesn’t want to or can’t use steering now that auto-draft was removed.

Yes, changes should be evaluated on their merit.
At the moment, for me and my colleagues who I’d spent a long time trying to get to sample RGT, the steering change has made the experience worse and this change then adds to the “pack riding” that they can no longer participate in.

I understand that there definitely is a value to these changes in some use cases, the problem is that the way they have been implemented ignores the fact that there are some people for whom they (steering at least) are detrimental and that has just been flat ignored.

I genuinely, honestly cannot understand why the old auto-draft system can’t be a toggleable option in private events.

I have gone from cheerleading people onto RGT from Zwift to having just given up on the platform completely currently, because the banding solution wasn’t perfect but with auto-draft it was workable. Now, with the steering implementation and no means of auto-draft for people who don’t want to or can’t steer the platform simply isn’t worth using…

Example: I introduced my son to riding with me in RGT. We have wildly different power outputs. Magic Roads are more interesting to ride than the built in roads, but at the same time they are visually dull. You need more riders to make it interesting, so I’d put in a bunch of pace riders with banding turned on so we could ride together.
Problem 1: If anything causes him to drop out of the banded main group, RGT doesn’t apply banding to sub-groups, so he doesn’t get tied to me to try and pull him back on.
Problem 2: With the launch of steering he also now doesn’t even auto-draft me, so I really can’t pull him back on.
So, now we’re stuck with either riding with just the two of us and no other riders on bland looking roads (he’s 10, visuals matter), or stuck on only the limited built courses and for what? There was no value to completely removing the ability of private events to have the old steering model.

I’ve given him Zwift and I use SYSTM, RGT for me is currently in the bin.


See this recently posted roadmap for steering:

It doesn’t address all your complaints but I think will improve some of what you are complaining about, especially bot behavior.

1 Like

As a somewhat lighter rider (73 Kg), I’ll gladly take these tweaks! I’ve done a few races where I can get a gap on the climb but spend the rest of the event replaying the Jurassic Park chase scene as the heavier riders claw their way back…


1 Like

I’ve seen it, it really doesn’t address any of my issues with the system and I think is actually another horrible mis-step in communication because it minimises the entirely valid complaints from, and this is key, paying users who had a product they were happy with previously.
Further, they literally go on to say “There is no intention to reinstate the old model”.

Why? What possible value is there in denying that model to people in privately created events?
I understand wanting to enforce the new model on official events, but there is no value other than sticking two fingers up at a previously happy clientelle to say “Yeah, you were happy with that, but you can’t have it anymore for no good reason at all”.

Genuinely, this whole thing has left a very bad taste in my mouth.

I’m not against the changes having happened. I am very much against the manner in which they were implemented, the communication around it and the response to the people who it negatively affected and it all seems like it should have been both so easy to avoid initially and also so easy to rectify, but we are simply being told we don’t matter.


That’s a valid criticism. That said, we can’t begin to know the underpinnings and dependencies in the code base to know if this would be easily achievable now or not. Best you can do is articulate that complaint and share it with the RGT team (and certainly you are not alone). Maybe?..

My guess is they don’t want to do what Zwxxx did, where yes you can steer, but nobody uses it, and then they leaned hard the other direction. Yeah, heavy-handed, I agree.

1 Like

Indeed, but if the alternative is, as seems to be implied in the RGT Users Facebook group, that you potentially lose up to 30% of your current user base over the change with no guarantee it’s going to generate that number of new users, it seems a bit like shooting yourself in the face…
I mean, that is a lot of people who were sat in the ether just desperately waiting for a more “accurate” racing platform…

Again, I have absolutely no qualms with wanting to turn RGT into the place to be for online racing, but it strikes me that, with sensible planning, that didn’t have to displace your current user-base in the process.

I come from a long background in the computer games industry and we’re well versed in watching companies burn themselves into the ground trying to replicate another service that already has all those users tied up.


When trying to grow market, the present market isn’t necessarily the best guide, since it’s self-selected. A nice example is smoking in bars. If you had polled people in a smoke-filled bar before smoking bans, you’d have concluded bars would all go bankrupt banning smoking.

But I agree auto-steering of some sort should always be an option.

I’ve found auto-steering to be generally a huge enhancement, however, and really adds an element to my races, which will be improved further once they allow bots to steer again.

That’s only superficially related to the CdA model, which will make for a far more inclusive playing field.


This :point_up_2: and this :point_down:

You were decent enough to put (my) sentiments into simple words, I hope the powers that be don’t reard this and one soul bemoaning the inflexible nuances of RGT but take it more as a general vibe towards the in-house virtual rising platform.

I do wish some form of poll was sent out to WahooX users with specific regard to the RGT platform, questioning use cases of said platform.

I’m sorry, but I still thoroughly disagree.
I was one of those people in “smoke filled bars”, very good friends of mine own an entire range of bars. There is no-one who would have thought they would go bankrupt by banning smoking, because smoking wasn’t the core reason they exist or even important to the core experience at all and there were loads of people who were putting up with the smoke, more in fact than those who actually smoked.

I can’t say for sure, but I would be willing to bet that there are significantly more casual riders in RGT than those who race and, with Zwift already having a lot of race series in place, not a huge pool just waiting to jump in to the platform either.
Of course, making RGT a better racing platform allows you to entice those customers across, that is a given and not really even up for discussion.

The problem is, that with your bar equivalent, it’s more akin to deciding that you want to rationalise how you ID people before allowing them to buy a drink (any drink, even non-alcoholic) and only bothering ask a couple of your mates rather than putting out any form of poll to the community. You establish that you have a driving license and so do they, so you now institute a rule that anyone who wants to buy a drink in your bar needs to show you their driving license first.
Oh, wait a minute, some people don’t have driving licenses? Well, pity, but they can still come into the bar, they just can’t buy any drinks anymore, they should go and get a driving license (I have been told, repeatedly, on the Facebook forums that I am the problem and that I should just find a way to steer).
The proposed fixes are akin to saying “Ah, there are some disabled people who can’t get driving licenses? Well, we’ll find a way around for them. People who can’t afford to drive, don’t want to drive or have any non-disability related reason for not having a driving license though, they can remain stuck”.

Again, I’m not against steering, but the means of implementation was poor, the subsequent communication and approach to remedy terrible.
It was a thing, for many years, in the games industry where publishers stopped putting money towards innovative projects, because they were “risky”, instead hundreds of millions into studios to make a Call of Duty clone without at any point realising that CoD (and Battlefield to a lesser extent) already had that market cornered. They lost millions, studios folded, good projects never even got funded and the Publishers were convinced that the market was just contracting. It was genuinely insane and short-sighted decision making.

It sounds like I’m really grumpy with all of this, and I am, but only for what in reality are very small decisions that could be easily fixed.
Actually, that is what makes me so grumpy with it, the fact that the problems could have been so readily avoided and could still be so easily fixed.
Why was there no community engagement first, to establish how important steering might even be, or how many people would be impacted completely negatively by it’s implementation? Why were no processes in place to mitigate problems for people who couldn’t use steering? Why is there such antagonism to even acknowledging people have issues with it?

The single thing that really drove me off RGT fully was not that the platform had become significantly devalued to me (though that was going to do it ultimately, the current solution has literally no use to me), it was going to the various RGT forums and repeatedly being told that the onus was on me to find a way to work around a problem that simply didn’t exist for me days earlier and completely refusing to even acknowledge that even if I could/would steer, I still simply don’t want to.
And, finally, again, the biggest problem with this from a consumer perspective is that this is not an Alpha or Beta release only affecting people who want to test it, it is the live release of a paid product which has turned something that people are tied into paying for into something they no longer want to use!!!