Zwiftpower Category Power Thresholds

Hi Racing & ZwiftPower community, I was interested in whether anyone knew what the background for the power thresholds on the categories were, and had an opinion on whether they were worth encouraging the powers-that-be to revisit.

For example - Cat B begins at 3.2w/kg only if you are over 200w. Why 200w? Why not 250w, or any other number, for example?

Disclaimer: I am a lightish rider who wishes that was higher.

If I use myself as an example - I’m 72kg with about FTP of about 3w/kg, so if my weight stays the same then the very highest my “FTP” (I’m crudely using this to mean 95% of top-3 20min powers in the last 90-days) will ever be allowed to get to in Cat C is 3.2 x 72 = 230w.

Of course in my category there are many heavier riders and on a like for like basis they appear to win the lions share of the races. So someone who is 90kg and 3.2w/kg will be able to reach an FTP of 288w before they get bumped up to the Bs.

But in the meantime, they will always be faster than me even with the same w/kg. Even up the Alpe du Zwift of all places (albeit its only a smidge faster there)!

On the flats though it is really significant. Please head over to ZwiftInsider and read the “SPEED TESTS: STEADY W/KG ACROSS VARIOUS BODY WEIGHTS” article if you’d like the background and analysis to the maths below.

Even if the results-based-categorisation that Eric at ZwiftInsider dreams of is still some distance away, why not just readjust the watt limits so that there’s a more even distribution of people’s weights in the winners of Cat-C races?

I mooted 250w above which would mean that the likes of me could then get to 3.4 w/kg and still be in Cat-C. This would give me an advantage on the climbs and reduce (but not eliminate) the advantage of the 3.2w/kg 90-kg riders on the flats.

Using Eric’s maths - and these 2 example riders at 3.2w/kg.

On the flats, today their additional power at the same w/kg means that they go 1.6kph faster. Eric goes on to say that each extra w/kg gives 4.4kph. So if the max wattage limit was raised to 250w, and that allowed me to be 3.4w/kg then I would be 0.9kph faster than before (provided I could up my power ;-)) but still 0.7kph slower on the flats even with the 0.2 w/kg rating.

On the climbs of the likes of Alpe du Zwift then an extra w/kg is worth 3.55kph so my 3.4w/kg vs the 90-kg rider’s 3.2 w/kg would make me 0.7kph faster.

Overall - when we are both at the same position in the category - in this case at the upper limit - there is a more level playing field.

I certainly do not seek to swing the advantage in the other direction, wining a tough competition is so much more satisfying than an easy one, and I entirely recognise that there will always be physiological advantages to those who are bigger or stronger in sport. There will also be still the impact created by how hilly a circuit is, which could then play a much bigger part in who benefits most, surely not a bad thing either provided it is balanced?

I do think there might need to be some w/kg limits too that trigger upgrades even irrespective of weight - especially with the advent of the strong kids who are coming through the ranks - 4.5 w/kg in Cat C might mix it up a bit too much.

It just seems to this lightish Cat C rider that there might be an easy way to have a categorisation system that provides a more equal opportunity for more to win than the one that exists today provides.

Is this not worthy of investigation given all the data must be there to come up with a “calculated” Watt limit thresholds to join the w/kg limits?

I’ll continue to ride and race for whatever positions I’m capable of … of course I’d love to see that as I get to the top of Cat C limit (my goal for this year) that I could have a more equal chance of victory, hence my open disclaimer up front.

My final card to play to suggest that this could be worthy of investigation is that this would surely then also further equalise the playing field for MIXED races such as the Zwift Racing League (which has enabled this for season 2) and already exists in the WTRL Team Time Trials; given the average lighter weight of women than men.

I hope the above provides some calculated thoughts for discussion and thanks to everyone who takes the time to read it and offer their thoughts.

I would think a ranking system based on performance would fix most of your concerns.

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If anything the power thresholds need lowered. I’d suggest by 10-20w

Look at all the kids and light riders smashing the lower categories but avoid promotions to a league they are easily capable of racing in.

I think more of the issues is the majority of races on zwift are not what i’d call hilly so in that sense lighter riders are at disadvantage. Have you tried racing something like mountain route or laps of whole lotta lava to compare?

Interesting - thanks for the link @Gerrie_Delport_ODZ. To be honest I think that would be great too - I was just seeking maybe an easier way to achieve a stepping stone in that direction. Seeing the positive reaction to that other post, at least there seems a strength of feeling about it. What’s your view on why nothing’s moved forwards yet?

Hi Gordon - I’m racing in the ZRL at the moment where there’s a mix this season. The problem is on hills the lighter rider with the same w/kg are still no faster - so any time there are flats the lighter riders can drop off with never any upside.

I totally understand about the kids racing too - and although mine are too young to race now I hope they will one day so like that they are encouraged … however I agree that there maybe should be some banding so that a 40kg rider at 4w/kg would still be a B rider and not destroying all the KOMs in their wake in Cat C?

All the data has to be there for Zwift & ZwiftPower to analyze it and work out the right levels … I just don’t understand why they wouldn’t do it.

I really don’t have any inside info but my personal guess is there is a lot of work on the back end and Zwift is ramping up staffing. I don’t think Zwift understand how big Racing is, they look at number of racers but that does not tell the whole story.
Like I train 10 hours a week to race one hour, but if I don’t have fun in that one hour why would I train 10 hours on zwift?

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All the data is there. I just think keeping zwift running is more the priority with user numbers doubling in the last year.

Very frustrating really as it’s only an excuse for the last year and we have been racing with similar issues for years without much progress being made but fingers crossed something is done to try improve zwift as a racing platform or more users will start to look elsewhere.

ZRL this season is an interesting one. id suggest we have not really hit any hills yet.
It will be interesting to see your thoughts after innsbruck afterparty should mix that up more and whole lotta lava later will be one for the clmbers also.

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I think the problem there is not so much the w/kg numbers or wattage caps, but the faulty algorithm Zwift is using in terms of speed calculation for very light riders. The “Zwift speed” of a 30kg 10 year old is well beyond what they would be doing IRL. This means the “smashing” they’re doing is a product of bad code; If their Zwift speed was a better match to their true IRL speed this issue would go away. Presumably there is good real-world data out there that could be used to generate a better algorithm pretty easily.

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