I am a bit of a Zwift racing fan boy. Thanks to growing up and holidays, I have recently gone from 150ish lb to about 160ish lb., 10lb heavier. I get that there are Zwift hackers who put their weight extremely low and go super fast. But for your average guy, does 10 lbs matter that much? For example, I can usually hang on to A bike up medium to light hills that are 5 minutes or less. Will a 10lb have me out the back dropped harder than a rock? Will I see any benefits? I was a great sprinter cause I could hold 800w for 15 seconds, which at 150lb was like 13wkg. But now im 10lb heavier, will my sprinting suck even though I’ve upped my wattage a little?
Also what about hight? I am growing taller, but that’s obviously slow. Is that a big deal? Is that ok to set at the start of the year and forget, or should I measure myself quarterly?
ZwiftInsider has a bunch of articles on this. In general, it matters, but that much is a that depends.
I find that W/KG in Zwift matters a big deal in racing, so there is an edge in cheating your weight. But does it make you from category B to A? No. I think the weight can matter in decisive moments, less so when you’re trying to hang on with the draft, assuming equal power.
Unless you want to win an official championship, I would just change it every few months. I fluctuate 2-3 KGs during a year, and I know if I am doing really well even though I am a bit heavier than advertised, I keep it in mind for myself. And the opposite.
Zwift is all built around w/kgs, and 4kgs (10lbs) is a bit of weight, but it isn’t a huge change. I don’t think 10lbs will suddenly mean you get dropped on a climb, but it might depend on the length of climb and what you can sustain.
Sprinting at 800w you are talking 11.1w/kg vs 11.7w/kg.
Climbing at 300w that’s 4.1w/kg vs 4.4w/kg.
So it’s not nothing. If it was a long sustained climb and the front is holding 4.4 you might slowly drift back. If you are bit heavier but can put out more watts then you would probably stay in touch.
Yes. If you make sure you have the correct height and weight before every race then you can a) know you’re being 100% honest and accurate, and b) (for weight) look back over your own data at the end of the year or in 5 years and know that you’re comparing apples with apples.
Otherwise, you’ll look back and not be able to be absolutely sure that your wkg PRs are legit, and so can’t be sure if you’re progressing.
I like to use Zwifter Bikes to see how things like this can impact a race. Select a route with a climb you’re interested in, or just find a climb based route. Click over to “Bike” and increase level and drops to get you the bikes you have available. Click over to “Rider” and input your stats, and what power you want to target on the climb. If you click the little drop-down arrow on a certain bike/wheel combo, it’ll break the Zwift route down by segments, where you can find the time for a certain climb. You can also include bike upgrades there.
For an example, take Volcano KOM segment #2 (first climb, 1.1km at 3.8%), level 40, SL8, Enve 4.5, 175cm height, 300FTP (though I don’t think FTP matters since you put in average power).
Assuming 380w average for the climb, it takes 2:10. At 73kg and 380w, the climb takes 2:15. To match 2:10, you’d have to put out 400w. Unfortunately 400w is the limit for the website, so you can’t use it for short super punchy sprints, but it at least gives an idea for longer climbs and segments.
For rollers and flat stuff, the weight increase isn’t going to matter much since raw watts trump w/kg on the flat stuff. Flat sprinting in particular is going to have very little effect. But 10 extra lbs can make a difference any time the road goes up hill for a bit.
I don’t really monkey with my weight in Zwift, it probably hasn’t been adjusted in 3 years. My zwift weight is understated during the off season when I put on a few lbs and is overstated when I’m around race weight during the season. I don’t do a lot of zwift racing, it’s mostly just group rides (particularly in the off season). Years ago, I did a lot more zwift racing and was pretty diligent about keeping my zwift weight aligned with my actual weight. Which is an entirely different set of moral questions - does it need to be what I weigh as I’m jumping on the bike for a race or can I use the lowest weight I’ve seen on the scale in the last week? I assume for the serious racing in Zwift, it should be rider weight just prior to starting the race (I think that was the rule when they were doing organized racing at one point with pros and elite amateurs).
Note that the power input in ZwifterBikes is not strictly limited to 400w, only the slider is. If you want power values up to 1500w you can put that in manually (click the little pen icon next to the rider detail sliders). Just be aware you may then push the parameters of the physics model a bit out of the normal operating range.