bblair

Riding a trainer gives one plenty of time to think about useless stuff.

On a flat route, it seems that power output (watts) is way more relevant than W/Kg since you are not dragging weight up a hill. Just wind resistance, rolling resistance and other minor things. So, wouldn't it be interesting to see what other riders are putting out as they fly by?

I can change my listed weight to 10kg, which might help me uphill, but my pathetic 130 watts would still get me dropped on the flats. Rightly so.

bblair

No interest, huh?

Today I rode TDZ stage 3 which was a pretty flat lap around New York's Central Park. I'm humming along at 2 w/kg, which for me is about 140 watts. A huge pack comes flying by and I notice that most of their outputs was not much higher. A rider weighing 50lbs higher could put out 185 watts at the same W/Kg and go flying by on a flat course.

base2 

If a huge pack went by at nearly the same power, they were all benefitting from the draft of all the other riders in the pack.

I seem to remember some analysis somewhere about peloton riders in large TdF style races, World Tour riders & such...Anyway IIRC riders mid pack at 45kph were expending about the same energy as a normal person does while walking.

I guess cycling is different if the only resistance you need to overcome is rolling.

Anyway, Zwift is pretty smart & uses as much real world derived empirical models as the software designers & programmers could get their hands on.

Riveting

I wouldn't compare myself (solo riding) to the W/kg of those in the middle of that pack that flew by since Zwift has a drafting factor, like IRL. Maybe if you compared yourself to the leader of that pack, who was arguably putting out the most watts (assuming it was a flat section).

PeteHski

Zwift drafting is deliberately reduced relative to real life. They did this to make it (slightly) easier for breakaways to form. But it still makes a huge difference compared to riding solo. In non-competitive group event rides there is an option for the event creator to enable a feature called "double draft" which makes drafting more realistic.

But at the end of the day, physics is working against smaller guys when riding on flat terrain. You simply have to ride at a higher W/kg ratio to keep up with the bigger guys.

GhostRider62

I have been passed on the flats making 330 watts by another rider making 220 watts. This just does not happen in real life. If I keep my weight the same and make myself shorter in Zwift, I go a lot faster. They got some stuff backwards. Also the draft is nothing like in real life. But, it is just a game with 1990 style graphics.

PeteHski

Zwift group drafting is very tricky to implement because, unlike in real life, riders in the middle of a large group can go full gas whenever they feel like it because they are not restricted by the wheels they are following. So to prevent riders in a group blasting straight through the front row and accelerating the group to ever increasingly unrealistic speeds, Zwift came up with this "sticky" draft fudge where a faster rider gets temporarily pinned to a slower rider they are overtaking. This makes drafting feel very inconsistent. Sometimes you are bowling along effortlessly in a group and then for no apparent reason you are having to go full gas just to keep your speed and position. It's definitely not like real life, but it does keep you on your toes!

bblair

Yea, I get it. But wouldn't it be interesting to for the display to show actual watts output. I think I'd rather see that than W/Kg.

atwl77

This sort of power comparison comes frequently. A very simple rule of thumb (which also applies in real life), is that:

- when two riders are riding at the same power (W), the lighter one is faster
- when two riders are riding at the same W/kg, the heavier one is faster

Very easy to verify with any online bike calculator.

billridesbikes

I've noticed this stickyness factor and you have to plan for it. For example if you're in a group of riders and about to overtake a smaller group you have to boost your power a bit as your group overtakes so you don't get stuck on some wheel in the smaller slower group. Or I'll note who I'm following and try to continue to follow that rider through, although this doesn't always work. IRL this would never happen as the passing group would never barrel straight though a group of 4~5 riders.

billridesbikes

You can use the Zwift companion app to see the watts a nearby rider is doing. If they're doing a training plan you can 'look over their shoulder' and see their actual watts as they pass if you're using views 1,2 or 3.

GhostRider62

You should send that to the coders at Zwift.


Also, if one takes the same mass for a rider and makes them longer, their CdA is lower. Short and stocky is not more aero than tall and thin IRL, unlike in Zwift.

billridesbikes

This is unlikely to be true. Given the same mass the short stocky one will have less surface area and a lower CdA than a tall thin one. We can prove this with calculus to solve for a minimum area to enclose a volume, but as an example, take a sheet of paper and throw it. Now take the same sheet of paper and crumple it into a ball and throw it. Both have the same mass and volume of paper but which can you throw further?

PeteHski

Exactly!

It also affects movement within a large group. Sometimes you find yourself having to go full gas for no apparent reason whatsoever, with no change in group pace or gradient. Then you suddenly surge forward and have to back off to avoid riding off the front. It happens mostly in large groups rather than small groups of 4 or 5 riders. I haven't really thought much about the dynamics of it, but I expect it's caused by the power fluctuations of the rider you happen to be following. So if they suddenly back off the gas in the middle of a pack you probably get stuck to them and have to put out a load of extra power just to go through them and back on to the wheel of someone who is pushing.

What I've learned from this is not to ride near the back end of a large Zwift group as any riders dropping back through the bunch will make your life hard work having to plough through all their "stickiness". It's much better to get up to the front end of the group and then sit on the second or third row. I find this approach makes drafting more consistent and less overall effort to stay with a fast paced group. Life at the back is painful in those groups and I think this "sticky" dynamic makes it even harder for guys who are struggling to stay with the group anyway. They basically end up stuck to each other as they are losing pace from the group. It took me a while to work this out. I would often sit toward the back of a big group and wonder why I was having to make massive efforts every time I overtook a wheel in front who was slowing slightly.

GhostRider62

More frontal area loses the CdA battle all the time.

Drop a sphere vs an elongated spheroid of the same mass. The sphere will have a larger frontal area AND a higher Cd.

Ever notice that TTT riders are generally tall and thin. How many short and stocky TTT riders at the world class level are there



2 Minutes is a whole universe of difference......in the wrong direction

https://zwiftinsider.com/speed-tests-height/

GhostRider62

My Zwift race strategy is balls to the wall for 2-4 minutes off the line and then stay in the front half of the pack. This usually gets me a good placing. There have been weird times when I get shot out the back for reasons that escaped me and no matter how many watts I dialed in, I could not close a small gap. So, my bottomline is to do everything humanly possible to not get too far back in the pack, even if it means blowing up. Of course, this means I need a long warm up to be able to do such an effort off the line but I found I am dropped otherwise and no chance to place.

PeteHski

I would like to see both actually. Watts and W/kg in brackets. Then you get a better impression of the size of rider you are up against, since the 3 rider avatar sizes don't really give away that much.

GhostRider62

Both W and W/Kg display would be nice. When I was doing a TT at 40 km/h ar 320 watts and rider passes me at 44-45 km/h on 100 less watts, I was intrigued. Since it was a race, it was easy to look up her stats. Nobody does 44-45 km/h on 220 ish watts in real life. But, it is easy in Zwift if you are very short.

Over two minute differential on a 40 minute flat race between a short and tall rider of the same W/Kg (same wattage and same weight).

jpescatore

If you enroll in Zwiftpower, after any group ride or race you can see the detailed stats of yourself and any other riders in that ride or race who are on Zwiftpower (it is free.) You'll see max watts and W/kg, other info.

I love big rides like TdZ where you can ride at the pace you want to ride up and almost always join a group going at the pace or just slightly above/below. I don't really care about how many watts the others are putting out - just nice to be able to sit in draft and rack up more miles in a one hour ride at the pace I would have ridden solo with no draft. With distance rides (vs set time period), like TdZ, I try to latch on to a slightly faster group so that I'm doing close to the same power I was solo but going faster because of the draft.

billridesbikes

I myself have been working on my elongated spheroid shape during the pandemic though liberal use of beer. I expect to cut through the wind like a scythe though wheat this year.
TT riders also have freakishly long femurs and giant leg muscles. (see picture)

PeteHski

This guy just needs to work on his lower back flexibility

bblair

[QUOTE=jpescatore;22378221]If you enroll in Zwiftpower, after any group ride or race you can see the detailed stats of yourself and any other riders in that ride or race who are on Zwiftpower (it is free.) You'll see max watts and W/kg, other info.

Yea, I forgot about Zwiftpower. Cool site, lots of info there. I found myself quite a few pages down and can compare my power (not so great) with the other riders.

Thanks for the reminder.

unterhausen

Does zwiftpower have height?

esarhaddon

Yes. It is already visible on the specific race result pages. You do have to enable that column if you are looking at someone's profile to see what height they were for an event.

And yes. Zwift does seem to penalize people a bit on the flats for being tall compared to real life. If you want to ride a virtual race where the physics simulation seems to be closer to real life in terms of speed for power on the flats, try RGT.

Being 70kg and 170cm, I immediately notice a difference when I am trying to distance a large powerful rider on the flats switching back and forth between Zwift and RGT. On RGT I have to do relatively more w/kg to keep a gap.

Dfreeman617 

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