Does weight slow you down - on Zwift?

(Thomas Vainio-Mattila) #1

Last night in Richmond - I was on 30km/h speeds until the twin hills, then my speed slowed down dramatically and everyone fly pass me (its not that bad in real life…) I udenrstand that you have to increase power going uphill, which I do, but still my speed going uphill seems much slower than in real life? Anyone else having this issue?

I am 180cm/95kg and using Elite Qubo Fluid trainer.

(Michael Meysarosh) #2

From what I understand about Zwift, it would certainly make difference as Zwift speed principal revolves around a W/Kg and that would implicate the combination of your power and weight accounted in the formula. So on the flats, your main opponent is the wind but uphills you need a certain amount of power to raise your total potential energy. Which in general rings true in the real world as big sprinters are often unable to keep up with small men at the professional level.

When you’re climbing, you should be going up at a similar speed to those who are producing a similar W/Kg. If you weight 30% more than a person going up along side you, an additional 30% more power will be needed to climb at a similar rate. This is why in cycling, the wattage is a number to note, but the watts per kilogram is the more indicative figure to gauge comparative levels of performance.

In the real world, we also need to understand that people have wide range of bike fits and flexibility. This will affect the flat and downhill speeds greatly and is difficult to simulate in the game.

(John Murphy) #3

To add on to what Michael said, the steeper the gradient the more weight has an an affect.  It’s hard to compare outdoor climbs to Zwift unless the gradients are the same throughout, in addition to all the other variables of course (wind, air pressure, drivetrain efficiency).

Conversely, if they modeled it correctly (and I’m guessing they did) then increased weight will help on the downhills, albeit probably less so.

It’d be interesting if someone tests different weights on Zwift with the same power output, heck I might give it a go.



(Tom Boden) #4

FWIW.  I am also a big guy and I see similar speed drops, not using a smart trainer.  In the real world it takes a pretty big and long hill for me to drop to 3mph and I drop to 3mph almost immediately on every hill in Zwift, even running at 17mph approaching the hill.  I have to put out way more power in Zwift on hills than in real life. That being said, I went out and bought a smart trainer to, hopefully, provide a better real-life experience. 

That being said, I don’t know the grade (%) of the hills around my house, which I feel are comparable.  And all I have are hills to get home, very little flat around my house. 

(Michael Meysarosh) #5

Some of the grades on Island hit around 11%, which is likely where you drop the speed. Now when your out in the real world and you reach a hill, you gearing changes (and thus the torquing forces) and tendency for most to increase power output keeps you going at a greater momentum (something that fluid trainer cant’ emulate). On a fluid trainer, it stays rather a static load so its far from an actual ascent. The fluid trainer is great for simulating a relatively flat road at a high rate of speeds, but not much else. If you do increase your output, you still would get a great workout, but nothing like going uphill.

I’ll likely invest in a smart trainer as well in the future, but I’m currently more targeted to achieve certain fitness goals first and the fluid trainer will start out fine for that. But if your already at good level and you want to get specific training to help take on an event with lots of climbing, the smart trainer will most certainly be the way to go to prepare.

(Tom Boden) #6

Michael, believe me I understand the physics of it. The problem I see on the hills is certainly partially related to the trainer, but it is every hill on Zwift, the same (almost exact) drop in speed occurs.  My wife and I were going to ride together once and she sped away from me and I could not catch her, that doesn’t happen in real life.  

I am certainly not knocking Zwift, I think it is awesome, but I think we need some adjustability to make it feel/act more like we would see in the real world, especially since that is kind of the point.  


I I don’t have the answer, unfortunately.  But I am hoping the smart trainers get us a lot closer  

As a side note, using my Tacx fortius I could climb 9-11% hills at about 6-7 mph, but I had the resistance driving to push harder. I don’t think the fluid trainer generates enough resistance to push me that hard and I don’t force myself to do it. 



(Michael Meysarosh) #7

How is the power being calculated?

(John Watson) #8

I have the same problem at 110kg / 203cm. Tried just getting power from the KICKR and now able using my powertap p1s for outdoor consistency. Zwift makes me much slower than other riders and I just can’t wait till they make a NYC course so I can prove it to them with real data. 

(james Schofield) #9

i am a heavier rider at 104 kilos, i was riding box hill last night and seemed to be going 6kph, this was at around 6%, on a hill like this in the real world i ride at around 12-16kph…

my wattage seemed lower on the hills too

apart from trying the two spindowns… would “trainer difficulty” make any difference?