@Gerrie_Delport I will do one today and save it for you to see
I am having a similar issue. I just bought a Saris smart trainer, have a speed sensor, selected the closest tire, and during my connection I can see my speed getting to 15 mph or more. So, seems fairly accurate based on how much effort I’m peddling. Then I got into Zwift, go into a ride, and suddenly, I’m going just 2 mph. I have noticed that if I am going up hill, I’m only going to go 2 mph. Then, going down hill, suddenly with the same effort I’m going 30+ mph. It’s just so unrealistic with the variances between going up hill and down hill. Is there any way to calibrate this so that I have a realistic ride? Or am I only supposed to ride flat courses because honestly, if this is how the rides are going to go, this isn’t a good experience.
Welcome to the Zwift forum
What smart trainer did you get? You should not need a speed sensor with a smart trainer.
Saris 1029T Fluid Trainer-Fluid Resistance, Smart Equipped
Think I misspoke perhaps. It came with a speed sensor that I had to attach to the inside of the wheel. And like I said before, when I connect it, it’s showing me riding at 15 mph with a typical pace. Then, when I go into a race, it’s so different.
Zwift takes the wheel speed broadcast by your speed sensor and the power curve (see below) of the trainer you select on the Pairing Screen and converts that to virtual watts, also known as “zPower”.
Your in-game speed is determined by those watts, the weight and height entered, in-game bike frame used, in-game drafting (Tri and TT bikes get no drafting boost), in-game wheel set, in-game road surface, and in-game virtual elevation changes.
Activating a Power Up such as the Truck (draft boost), Feather (weight reduction), or Helmet (aero boost) can further alter your in-game speed for a short duration.
For smart trainers and power meters:
Zwift takes the exact power/watts broadcast by your trainer, the weight and height entered, in-game bike frame used, in-game drafting (Tri and TT bikes get no drafting boost), in-game wheel set, in-game road surface, and in-game virtual elevation changes to determine your speed.
Activating a Power Up such as the Truck (draft boost), Feather (weight reduction), or Helmet (aero boost) can further alter your in-game speed for a short duration.
This is not a real trainer curve, only to demonstrate the concept.
Example: Your wheel turn at 40 km/h then Zwift will use the curve and determine your Power as 200w. Using a set of complex equations taking your weight, height, road incline , rolling resistance and other factors in to account Zwift will calculate your virtual Speed.
So that 200w can be 45km/h on a flat road or 12km/h on a hill.
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Thanks for all of that information. Very much appreciated. I’m noticing the biggest change in speed is based on elevation changes. I was riding a London course today as a test and it didn’t look like much of an incline. In fact, it wasn’t even noticeable but apparently it was a slight incline. My bike basically was going 2 mph. It was barely moving and everyone else is just flying right by me. That is “SO” unrealistic. Then when I finally start going down a hill, I’m then going 30+ mph. It’s this almost sudden stop going up a very slight incline that just makes the ride no fun at all. Now, if I was going up a very steep hill, I could see me going very slow. That I could understand, but a very small incline, I would expect to slow down just slightly compared to riding on a flat surface. My issue is the disparity is quite big. When I was riding the London course today, I just noticed that most of the ride I was barely moving and it just to a point where it was pointless to keep riding when my avatar wasn’t going anywhere.
Check your in game weight that you did not input your weight as ls but the games is in metric.
What gear did you use for the test, to generate the most power you need to be in your highest gear (big front small rear) and you need to spin the wheel as fast as possible.
Per the graph above faster wheel = more power.
My weight was set up as Imperial and I switched it to Metric and it automatically converted it. So, not sure that made a difference but I switched my weight and height to metrics. We’ll see if that makes any difference.
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What bike do you use and what gearing?
double check that you picked the correct trainer.
My trainer is not listed. I picked the Saris Fluid 2 as I have a Saris Fluid trainer but it’s not the Saris Fluid 2. I then also tried just a generic trainer as well. My bike is probably 25 years old. I’ve had it for a long, long time. My wheels aren’t on their list either. I looked up my tires and it shows 40-622 on the tire. I found a chart that showed these equate to 700 x 40c. That’s not listed on Zwift. So, I just chose the biggest number on Zwift.
I also rode a route in London today. We are expecting the exact same problem.
Can you post a screen shot of your ride.(your profile is private so we can not see the details) What gearing are you using at what cadence?
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Wow! your heart rate was all over the place, looks like lots of signal drops! Also, your cadence is super low, avg 34, is that accurate or is something not reading correctly from the cadence sensor?
Ok,
So you did 70w avr at 34 RPM
Depending on your gears and trainer this look about correct.
So the top yellow row is your big gear front and the left yellow is the gears on the back.
This is a cadence of 40RPM
Now if you look at the 42/12 gear you will see that is a wheel speed of about 17km/h.
Then scroll up to the Example curve you will see 17km/h is about 50w (your power curve may be different but this should give you the idea)
so if you want to go fast lets say 200w then you will have to pedal faster cadence (90RPM) in that same gear. That will give a wheel speed of about 40km/h and that will give 200w (looking at the example curve)
also.
There a lot of HR dropouts, try a new battery.
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@Gerrie_Delport thanks so much for the help.
Will do
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One thing I found when I was using a non-supported wheel on trainer is that going uphill I had to be in a low (or the lowest) gear, working the hardest and generating huge power numbers either in our out of my saddle, just to attain a corresponding speed that seemed closer to “normal.” Then, going downhill, I had to be in a higher than normal gear, spinning at a high-ish cadence, to get speeds at or over 30mph. More or less the opposite of how I would train outside (for Tris).