Apologies for a Zwift newbie question, I’ve read some previous related questions but haven’t found a clear answer to this very simple question.
I use a Kickr Snap. When I’m riding in the same gear at the same cadence (I have a separate cadence sensor) I would expect my speed to remain constant, regardless of the incline.
But when the gradient changes, so goes from 0% to 2%, even if I keep the cadence and gear the same, my speed in Zwift goes down. On 5% inclines I virtually grind to a halt in the app even though I keep the cadence and gear the same by putting in more effort.
Why is Zwift changing my kph speed dependent on the gradient when my bike gearing and cadence stay the same? This is very different from reality, and prolongs the time it takes to get round a certain course distance artificially and incorrectly.
Edit: The solution appears to be to set the Trainer Resistance to 100% (from the default of 50%) in Settings.
Just keeping the cadence and gear the same does not equal the same speed on flat road and on climbs.
You might get closer if you increase the trainer difficulty to 100% but it is still a function of how the trainer simulate the resistance.
To go up an incline you have to produce more power (watt) than on a flat road, you can only produce more power by having more resistance if you keep cadence and gears the same. The best way to go faster up a clime is to change gears or increase cadence.
The Kickr Snap is a wheel-on trainer, so very sensitive to setup. Make sure you are carefully following the manufacturer’s instructions on tyre pressure and roller tension. And calibrate the trainer regularly.
If you start getting wheel slippage against the roller on inclines (as the resistance increases) then you will struggle to make progress on those inclines.
Check that Zwift isn’t showing your power going down as your speed goes down.
Because same cadence and gear in real life does yield the same speed, regardless of gradient, because cadence is just the number of times the wheel is going round and in the same gear that takes you the same distance on the road. There are many websites that shows speed as a function of gearing and cadence. There’s no mention of gradient being a contributing factor to speed (I can’t add a direct link to examples).
Yes I agree that I have to increase power to keep the cadence the same in any given gear up a hill, but in Zwift when I increase power so that I match the cadence I had on the flat, the app shows a much slower speed uphill compared to on the flat.
So say I’m pedalling at 90 rpm on the flat in any given gear and then I go up a 4% incline, I put more power in using the same gear to maintain the 90 rpm up the hill (which my cadence sensor tells me I’m doing) but Zwift tells me my speed is significantly less than when I’m on the flat in the same gear.
Sorry if I’m not grasping something fundamental about all this!
I think the biggest issue you might have here is the 50% trainer difficulty. This is, effectively, cutting the ‘feel’ of the climb in half when sent to your trainer. So, you may not be changing gear or cadence, but on a 5% grade you are then really only putting out the power of a 2.5% grade, meaning you would slow down (in game) because you need more power to maintain the same speed on a 5% grade.
I would suggest, then, that your start by putting the trainer difficulty up to 100% and see how things go at that setting. My guess is that it still won’t be ‘perfect’ (algorithms, calibration, etc.), but I’m guessing it should be much closer to what you are expecting.
Try setting your Trainer Difficulty to 100% and repeating your experiment
I think that what is happening here is because of your TD being at 50%. On a 4% gradient Zwift is giving you the resistance for a 2% gradient (because of the TD setting), but because it still requires the same overall power to get up the hill no matter the TD, it has to slow you down so you still produce the same overall amount of work.
When cycling on flat terrain the two main opposing forces are rolling resistance (energy loss between wheels and surface) and air resistance. Once you are pedaling uphill, gravity becomes the main resistance.
The OP is basically saying that when riding IRL if you maintain the same cadence in the same gear your speed should not change (power output yes, but not speed), but in Zwift this is not what they are seeing. TD of 0 would actually be the worst for this, since the same gear and cadence should result in just flat power output.
Not at all. The bike wheel is a fixed circumference, and in a constant gear the wheel will turn the same number of revolutions with each complete revolution of the crank (gear inches). Therefore, the bike will travel the same distance over the same period of time (same speed). As @Steve_Hammatt said, it will take more power to turn the same gear at the same cadence going uphill vs on the flat, but your speed would be the same.
Yeah that makes sense, however, I don’t think it is physically possible to do the same gear and cadence up a certain gradient, maybe beyond 2 or 3%. There will be a point to where you just don’t have the strength the go the same cadence in a large gear.