Downhills and coasting on smart trainer

(Greg Clauson) #1

Hey all!  i am new to zwift, but after two days, i am fully addicted.  I do have a question though.  While on uphills, my Kickr fully adjusts for the incline as it should (i have the dial all the way to 100) but it seems on small downhills, i still need to pedal to accelerate (although its much faster as it should be) but shouldnt i coast down even a 1% grade?  In real life i would, but on there it seems i cannot coast at all on anything 1-2% as i would in real life. I mean, i am 255 pounds, so i get nice momentum haha.  

(Paul Graham) #2

Hi Greg

I would guess your speed on entering the decline will dictate if you coast and at what speed you coast. 

I use the Kickr and understand what you are saying but for me, coasting is relatively constant with what I would expect outside.

Have you been up and then down Watopia mountain to test your coasting?

I’m thinking you’ve probably done it, but the ‘spin-down’ calibration is important on the coasting stuff.

Ride on!

(Greg Clauson) #3

Hi Paul,


         Thanks for responding, i think you are probably right.  I am a pretty slow rider (14-15 MPH) so i am sure on the small little “hills” i have rode on, i wasnt fast enough to coast, even if in real life i would have, albeit slow.  I have done the spindown both on the wahoo app and the one on Zwift.  I will attempt the Watopia mountain, or at least some hill training or something so i can quit worrying about it.  Thanks sir!

(Nigel Doyle) #4

On Zwift if you coast on low gradient downhills without pedalling you’ll eventually stop. Say you want to finish your ride on Zwift and hop off your bike, if you carry on coasting until your rider hits a flat part you might be waiting a while for your rider to stop and the menu button pops up.

Personally I have the difficulty slider set at 40%. I race so want to be able to put put out power on downhills. Plus at 100% difficulty it makes the gradient resistance on my Hammer smart trainer harder than the same gradient outdoors.

(Macho Lim) #5

there’s no coasting on the kickr - u just have to ensure power is consistent and not too low for the software to think you’ve stopped.

The neo probably comes closest to having a coasting function - i understand it actually speeds up.

(Paul Graham) #6


What happens when you stop pedaling whilst going down a hill?


(Steve Copeland) #7

It’s trainer dependent. I have a Tacx Neo that not only coasts downhill it actually acelerates. Along with the road feel simulation it’s the nearest thing to actually being out on the road I have experienced. 

Linked with my Apple TV 4K it’s a pretty immersive experience. 

(Andrew Hare) #8

I use a BKool pro and I definitely notice the wattage decrease on a downhill section and speed increases even while spinning at a 20 Cad and 40 watts. But during a race I still will get dropped if you coast behind a group and that doesn’t happen in the real world.

(Greg Clauson) #9

Got it squared away. I just wasn’t on enough grade with momentum. I’ve since went down huge hills and def gain speed and can coast. Thanks all.

(Michael Coyne [CCCP]) #10

This seems like an issue that has been around in Zwift for a long time.  I can be on a slight down grade and stop pedaling, and quickly come to a stop.  Not on big slopes mind you, but on slight declines.  

The bike also decelerates way too fast on flat roads if a stop pedaling even for a second or two.  Once in a while on a ride … t’s nice to stop pedaling for a second or two and stretch.  Do this on Zwift and you’re stopped or dropped out of the draft almost instantly.  Not realistic at all.

Someone argued about this making an easy way to end a ride… Well, it would be just as easy to press a button to end the ride and keep the coasting realistic.

(Will Mosbey) #11

I am on a kickr snap and noticed this as well. My power seems pretty close and so long as I keep pedaling I’ll hang with the group but as soon as I take a quick breather on a down hill section or just to coast a bit to recover my rider will quickly slow down or come to a stop, as if the brakes were applied. This is a problem and does not represent actual riding. I’m curious to hear what the fix will be.

My difficulty is set to 50% and I have performed the spin-down successfully.

Anyone have suggestions?

(Steve Copeland) #12

It’s not an issue with Zwift, it’s the curse of wheel on trainers. The wheel needs to turn to provide input to the game to turn to movement. I have non of these problems on a Tacx Neo as the cassette actually accelerates downhill so you can take a breather as in real life. 

If you want greater realism you have to pay for it in the form of better kit not just expecting Zwift to come up with a fix. 

(Michael Coyne [CCCP]) #13


i agree that the NEO has a unique solution in that it will simulate downhill by motoring the wheel according to the downhill gradient and other factors.   However, I completely disagree about your assertion the wheel (or even cassette) needs to turn to provide input.

zwift uses a combination of inputs to determine progress, and wheel speed does not match distance traveled like in other simulations.   Rather, Zwift takes Power (or other surrogates for power) as an input.   So, if you stop pedaling on other trainers, the rate at which the spin down of the rear wheel ( or cassette on a KICKR ) occurs can itself be a surrogate for power.  So, stop pedaling and the power should simply be ZERO.  If the power is zero, then the simulation should take that as an input to determine REALISTIC coasting…

 not the crap we have now when the bike just stops on a -2% grade when the power goes to zero.   This is totally zwift’s fault, not the lack of having the best trainer.