Turbo trainer spindown values

I’ve recently got an Elite Tuo wheel on smart trainer. I set it up and calibrated it with a spindown. I’ve since down several workouts with it and done a spindown at the end of each one so that it’s accurate for next time. I’ve done it after each workout as I figure the turbo will be settling in a bit so worth doing regularly to start with as it all loosens up etc. But everytime I do it I get a different value. Last night’s was about 17k whereas the previous one was about 16k. Does this make much difference in the grand scheme of things? What does the value actually represent? Does a bigger number mean the Sufferfest think my turbo is more resistant and so the workout is easier as a result?

Are you ensuring your tyre pressure (and the pressure from the roller contacting the wheel) is remaining the same? Could explain the changes.

EDIT: The value is the time in milliseconds (usually – can vary by manufacturer) that it takes for the wheel to stop after you stop pedalling (hence why you need to get it up to a certain speed first).

The value is the time in milliseconds

Which would also mean with a wheel on trainer your reactions could throw it completely as it hasn’t really anyway of knowing you stopped applying power when it says so

So if the tyre pressure is the same and I haven’t touched any of the dials that would change the pressure from the roller on the tyre then the readout should be the same? Is that right?

I believe the tyre pressure is the same and I’ve not touched the dials. Maybe the tyre pressure is lower meaning more drag and so more time to slow down. I was looking at getting a solid tyre for the turbo so maybe this is enough reason to do that.

Which would also mean with a wheel on trainer your reactions could throw it completely as it hasn’t really anyway of knowing you stopped applying power when it says so

It doesn’t need to.

You spin it up to “at least ……. mph”, lets say ….+1. Stop pedaling, and a few seconds later it’s exactly …..mph, it then times how long it takes to drop to some other figure*. It doesn’t need to react to you stopping, it just starts the clock when it reaches a certain speed on the way down.

I was looking at getting a solid tyre for the turbo so maybe this is enough reason to do that.

Turbo tyres aren’t solid, they’re just designed to work better once warm. Running old road tyres leaves a black stripe of rubber dust up the carpet. The bright orange conti trainer tyre still sheds some crap but nowhere near as much.

*I’d assume it’s not actually zero, you could get a much more accurate measurement by calculating the differential of the speed, which would give you the drag force at any speed.

Not sure doing at the end of a ride as prep for the next one is best idea. It can vary a bit with temp so thought generally advice is to warm up for 5-10mins to get up to temp and then calibrate.

In reality this is a massive faff so I never bother. There’s been a few times where things are obviously wrong and I’ve done calibration, but mostly I have just focussed on consistent tyre pressure and contact pressure-marking the dial to ensure it’s same each time.

marking the dial to ensure it’s same each time.

That’s a good idea. A tiny bit of tip-ex goes a long way.

Turbo tyres aren’t solid, they’re just designed to work better once warm.

Yes but something like this… THIS is solid so won’t reduce in pressure on the roller at all so one less thing to worry about.