Erg mode misbehaves, but only at the very start of the ride

The setup:-
I run a Bkool Pro smart trainer but the power measurements come from my Assioma power pedals. This eliminates the need to worry about any calibration on the Bkool and spin down nonsense.
The problem:-
At the start of EVERY ride, as I start to turn the pedals the power starts measuring and there is a low target power. Almost immediately I am on the correct power and ready to go. The issue is that I can feel the Turbo resistance biting and I have to push quite hard right at the start. (for a warm-up) It can take 1-2 minutes for it to sort itself out.
This only happens right at the start and for the rest of the ride, the speed of response is bang on. Even for a 5-second power surge, The software, pedals and Turbo are all working really responsively.
Below is an example ride. The start came under control quite quickly but I used this as you can see some 5-second surges and 30 rests that the work perfectly.

On the basis that TrainerRoad is getting the power from the pedals and then controlling the turbo, this seems likely to be a TR issue.

It’s not the end of the world and more an annoyance but I’m interested if anyone else has seen this or knows what might be going on.


This might be a result of the Bkool needing to warm up. At the start of the ride, the power and resistance load set readings may be more erratic, and when the TrainerRoad app is trying to set ERG mode levels based on the power readings from your Assioma pedals, the PowerMatch calculation is constantly re-adjusting and maybe setting a little too much resistance at the beginning of the ride until the discrepancy between the devices gets ironed out.

You may consider using the pedals and trainer without PowerMatch. This way, the trainer itself controls the ERG mode levels and resistance, but the power readings you see and are recorded come from the Assioma pedals. This will get rid of the constant power vs resistance calculation that PowerMatch does, which you can turn off in the settings of the Bkool paired in the TrainerRoad app.


Interestingly I tried switching off the PowerMatch and it seemed worse. Went really high and stayed there. You can see it here Log In to TrainerRoad The drop at 1:28 is me stopping to put PowerMatch back on. You can then see it drop to where it should be slowly.
It’s not a huge problem TBH. Just means I’m putting out a lot power with very cold legs. (they soon warm up)

Hmm, that’s strange. What gear combination are you using? The start of your Pettit ride looks like you’re experiencing a wattage floor.

Yup, I get this exact thing as well…though using 4iiii and Tacx Flow smart trainer. I’ve found that I can either keep going in the same gear and it takes a while for the power to come down, or I can pedal for a few seconds then shift a couple of gears easier which seems to trick it to hold the correct power.

It does seem very strange because I can be holding the correct power during the 3, 2, 1 countdown, then the trainer bumps it up when the workout begins (that to me would indicate it’s not a wattage floor issue).

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I wont be near my bike till tomorrow and will check but it’s a pretty low gear. Small ring at the front and 3 or 4th biggest cog at the back. Will let you know but, what is “wattage floor”?

Hmm, that might not be it then.

Sometimes when riding low-wattage intervals, riders may come into contact with what we call the “wattage floor” - essentially the trainer’s lower mechanical limit. When this happens, riders may not hit their target watts for recovery intervals since the target power is beneath the “wattage floor” of the trainer. In other words, the number of watts it takes to turn the pedals is higher than the target power.

When you come into contact with the wattage floor, it will often appear as though your trainer is “floating” above the target power. Each trainer is slightly different, but most commonly riders will encounter the wattage floor when riding recover intervals below 100 watts.

The good news is that the wattage floor is usually pretty easy to avoid. If you find that you’re running into the wattage floor, try shifting into an easier gear. The trainer’s wattage floor is lower when using easy gearing combinations, so down-shifting should allow you to reach those low power targets.

Ok, that makes sense. But as you say I don’t think that’s the issue as there is no problem in achieving low power during recovery intervals. Low power is my speciality :slight_smile:

At least I am not alone. :smile:

I’ll have to try the shifting gears. I’ve been getting the same and I think I’ve strained my left knee pushing through that initial resistance. It also interesting that you and @PSteely are experiencing it with a different set up from me, so its unlikely to be my set up. FWIW I am using an Elite Suito trainer and a Be Pro S power meter.

@PSteely did changing gears work for you?