KICKR BIKE vibrations/resistance at high wattage and low cadence

Hey guys,

just got my KICKR bike today and, of course, took it for a quick spin on Zwift. Overall it is a great product, based on my first impression.

But I have one question… Let’s say I go at 300W and a cadence of around 100, the pedal strokes are very smooth.

But once the cadence drops at the same wattage, it feels like there is a huge vibration or a resistance that I have to overcome.

Is that normal or is it an issue that others don’t have? Kind of feels a little annoying.

Thanks

Daniel

Hi there,
I have Kickr bike as well. What you are describing seems similar to my experience. Trying to maintain 300w at a lower cadence is a challenge. I’d check trainer difficulty and make sure it isn’t ALL the way up, just to help mitigate the difficulty.
I’m sure you weren’t in ERG mode, but in case you were, that is def going to make 300 w at low cadence extremely hard.
As far as vibration, I can’t say I can relate to that symptom.
Would love to hear how it feels after a couple more rides.
Ride on!!!

Daniel, it would help if you clarify what cadence you drop to. On my Kickr Bike, if you ride in ERG mode at high power, it is critical to maintain high cadence. If the cadence drops, torque increases to the point at which it is very difficult to maintain it, and rotation of cranks becomes kind of jerky, you push very hard, it starts moving, as angular speed increases, resistance drops, but if you drop the pressure on the pedals for a split second, the resistance increases again. Is this what you are describing? My best known method is when I am on a workout in ERG mode and a high power interval is coming, I start spinning up the pedals some 10 seconds before the interval to make sure that I go into interval at at least 95 rpm, or over 100 rpm if interval power is really high, and I never allow RPMs to drop below 95 through that interval. The electromagnetic resistance system of KICKR Bike is very powerful and works instantly. There is no inertia to benefit from in the ERG mode. Power is torque times angular speed, if your angular speed drops, torque required to maintain the power becomes obscenely high.

You should not see any of this if you are not in ERG mode, no matter if it is a workout with ERG turned off, or a free ride. You power simply will drop as you drop the cadence.

Hello Andrei,

thanks for the quick reply. Let’s say I have a workout that is controlled with my Elemnt Bolt ( I am using the ERG mode here, so the KICKR BIKE automatically adapts the resistance or adjusts the watts), pedaling 300 watts at 105rpm feels very smooth and not jerky at all. Once I pedal those 300 watts and drop the cadence to 75rpm, rotation becomes, as you described it, very jerky.

Didn’t try a free ride yet, but I assume that going up a hill at 300 watts with a cadence of 70rpm, shouldn’t give me that jerky feeling then, if ERG mode is turned off.

Maybe I am getting this wrong, but I do need ERG mode if I want the KICKR Bike to be controlled by my Elemnt Bolt, right?

No, you will not get a jerky feeling at all when going up a hill at 300 watt at a cadence of 70 rpm (or 60 rpm, or 50 rpm) in a free ride! This is because Kickr Bike will not attempt to control your power output at exact 300 watts. Your power will fluctuate along the arc of the circle which your pedals travel. You might still be riding at an average power of 300 watts, but you instant power will fluctuate freely as it works for you.

Without ERG mode, if you drop angular speed of your pedals a little bit (think about it as instant cadence), your instant speed will drop slightly, and your resistance will also drop. You will easily recover to your target power in an instant.

In ERG mode, if your drop angular speed of your pedals a tiny bit, KICKR will automatically and instantly INCREASE the resistance to regain power, and this will likely force you to drop cadence even more, and so it goes in a vicious circle. At high cadence, resistance is not very high (even at 300 watt) and you can deal with these fluctuations easily, but as cadence get lower, you may find the limit where you start struggling.

I hope it makes sense. You do not need to even understand the physics and math behind it, just know that in ERG mode, at high power, you are not allowed to drop cadence.

If you start losing it at already 75 RPMs, then the target power is possibly too high for you - it may be suitable only for short intervals. Losing it at 65 rpms and below feels more normal…