Jet Black Victory

[Alex_Beebe (Alex)]

I take sticky to mean that there’s a bit more friction from the belt, especially before it gets worn into the groves on the pulleys and gets softer and more pliable. The softening part probably happens as the trainer (and belt) warm up.

The sweet spot for accuracy for my trainer seems to be when the trainer reports about 5-10 watts below my power meter numbers at the very beginning of a ride (first 3-4 minutes). Then as things warm and loosen, the two power numbers match much better. I wish there was a temperature compensation, but I think that just adds too much programming and probably increases the likelihood of failure or miscalibration.

As far as slippage, yeah there shouldn’t be any slipping at all. These same serpentine belt systems are used on heavy machinery (think air conditioning and power steering pumps in your car), and the tension from the retaining spring is very heavy.

ETA: Sticky might also be referring to the phantom watts as being similar to “sticky watts”, i.e., power reported even during coasting. Although, sticky watts in the Zwift context are an entirely different matter.

[Randy_Huggins (Randy)]

Thanks for pointing out the potential need for additional ventilation directed at the JBV for extended rides. I’ve never particularly noticed any differences between expected and actual resistance in my long rides, but it makes sense that heat would build up and have some kind of detrimental effect. I often end up doing an ‘involuntary’ spin-down calibration at the top of Climb Portal rides. LOL.

[_roadrash99]

Hi Steve, please tell me you found a solution because I’m facing the exact same issue right now, really throws me off when I hear the frame click when I put the power down.

[Alexandre_Poirier_Ib (Alexandre)]

Hi everyone,

I live in Québec, Canada, and I wanted to share my experience because I’m honestly getting quite discouraged with this trainer.

I bought my JetBlack trainer in October 2024, and right from the start I noticed a low-frequency vibration or humming sound on every pedal stroke — especially around 80–90 rpm and roughly 150 watts, for example on a 4% slope in Zwift. The vibration can be felt through the pedals, it’s audible, and it even travels through the floor (I live in an apartment). My setup sits on a very thick, heavy gym mat, so it’s definitely not a flooring issue.

I contacted JetBlack Canada support, who were very responsive and professional — they sent me a replacement unit right away. The new trainer even came with the new Zwift controllers.

Unfortunately… the exact same issue persists.
Same vibration, same humming, same intensity.

Here’s what I’ve tried so far:

Updated the firmware to version 4.23;

Rode for about 10 minutes on Zwift, then performed a calibration in the JetBlack app;

Tested with two different bikes;

Tried with and without the Zwift Click cassette;

Tested with and without cycling shoes, different thru-axles, and different floor types.
→ Same result every time.

Some extra technical details:

My Ultegra 11-speed chain has less than 300 km on it;

My first trainer was among the very first units shipped to Canada;

The replacement unit came with a rubber transport support and a mainboard version 3.11 (my first unit had 3.10);

The bearings are not identical between the two units, but the vibration remains exactly the same.

The Canadian JetBlack reseller told me it was almost impossible for two units to be defective in the same way.
But honestly, this trainer is unrideable — the vibration causes numbness, and it’s impossible to ignore since it happens on every pedal stroke.

Other than that, everything else works fine — the firmware 4.23 update, the connection, calibration, etc. But the mechanical issue persists.

My next step is to go to the store where I bought it and test another unit in person to see if it also vibrates at 80–90 rpm / ~150 W.

Also, does anyone know if it’s possible to find out when a JetBlack trainer was manufactured, maybe through the serial number or some other identifier? I still have both of my units at home, and I’m trying to figure out if my “new” one might actually be from an older production batch. It seems that JetBlack recently started including the Zwift Cog v2 with two controllers in all boxes, and some older boxes might just have a simple sticker added to indicate this — but I could be wrong.

It’s very frustrating: two trainers, same issue, and still no clear answer. I’ve read this entire discussion thread, and it seems like several others are experiencing similar symptoms. Hopefully, by comparing our cases, we can figure out whether this is a batch issue, a design flaw, or something else entirely.

Thanks in advance to anyone willing to share their feedback or testing results.