i have an unusual /strange problem while using my kickr snap , my left crank keeps missing a beat or jumping slightly while peddling, its hard to explain !! , i have tried using another set of pedals , checking the cleats , also used another road bike , but the problem is still there , the bikes cranks are correctly fitted and tightened , is it possible the steel roller on my kickr snap has developed a warp , or bent with use ,
That does sound really weird. The crank rotation and rotation of the wheel are related by gear ratio. So, like many bicycle noises that are hard to troubleshoot, can you isolate the issue to a portion of the crank rotation or wheel rotation? Once you do that, can you then switch to different gears to see how it changes?
If you have this issue with the left crank “power phase” regardless of gear ratio then I start to focus on the cranks themselves or maybe how securely the bike is mounted in the trainer frame? The roller behavior doesn’t seem like it would be that perfectly synchronized to the crank across a variety of gears.
Is your left leg wildly stronger than the right and the force causes the tire to slip only on that side? I guess without fully understanding the problem it’s hard to guess 
Just my 2 cents…
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It happens at 11 oclock just as I put power on pedal. It occurs in different gears . My power is I guess about the same in each leg.
Also no tyre slippich.
Can you feel anything like a warp / bump when the wheel is just freewheeling on a spin down calibration? That could isolate it being the snap rather than the bike.
Might be worth trying an advance spin down too - (they hid the setting a bit but it’s still there (How to Do Advanced Spindown Calibration on Wahoo KICKR and SNAP - SMART Bike Trainers)
Won’t do any harm and I think from memory it does something with the brake calibration (it fixed my issue when my snap was reading wildly different power to my power meter)
I tryed a normal Spin down and tightened the roller more on the wheel . I am now getting more noise coming through the frame . I can’t see the advanced Spin down on Wahoo app.
The link I included has the instructions to do an advanced spin down but the important bit is :
“On the spin down screen, tap 5 times on the paragraph on top of the Perform Spindown button.
You should see “Perform Factory Spindown button. Tap that and follow the instructions.”
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Just went outside for a short spin … no sign of the issue so it must be the kickr snap with the problem. Can the steel roller be replaced. Or it’s a new trainer.
I found out how to do a factory spindown different to your suggestion. I had to go into wahoo utility. Pick my smart trainer on Bluetooth. Tap Bluetooth icon 10 times. And follow instructions.
I have noticed the steel roller seems to have warped slightly. But why would it affect the left crank.
The Snap has has some non-concentric (eccentric) issues with the rollers on some units.
How certain are you that it is strictly on the left side of your bike?
- I ask because it is practically impossible that the eccentric roller issue on the trainer will be restricted to one side of the bike.
- It will vary with each revolution of the roller, and it’s interaction with the rear wheel/tire. So it will cause issues on both sides and different points in the pedal circle.
Thanks for the comment. The issue is 99% left crank. I’ve tried different pedals and another bike with 3 types of pedals. Done a factory advanced Spin down but the problem is still there . Tryed a race today… and just waiting for that peddle jump each revolution is soo frustrating…
Honestly, given the amount of troubleshooting done on the trainer and the original problem statement…it doesn’t sound like a trainer issue to me.
The only thing I can think of is improper mounting onto the trainer or perhaps an unstable position for the trainer itself where when you balance your weight in a certain manner (this specific pedal position) it’s causing some sort of lack of tension
Neither makes a ton of sense, but that’s the only thing left in my head based on what you’ve already tried
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I’ve just ran upstairs to my setup. Shifted the position slightly. Re attached the bike to trainer. Took tension off the steel roller. I’m hearing a thud… thud … sound per revolution of the wheel. I didn’t have this week’s ago . . I’m pissed off. Probably time for a new trainer.
Is the thud consistent? Specifically, does it happen at the same point in relation to:
- The flywheel/roller on the trainer (put a small piece of tape on the flywheel to see exactly when it thumps).
- The rear wheel on the bike (pay attention to the valve stem location on the wheel when it thumps).
It should be timed to match one or the other, not both.
Well i decided to buy a new tacx flux s trainer. And even bought another second hand Bike . Also new cleats and new pedals… the problem is still there. Is it possible that all my 3 bikes have bottom bracket issues as there all a few years old. I’m really not dreaming this …
Well, you have effectively changed every variable (bikes, pedals and trainers) and the only thing that remains the same are you and the shoes?
Not sure what to suggest next?
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