New Pedals or Glute Issue? 15% FTP loss in 2 weeks

Hi Everyone,

I’ve been using trainerroad for the 2nd winter now, and I’ve run into issues. After a 2 week break at xmas, I did the ramp test and my Ftp dropped from 208 to 180. I repeated 1 week later and same result.

Ramp test history
Dec 13 - 208 3.2w/kg
Nov 22- 203 3.0w/kg
Sept 7 - 208 3.0w/kg

I was riding 4-5 times a week, polarized plan with approx avg TSS of 232 per week since Sept 1. At xmas, I received the Favero Assioma duo pedals to replace my spds. I ride the Stac Zero Powermeter trainer, not a smart trainer. The power readouts seem very close ±1% when used at same time. I also have a minor SI joint issue i’ve been dealing with for 4 months while training. My diet for 4 months has remained low carb.

What is the most likely cause of ftp drop? The new pedals seem to have a wider stance width than the spd’s.

Stats - 44yo Max recorded HR - 190

On Dec 13 ramp test, I did 5:45 of work above 170 bpm.
Last night Ramp test, I only managed 1min 33 sec of work above 170 bpm before I had to stop.

Can different pedals work different muscles to the point where I couldn’t raise HR any more before the weak link gave out?

Any other thoughts, with solutions greatly appreciated.


Two week break and moderate TSS prior seems like the result is likely. Also, take a look at your nutrition, cooling, etc. This doesn’t sound like a pedal issue to me but others will correct me, if I’m not as correct as I think.

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A full 2 weeks off the bike combined with a previously low TSS explains it. It’s not the pedals.

I usually drop around 8-10% of my FTP for a break that long. Don’t sweat it, it comes back.


I think this is likely the crux of the whole thing.

How diligent have you been about trainer resistance and tire pressure? Even the most consistent dumb trainer maintenance will see some variance - particularly when compared over time against a direct force power meter.

I’d suggest that the likely cause is that you’ve changed the source of your power measurement from a dumb trainer power curve to your new power meter pedals.

Tire pressure is irrelevant on the stac zero since the resistance is generated contact-free through eddy currents in your rim or break track (similar to brakes on roller coasters afaik). They claim the power meter gets its accuracy from knowing the strength of the currents but I don’t know the specifics. In any case, it tracks quite well with my vector 3 pedals.

That being said, if the wheel moves just a little bit between the magnets, the resistance becomes uneven and in my experience it’s quite difficult to exactly reproduce resistance between taking the bike on and off the trainer. Then again, I have never seen a 20w drop due to that.

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