Tire wear on Dumb Trainer

Curious if others have had similar experiences, and hoping mine can spare someone confusion and frustration.

I’ve been using TR plans semi-consistently for about 8 months on a fluid trainer using virtual power (no power meter in the budget for me any time soon). After working my tail through training blocks, I kept seeing disappointing results on ftp tests. Modest gains and, in some cases, drops in ftp after very hard work. I felt super fit and strong on outdoor rides, so the situation baffled me, but I kept the faith and stayed consistent.

All this time I’ve been conscientious about chain lube and tire pressure, but I’ve been using an old road tire instead of a trainer tire. Well, recently I finally put a proper trainer tire on, and all of a sudden VO2 max felt like sweet spot, if that. I assessed, and my ftp jumped from about 235 to 300! Rolling resistance, man. About a 25% difference. Massive. Is it likely that the resistance was increasing throughout my training as my old tire wore out more and more? That would explain why my numbers were going backwards.

Of course it’s still just virtual power, so I don’t know what my REAL ftp is, but I’m choosing to believe it’s closer to this new one then the old one.

So yeah, trainer tire is worth it if you’re in a traditional trainer.

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Bicycle Rolling Resistance did a test of a brand new vs (really) worn Conti GP4000S II. The difference was about 1W.
New Vs Worn Road Bike Tire: GP4000S II.
Even the difference in rolling resistance between the best tire and the worst in the road category is about 15W. I think there must be something else going on with your virtual power, or your fitness really is changing around a lot.

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Interesting. Thanks for the intel. Must be something else going on, because I am certain my fitness didn’t jump 65 watts in a day after 8 months of fighting tooth and nail for every watt. Anyone have any theories. Truly all that changed was the trainer tire. The old one was extremely worn, and power aside, just pedaling in the easiest gear feels significantly easier now than with the old tire.

Which trainer and how do you set the compression between tyre and trainer? Is it automatic with a spring or do you have to dial it in? New tyre the same size as old one? Reason I ask is compression between tyre and trainer could be different.

Tacx have a calibration step in their app to get the correct tyre compression. I remember it being a surprisingly high force to get it in the green range.

After noticing my trainer tire being quite worn, I replaced it not too long ago. I enjoyed how much quieter and smoother it was at first, but not so much anymore as it gets broken in. My last FTP test wasn’t very good, so the new tire didn’t seem to help me.

Before I got a power meter, I relied on my Road Machine’s estimated power. That was a very bad idea and quite a faff to boot.

Set tire pressure, set spring tension, ten-minute warmup, spindown calibration, and after all that, power seemed to continue drifting, even within a workout. The spindown values seemed to vary widely between workouts as well. Not very confidence inspiring.

Now I just do a zero offset on my power meter before each session, which only takes a couple clicks, and off I go. I still try to maintain consistent tire pressure and roller spring tension, but that’s mostly for feel; it’s amazing how half a turn on the spring knob can effect how draggy the dead spots in the pedal stroke are.

I know power meters are expensive, but how do the dollars compare to months of hard work for watts that may or may not be kinda sorta accurate? And to answer your question, with a power meter, you could run whatever tire you wanted without worry over watts.

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I’m sure you’re right. Unfortunately I just need to make do with what I have for the time being.

It’s a TravelTrac Comp Fluid. Same tire size, and I always tighten the drum 1.5 turns after it touches the tire, as per the manufacturer’s recommendation.

I’m in the same boat guyarusso, re dumb trainer and not able to buy a power meter.
I did a power profile test recently which had stupid high numbers. It’s a shame for the ego but I just deleted the test.
Looking back the wheel may not have been tight enough or there could have been grease on the drum etc, allowing the tyre to spin more easily. Could this have been the case with your tyre? there may have been a waxy surface that has now worn off or similar?
With our limitations I just control what I can and train hard. As long as numbers are increasing it doesn’t really matter, no need to sweat it isn’t 100% accurate.

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