What is everyone’s strategy/thought process when deciding between their big chainring and small chainring for trainer rides?
In the past I’ve read of people using the big chainring to simulate fast, flat courses and the small chainring to train for climb-heavy races. I’ve since been using the small chainring for VO2 trainer rides and the big chainring for most everything else (sweet spot, endurance, threshold). On my latest VO2 ride, I found the first two intervals very difficult on the small chainring, so I switched to the big out of curiosity. It was surprisingly significantly easier. Had I done the whole workout on the big chainring I would’ve rated the workout ‘hard’ while the small chainring would’ve made the workout ‘very hard’ or ‘all out’ for me. Almost as if my ftp on each chainring would be very different. Has anyone noticed something like that in their training and how have you adjusted your training to address the weakness?
I’m not currently training for any particular race but I typically race half distance triathlons. As of now, just trying to improve overall power and wondering if I should incorporate more small chainring work to be more well rounded as a cyclist. Any thoughts would be much appreciated!
From context I am deducing you are using erg mode on your trainer. That means if you are in the big ring, the fly wheel will spin more quickly as each pedal revolution will lead to more flywheel revolutions. This is akin to what happens when you are on a flat piece of road and pedaling quickly: your wheels = flywheel will turn quickly, because you are going fast. You need to absorb more energy with a fast-turning (fly)wheel, which means your pedal stroke will tend to feel more even.
When you are in the small ring, your gear is smaller and it is more akin to climbing. Because your (fly)wheel is turning more slowly, maintaining a round pedal stroke becomes more important.
However, there is an important caveat: in erg mode your trainer will struggle more in the big ring, because smaller variations in cadence will lead to larger changes in wattage. So it’ll be harder for your trainer to hit power targets. That’s relevant for this bit of your post:
That’s because your trainer had a much harder time to lock on your power target in the big ring and most likely you were simply doing less power.
In any case, I’d advise against using erg mode for VO2max workout, especially for something like 30-30s where you have short bursts of power and the difference between on- and off-power is very large. Instead, switch to resistance mode.
I don’t use erg often, but when I do, I use a similar approach. I like the big ring endurance, and sweetspot and threshold. I find it feels smoother and more realistic, like riding outside. Small ring tends to work better for Vo2.
In ERG mode, my trainer can respond quicker and regulate resistance/power better if the flywheel isn’t spinning very fast. I can also change cadence more quickly. For that reason, I stick with the small ring and middle of the cassette (road gearing) for the most part. There are times I find shifting to the big ring (harder gear in general) can be helpful, like when transitioning from a seated typical cadence to standing at a lower cadence. I then usually shift back to the easier gear when going back to seated.
Another factor for me was noise, in my old flat I never got a complaint when I used the wee chainring and the once I used the big chainring, someone did complain!
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