Hi Nick,
I’ve been using Zwift with a classic “dumb” trainer with virtual power. It’s been a nice way to get my feet wet without spending a fortune. If you have your dumb trainer set up properly (proper tire pressure and resistance unit tension against your tire), it actually performs well in workouts and group rides. But as someone already mentioned, the power estimates are not considered accurate enough to allow you to place in the top three in races, so the most competitive people should opt for something more accurate. I’m planning to upgrade to something more accurate soon, but not in the direction of a smart trainer. Let me explain what I’ve reasoned to be the most suitable for me, and maybe others will agree…
As you already mentioned, the full potential of Zwift is realized when using a “resistance controlled” trainer, which adjusts the resistance you feel on the trainer to match the grade of the road. (Note that not all “smart” trainers are “resistance controlled” trainers. “Smart trainer” means that the trainer measures power and cadence, not necessarily that it can be controlled.) While resistance control might be a neat feature, and something I’d certainly like to try someday, I’m not sure that it enhances the experience all that much. Here’s why: When you hit a hill on a resistance controlled trainer, it gets harder to pedal, so most people shift down to get back to a cadence/power output that is manageable. If you don’t shift down, you either have to put out a bunch more power, or you cadence will drop to an inefficient level. In contrast, when you hit a hill with a dumb trainer, you don’t feel it so you can just stay at the same cadence/power output that is manageable—and you can always manually shift to harder and easier gears to vary the cadence/power profile of your ride. And to answer your question about blowing by people on hills by switching to an easy gear: remember it’s all based on the amount of power your putting to the pedals, not cadence. So you’ll notice that shifting to an easier gear and ramping up candence on the hills will oftentimes reduce your power output, and you’ll go slower. To launch up hills, you’ll actually find that shifting to a harder gear, and then trying to maintain a reasonable cadence (80-100 rpm) is most effective, but it’s hard! And it actually manually simulates what your peers on resistance controlled units are experiencing. Where you’ll find the biggest advantage to a “dumb” trainer is on the downhill—the resistance controlled trainers resistance drops so low that they have to shift to their hardest gear and they still struggle to put out any power. Meanwhile, you have plenty of resistance to push against, and you’ll be able to produce enough power to get flying down the hills.
My opinion is that the most important thing for a great Zwift experience is finding a setup that accurately measures power. Like I said before, the estimated power probably works okay if you have the bike set up properly on the “dumb trainer”, but nothing is as accurate as having a power-metered smart trainer or a physical power meter on the bike. Smart trainers (including the resistance controlled trainers) all measure power, but before I spend $400-600 on a cheap version of those, I think I’d rather get a power meter for my bike, because it’ll stay on my bike even when I’m not Zwifting. With a power meter, I can stick with my old dumb trainer, and I won’t have to use Zwift’s algorithms for power estimates—Zwift will read straight from the power meter.
So that’s my plan. I’m keeping my dumb trainer, and I just ordered Garmin Vector 3S pedals ($600) so that I can Zwift with some real power data that can stick with my bike, even when I ride outside (heaven forbid). Happy to update you on how the power meter pedals changes my Zwift experience once I unwrap them and install them on Christmas morning…
-Nick Adams