I bought a Zwift hub 3 months ago and am loving it but I run into a limitation, especially on races, of spinning out on flat sprints. I have a fairly standard 2x10 drivetrain on my bike. On flat sprints, doing 120 rpm, I’m only putting out about 500 watts and end up getting passed by guys doing 800 watts, which would require a very fast cadence for me. I’ve tried adjusting trainer difficulty settings but it hasn’t changed much because it doesn’t alter the resistance on flats. What can I do to tune up the resistance?
It sound like you have a Small grear ratio on the bike. what are your grear ratios.
Biggest front gear is 50 teeth and I have the default Zwift Hub cassette with 11 teeth I believe on the smallest gear, for a ratio of 4.55
I use a gravel bike with 42x11-40 on the trainer. No problems in all kind of courses becouse my confortable cadence is 90rpm. My PM is a Rotor Cranks so, in the sprints y control the resistence pressing the rear brake.
This is not a solution for your problem but maybe can helpe somene else who have a similar setup
David
Just looked at a couple of your most recent races and sprints on your CA ride activity.
I can see you generally hit 500-600 watts but on the ones I looked at Zwift is reporting that your cadence is around 80-90. Where are you seeing a cadence of 120?
I’ll do a regular ride and look closely; I’ll admit I have a hard time paying attention to the screen while sprinting and usually I start pedaling super fast before shifting and the delay in the display might be causing that. I didn’t know I could get cadence data retroactively. What do I do to find that?
Not sure where you look at your own ride activity but 2 options:
Companion App ride activity. If looking at the route map of the ride you have just ridden scroll the screen to the left. (Gives distance, time, heart rate, cadence, power and elevation)
Or
Sign into your Zwift.com account and look at your Activity Feed reports. ( same reports except speed instead of distance)
I’m not sure if your experience is normal or not for that gearing, since I don’t use it on the trainer, but you do have the option of using the QZ app (qzfitness.com) to configure virtual gearing and increase the trainer’s resistance if you want. Zwift does not have that feature built-in.
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So after a lot of experimenting on different grades, I can’t get past 600 watts, which may just be my strength right now, not my bike’s limits. Back to more training!
With that gearing outdoors, I can reach 900W on a moderate climb without using 50x11 or spinning 120rpm. If you really want to see your peak numbers, don’t rely on Zwift to show you - sync or copy your data to a third party app such as Strava, TrainingPeaks, Garmin Connect, intervals.icu, etc. Also review your Zwift peak power data on my.zwift.com to see what it recorded.
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The Zwift Hub is a wheel-off / direct-drive trainer. Pulling the rear brake lever would result in nothing with a rim-brake bike. At worst with a disc-brake bike, his brake caliper pistons would pop out onto the floor and brake fluid would leak everywhere.
Plus even if he were on a wheel-on trainer or rollers, it requires an upstream power meter.