Racing on Zwift using dumb trainer and PM - issues?

Was thinking of racing on Zwift using a dumb, wheel on trainer and PM but was worried that peak power might be too low due to issues with the wheel on drum style of dumb trainer I have.

For TTs I imagine it's fine, also should be OK for breakaways but wondering how limiting it might be for sprints. Does anyone do what I'm trying to do and have any other issues I should be aware of?

I really don't want to splash out on a new PM only to discover I cant do this well as I would like to win or at least contest races.

Thanks
Sometimes you're the hammer, sometimes you're the nail

strava profile

Comments

  • bobmcstuff
    bobmcstuff Posts: 11,196
    If you have a powermeter, you won't have any issues with low power on Zwift - Zwift will take your power from the power meter and convert that into a speed on Zwift (using its physics model).

    If using a dumb trainer with no PM (using virtual power - Zwift has a library of dumb trainers where they have got the power curve), then yes, you will experience some issues particularly around peak power/sprints as the wheelspeed on the drum will lag behind your input somewhat.

    There's also inherent inaccuracy in the method, as it uses wheelspeed on the trainer to estimate power from a speed:power graph, and with a wheel-on trainer there are lots of things that can affect how the wheel rolls (tyre, pressure, temperature etc.). I did use virtual power on trainerroad for several years, and it was generally fine, but you have to take care to keep the setup pretty constant.
  • I've certainly tried it in the past with problems exactly as you describe - with wheel on I had slip when sprinting etc but the rest of it was completely fine. I've now bought a direct drive smart trainer though, for ERG mode and realistic ride feel on the hills. That's what I found more of a drag to be honest.
  • thistle_
    thistle_ Posts: 7,148

    I've certainly tried it in the past with problems exactly as you describe - with wheel on I had slip when sprinting etc but the rest of it was completely fine. I've now bought a direct drive smart trainer though, for ERG mode and realistic ride feel on the hills. That's what I found more of a drag to be honest.

    +1
    I didn't really do mega sprints in events but I struggled with wheel slip on a lot of the workouts where you had to suddenly put down a lot of power very quickly. Having said that I could get the power up quite high if I ramped it up over 3-4 seconds.
  • rj2013
    rj2013 Posts: 21
    I moved from a wheel on trainer with Garmin PM pedals to a smart, direct drive one over lockdown 1.0. I didn't particularly have many sprinting issues, yes the wheel may slip a little when you really sprint hard but it didn't make an appreciable difference, you just need to get the resistance at the right level on the trainer.
    The biggest issue I had was one of simply keeping up, without a smart trainer I found I couldn't push up the hills as hard and didn't seem to get enough of a break on the flats and downhill to recover. A smart trainer has massively increased my enjoyment.

    long story short, you'll probably be ok, lots of other people use zwift this way but, if you are gonna splash cash then maybe look to do so on a direct drive smart trainer (i still use my PM pedals on my smart trainer rather than the inbuilt power meter but that's more a matter of preference.)
  • There's also inherent inaccuracy in the method, as it uses wheelspeed on the trainer to estimate power from a speed:power graph, and with a wheel-on trainer there are lots of things that can affect how the wheel rolls (tyre, pressure, temperature etc.). I did use virtual power on trainerroad for several years, and it was generally fine, but you have to take care to keep the setup pretty constant.

    Indeed. Zwift also places a 400W limit on these types of setups .. hence me looking into upgrading my setup.
    Sometimes you're the hammer, sometimes you're the nail

    strava profile
  • Thanks for all the feedback - appreciate the time taken to answer and it's great to hear what people have actually experienced. It does sound like a smart trainer is the way to go if, ultimately, I'm going to spend hours and hours on zwift. Just the minor details of finding the cash and, of course, an actual trainer in stock.
    Sometimes you're the hammer, sometimes you're the nail

    strava profile
  • I've used a dumb trainer and a PM a few times while somewhere that it's not been easy to plug in a smart trainer.

    It's OK, obviously if you want to sprint and put out larger power, you'd need to ramp up the resistance either through changing gear or using the manual resistance. It's doable, but you won't get the full experience.

    If you are going to use the PM while outside on the same bike, using PM power gives you a consistent measure, while the power from a trainer will be slightly different.
  • If you are going to use the PM while outside on the same bike, using PM power gives you a consistent measure, while the power from a trainer will be slightly different.

    Absolutely. But I've come to the conclusion that after many years using a PM for training (got through two sets of pedal based PMs by wearing them out) that a PM is only useful if it actually changes your behaviour .. and for me, it currently wouldn't. I now go with a simple polarised approach to training (aim for two hard sessions a week and the rest easy rides) .. and I don't really strictly need a PM for that. For sure a PM is also really useful for tracking fitness changes but even then I'm not going to change my training behaviour on my bike. This might change in the future, I may get back into TTs and perhaps doing FTP tests outdoors\checking aero positions but right now I don't need one. Also I prefer to race on real bikes and not zwift but I might be convinced to race on zwift during the winter if the setup is right (as I've get older the desire to race outdoor winter series has definitely faded) .. but even then I'm only really looking at zwift because I can no longer race in a velodrome.
    Sometimes you're the hammer, sometimes you're the nail

    strava profile
  • kingstongraham
    kingstongraham Posts: 26,231
    edited November 2020
    Outside I find it more useful in moderating effort while on long climbs than keeping efforts high on intervals. But I'm not a racer, just like the numbers.
  • bobmcstuff
    bobmcstuff Posts: 11,196
    I'm only a racer on Zwift :wink:
  • pblakeney
    pblakeney Posts: 25,750
    Just make sure that you weigh 55kgs.
    The above may be fact, or fiction, I may be serious, I may be jesting.
    I am not sure. You have no chance.
    Veronese68 wrote:
    PB is the most sensible person on here.
  • rj2013
    rj2013 Posts: 21

    There's also inherent inaccuracy in the method, as it uses wheelspeed on the trainer to estimate power from a speed:power graph, and with a wheel-on trainer there are lots of things that can affect how the wheel rolls (tyre, pressure, temperature etc.). I did use virtual power on trainerroad for several years, and it was generally fine, but you have to take care to keep the setup pretty constant.

    Indeed. Zwift also places a 400W limit on these types of setups .. hence me looking into upgrading my setup.
    I am sure you know this but dont forget if you have a PM then there is no 400W limit as you are not using Zwiftpower. you just wont experience the gradient changes, generally speaking you'd struggle a little uphills to keep up and be dropping everyone downhills to a certain extent.

    on the Trainer front, I picked mine up over lockdown from the Wiggle Ebay shop. they come up reasonably regularly and if you are careful they can be decent value. always worth keeping an eye on!
    https://www.ebay.co.uk/sch/tri-sport_resort/m.html?
  • bobmcstuff
    bobmcstuff Posts: 11,196
    edited November 2020
    For racing I am not actually sure a dumb trainer and PM would be much worse, provided you can use your gears effectively.

    I usually set the gradient effect on mine down to around 30% for racing, which is a pretty common tactic (default is 50%, so a 10% gradient Zwift tells your trainer to simulate a 5% gradient - because many cheaper trainers max out at 8 or 10%).

    Means you don't spin out as much on descents, and most critically for me is it means I only need to use 5 or 6 gears on the cassette in the big ring - my turbo bike is incredibly badly set up, the top and bottom of the block are basically inaccessible...

    https://zwiftinsider.com/best-trainer-difficulty-setting/

    It may seem odd, but many Zwift racers turn Trainer Difficulty up for flat races, and down for climbing races. Why? Because they want the gearing flexibility of low Trainer Difficulty on long climbs, while high Trainer Difficulty lets them “feel” slight changes in gradient on flat routes such as Fuego Flats.

    High Trainer Difficulty on flat routes makes even more sense if you’re racing a time trial, because it lets you feel those false flats and apply a bit more power to keep your speed high. Without having your Trainer Difficulty set high on a flat route, you may be on a slight incline and not even notice the difference – until you realize your speed has dropped by 2kph!


    I don’t have access to the stats, but my guess is the majority of Zwift racers run their Trainer Difficulty below 50% when racing. Why? Because it keep their effort more even, reduces the need to shift gears, and ensures they won’t run out of gears on descents.