Gearing on DD smart trainer

I'm potentially in the market for a new TT, 20 years since i bought my last one. I'm looking at a direct drive smart trainer but considering the expense I'm not sure it's worth it, though I'll get use out of it.
Can anyone tell me how I'd use the gearing on the cassette, as my understanding is that the machine itself would change the resistance? I've used the cassette gearing on my current wheel on TT for years, so would a direct drive just be a mixture of both,or would I leave it in the same gear and rely on the machine?
I'd be grateful to someone could explain this stuff, as it'll help me to make my decision. Thanks!


  • Dorset_Boy
    Dorset_Boy Posts: 7,208
    edited November 2020
    Assuming you will be using the smart trainer with an app such as Zwift, Fulgaz etc then when the road goes up the resistance increases, just like out on the road, so you then need to change gear.

    If doing a workout, you can put the trainer in ERG mode. You won't feel the changes in the road gradient, but the trainer will control the resistance at a specific wattage, and so long as you maintain the cadence you won't need to change gear, even when the resistance changes to a different wattage.
  • slowmart
    slowmart Posts: 4,501
    What the boy from Dorset says. ERG sorts the resistance for you, either in watts or gradient. If you feel the need or use an external power meter to set your watts which means both your indoor and outside output will be using the same unit.

    If you don't have a power meter you may need to budget for an external cadence sensor as the one on the flux is inconsistent

    My LBS offers units for potential customers to try before they buy.

    That said there is a shortage of smart trainers due to lack down so you may not get your unit of first choice.

    Both the main manufacturers wahoo and Tacx have had their fair share of problems with units across the price spectrum but at least you have two years guarantee. Post guarantee there are some great online resources such as the facebook page for tacx owners of Neo (15,000 members) and the flux. Garmin support is pretty woeful in that it can take a while for a reply and I've heard wahoo has similar customer service but that's just hearsay.

    DC rainmaker on your tube has some great informed advice to the pros and cons of the majority of units.

    I've owned a smart trainer for a number of years, would i buy another one? I don't know. I managed to fix the last issue with the flux thanks to the advice from the facebook group although i still feel (IMHO) they have some product development to go before they are more resilient and less prone to failure. Add the customer service from Garmin and it lushes me towards a potential purchase of some rollers.
    “Give a man a fish and feed him for a day. Teach a man to fish and feed him for a lifetime. Teach a man to cycle and he will realize fishing is stupid and boring”

    Desmond Tutu
  • You can change the Trainer Difficulty setting on Zwift to OFF so that the resistance doesn't change when the road goes up. You still need to pedal harder to get up the gradient but it means you don't have to change gear
    'Hello to Jason Isaacs'
  • I don't have a "smart", trainer (using dumb trainer with PM pedals), but of you're working in ERG mode, I believe it is advisable to use your small chainring and middle-of-the-cassette gearing in order for you to maintain a more fluid cadence as the electronics sort the resistance out for you....