Gear questions

Hello everyone,

I’ve been using Zwift since June this year with very little previous experience with riding, indoors or outdoors. My equipment is a pretty basic 24-gear MTB on a Tacx Flow Smart trainer.

Although in the beginning I avoided the largest chainring, with practice I came to the conclusion that the 30 & 39t chainrings are pretty useless for Zwift - I now use the 50t one exclusively. Also, for the vast majority of time I only use the three highest gears of the cassette (11t for flats, 13t & 15t for climbs) achieving a comfortable cadence (usually around 75).

I do not consider myself a strong cyclist (only been training for 5 months!) but I do feel that I could use an even higher gear. I don’t exactly spin out on flats but sometimes I wish for more resistance. I suspect I am doing something wrong but what?

For reference my FTP is 280w (3.2w/kg) and the trainer is always calibrated warm. Trainer difficulty is at 70%.

Any suggestions welcome! Thanks!

I haven’t riden the Flow Smart personally, but there should be a way to adjust the resistance of the trainer. I’m not sure that the Zwift game controls resistance in real time on this particular trainer to match inclines in the game.

But I’m guessing you should be able to use the Tacx app to set your baseline resistance, no?

The trainer has a twist-knob to adjust how hard the roller presses against the wheel. Using that and the Tacx app you calibrate the trainer.
There is no other adjustment possible, manual or through the app (that I know of at least).

Hi @George_Michalopoulos

At 75RPM with a MTB wheel in 50-11 you should be riding at about 40km/h.

there is currently no way to adjust the flat road resistance.

Things that you can do:
Increase size of your front chainrings.
change to a Road bike wheel, (worked on my MTB)

Increase your cadence. going to 90 RPM should get you close to 50km/h.

Also make sure your wheel is nice and tight against the trainer.

Make sure you pair the trainer as powersource and controllable.

Hi Gerrie,

I have never used the original MTB tire since it’s a 29" and wouldn’t fit the trainer. I replaced it with a Tacx trainer tire since the beginning and the speeds you’re mentioning seem about right.

I suspect increasing my cadence would be the right way forward, but also the most difficult! :slight_smile:
A bigger chainring could also be a good idea, I will look this up.

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Correct me if I am wrong, but increasing the trainer difficulty in Zwift will make your gears virtually larger. This would virtually lower your cadence at a set speed or increase your speed at a set cadence.

Yes but only on inclines and downhill, not on flat

I certainly think that starting by moving the difficulty slider closer to 100% would be a good place to start, but even at 70% I would think you’d be in a much smaller gear than a 50x13 or 50x15 going up the Alpe or the Radio Tower, or even some of the other climbs. If not, though, it might be time to start looking for a pro contract!

I’ve never seen a MTB with a 50T chainring.
9speed MTBs had 22/32/44 as standard,that changed with 10speed, they had 24/32/42.
29er MTBs normally have 22/30/40.

Ben you are indeed correct.
Just checked again and the crankset is a Shimano FC-M171 28-38-48Τ, thus the largest chainring is 48t, not 50t.

I did the Alpe the other day in 48x15 throughout, in just under an hour, and it felt just right (not easy, just the right gear!) I thought I would have needed lower gears as well but maybe I should have set trainer difficulty higher.

I think the issue might just be a combination of clueless rider, basic trainer (can only simulate up to 6% incline) and trainer difficulty not being at 100%. I will probably leave the chainrings alone for now and try increasing the latter - maybe I’ve got good excuse to get a better trainer if this doesn’t work? :wink:

Egan Bernal is still safe in his laurels…! :laughing::laughing::laughing:

I haven’t ridden the flow, but I did use the Kurt kinetic fluid trainer for a time.
It had an accurate documented power v speed curve, which programmes like trainer road or Zwift used to calculate power output. ( the faster you go the more friction from the fluid trainer)

In a workout you just had to change the gearing to give a wheel speed for the power ( and cadence) you needed to sustain.

just a +1 on this request / CX problem. with the Zwift crit announcement today (which is awesome BTW), the only way i’m going to have any fun is if Zwift allows me to put in my chainring size and then shift it to a virtual size that is larger to increase the resistence for all situations…

I ride a CX bike with 44 x 11/42 on my KICKR. IRL i have a 10/42 cassette on my wheels but like most KICKR owners, use the cheaper 11/42 (which doesn’t need an XD freewheel). I want to bump my chainring up to a 50 or 52 but my bike (3T exploro, max ring is a 44t).

I asked some other riders and what they do for Zwift racing is use the Wahoo app to manually set resistance or ERG mode. It’s not “cheating” but certainly loses the spirit of zwifitng IMHO.

Really just want to have a box that in the settings that says enter your chainring and enter your cassette range. I would put in 44T, 11T, 42T, respectively. Then Zwift would “recommend” virtually going up to a new chainring size.

I also think with mountain biking on zwift the reverse will happen. I am virtually mountain biking on my gravel bike and need a 34T ring. For roadies out there with a 2X setup this may not be as big of an issue on the chainring but the cassette range would be. (which Zwift ‘sort of’ already has covered by the “trainer difficulty” setting.


Same here. I have a training bike which is allowing me to sprint on the road as well as ride hard XC. But with my 11-42 casete and with bigger chainring 39 on the front I can make my trainer to generate more than 200W on flats with 100rpm cad! It makes sense for me to ride only on 3%+ incline. In ERG mode I can force the trainer to give me 500W+ on smaller ring (24) on the same casete. I am sourcing my power from stages so zwift shall be allowing to generate more power on flats with smaller chainring!