1x MTB riders on trainers - lessons learned - intervals

Hi Zwifters,

This applies to Zwifting for interval training on a 1x MTB - might also be useful to some for road bikes.

Been experimenting with my 1x 29er on my Elite Suito for a few months. Frustrating without some lessons learned, especially when trying to ride intervals. Both my son and I struggled with this to the point of nearly giving up. We found two keys:

Lesson 1:

If your intervals are above about 350 watts, ensure your controllable trainer is paired using FE-C. Otherwise zwift can’t create resistance changes, and you will basically just have to make your own power - Zwift can’t tell your trainer to add resistance without FE-C control - may seem obvious to those who’ve already learned the lesson… but our pairings were all FE-C except for the controllable trainer (which was just ANT+) - and that doomed us until I tried FE-C. (This also explains why you don’t feel resistance changes on climbs).

If your trainer gets unpaired - be sure everyone knows how to repair (use FE-C).

If your intervals are below 350W, and you don’t want to feel gradient changes, then don’t use FE-C, or use the next lesson with FE-C (we just use FE-C all the time):

Lesson 2:

Before riding intervals, go to settings and slide the Trainer Difficulty slider all the way left (off). This will reduce the trainer torque changes dragging your legs to a stop.

How you begin each interval also matters - if you begin the interval (where power goes way up) at too low of a cadence, the torque change can drag your legs to a stop. Sometimes a downshift can help, but often it won’t… so begin the interval above 80 cadence and attack into it as you pass through the translucent wall - just like you’d begin a sprint - at the start point, go hard into the interval.

The greater your change of power from the rest to the interval, the harder you have to attack in order to counteract the torque change in the trainer - the trainer will apply the brake to ‘force’ you to ride at a set power - this is ‘Erg’ mode.

The companion app is very helpful for intervals - you can increase or decrease the power level by 10 percent using the ± keys on the companion app. If the torque drags you down, you can try reducing the interval rather than just abandoning it.

VO2 Max intervals are very difficult in Erg mode - because the intervals won’t follow your physiology - ie, a sprint at max that fades over time. You can try building a series of short intervals that ‘fade’ from high power to more naturally mimic reality.

If you build intervals using the slider, the minimum rest period is 30 seconds. We use 15 second rest periods for some blocks - which you can get by manually clicking on the rest period and typing into it.

Remember that your FTP matters - do the FTP test often enough to reflect your actual fitness – and remember that an FTP test is actually an interval - so it’s a workout!

Hope these help.

Cheers, d2g

Confused here. Are you saying that just Ant+ legacy would not control the trainer in ERG mode beyond 350W, like it is some upper limit or restriction? Or are you saying that ERG mode will not change resistance at all even down at say 100-250W?

Secondly you state resistance does not change on climbs. So does simulation mode (is that what its called) not work at all?

Lastly you mention 1X setup in the post title, how does that figure into this?


I am just saying I’m riding a 1x MTB on my trainer and struggled to get above 350W without the noted changes. Some of that relates to gear ratio as my biggest gear is 32x11 and my trainer wasn’t turning fast enough to generate higher watts - Other 1x MTB riders report similar issues of not being able to keep up to roadies or ride intervals as expected. My goal was to help narrow the problem set and be able to ride intervals at higher power levels.

My trainer didn’t change resistance via Zwift control without FE-C and I hadn’t noticed that when we repaired it some time ago that it wasn’t using FE-C. Several rides into things it seemed odd that the resistance didn’t change on climbs. The FE-C pairing was an important detail that despite my tech savvy nature I overlooked in my setup of 5 connections. My power, speed and cadence used FE-C by for some reason the controllable trainer was ANT+ in the pairing.

I don’t know yet but doubt that my settings will make me ‘faster’ on the flats - my gearing paired with the slider setting wont change that. So group rides and sprint speeds will still be subject to those limitations - meaning that the gearing limits initial sprint power maximums because you can’t accelerate the rear wheel to a high enough speed.

You should try different pairing modes on your trainer to verify what works for you.

Was just offering my experience - hopefully useful to others.

Cheers, d2g

Just to be clear:

If you’re riding a 1x MTB on your trainer, it’ll be difficult in normal Zwift rides to sustain above 350W due to the gearing (assuming a 32x11). On downhills I’ve seen up to 100Kmh, but on flats the speeds top out around roughly 45-50kmh which is difficult to maintain due to cadence in a 32x11 gear. My son can spike over 1000 watts but runs out of gear a couple seconds into the sprint. My jumps aren’t as high as his (oh to be young again) - and we both spin out the gears.

If you set up using controllable resistance (FE-C in my Elite Suito’s case), you can achieve intervals to the limits of the trainer - but the torque onset during the intervals can drag your cadence down to leg breaking limits… unless you attack into the interval and sustain a cadence above 80 rpm. Everyone’s fitness will determine their limits - we noticed the issue at intervals above 350 watts, particularly above 380. The slider setting seems to help reduce the torque onset issues.

Wish list:

Include an MTB mode for normal rides/races where the resistance curve gets a bit steeper on the flats and enable the watts to rise so that MTB riders can keep up to roadies - there should be an easy math model to allow for this - watts are watts that convert to virtual speed - as the incline rises, any corrections can fade out.