Schwinn IC4

I am using the IC4 primarily for zwift and absolutely love it. I’ve been riding hard for over 5 years but was missing any indoor training. I got a smart trainer last year but moving my racing bike indoors wasn’t working. My wife uses the bike for peloton also.

The IC4 pairs well with Zwift, pretty immediately, but it is showing me doing quite well on all my rides. I do push big gears and ride single speeds but still, I’m concerned that my fitness isn’t as good as it’s showing. It’s a spin bike so you’re always in motion, so when you get on a regular bike, you should be ready to go. That may also be the reason for high output, because you’re pushing high resistance on a constant basis?

I agree, I’m just a 49 year old guy who wants to stay in good shape. I’ll race but will be in the 50s class, power output is just a number.

I have the Schwinn™ IC4 / IC8 and Bowflex™ C6 Bike. My power readings are too high for my fitness level. I contacted Zwift and they said they couldn’t help me because the bike was unsupported. (As stated in post below only the Schwinn AC and the Cruiser are supported.) Zwift also instructed me to use speed and cadence outputs from the bike in the meantime. I do not believe this is possible with the IC4.

I’ve called Nautilus, the parent company twice. The first time I got nowhere. The rep did not understand what power was and said to contact Zwift. The second time I asked more specifically how to calibrate the resistance knob/console. I believe this is where the problem stems from. They sent me calibration instructions via email. He was walking me through them and I couldn’t get passed step 3. My rep then said the engineer he consulted said that might happen and that I got a bad console. So they are sending me out a new console under the warranty. However, I’m still not confident this will fix the problem, but I’m hopeful.

So if you are having power reading issues you may want to call and request the calibration instructions. I’ll try to screenshot the instruction here. I’ve seen elsewhere that the console algorithm for watts may be incorrect and they fixed it in later releases of the console. I’ll check back in later if this fixes the problem of high wattage readings in Zwift.


What weight Zwift thinks you are will make a difference. Check your body weight on Zwift.

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if the body weight has an impact on power output, can I enter a much heavier weight to neutralize the high output from the IC 4 bike?

Hey I just wanted to share my experiences with troubleshooting the bugs mentioned. Take a look here for my results.

Hope that helps.

Just thought I would post a message here to say:

  • I had experienced the same wattage inflation as others in using my (otherwise fine) Schwinn IC4.
  • Contacting the (excellent in many ways) Schwinn/Bowflex/Nautilus customer support and asking about the calibration process got me what seems to be the stock response: That the company engineers are aware of the problem and working with Zwift to determine a resolution, and that the fix might eventually be a fix in firmware or my console or some sort of adjustment at Zwift’s end. The customer support line, citing those engineers, specifically dismissed the potential for calibration as a fix.
  • Despite receiving that advice, I went ahead and went through the simple calibration process described upthread on this forum. (Essentially this involves turning your bike’s resistance adjustments to either end of the wheel’s range, and ‘marking’ something just shy of those spots for the console. Just be patient and retry the button combinations if you don’t see the right “Bottom range number is blinking” sorts of cues on the display. It took me a couple of tries to get there.)

So, after performing the calibration adjustment my wattage has, indeed, gone down to a range that seems much saner to me.

Whether my current performance is in any way “accurate” is another matter altogether, and I get that. In order to judge that we would need to use a separate measure — the $600 pedals. Here’s the thing for me: I’m not here to judge myself against others, or objective reality, anyway really. The numbers could be high for me on an empty course, and it wouldn’t bother me as long as I was measuring against myself. I just wanted to be “fair” in some way because of others’ experience and motivations, I think. My Zwift subscription is all about having the “game-i-fied” setting in which to push myself a bit, adding some fun structure (routes, workouts, intermittent reinforcement) and some good company. Thank you for those things, Zwift folks. It’s worth the subscription.

Anyway, if my goal was to not feel I was cheating others and return my measurements to something more like a reasonable range, the simple calibration process was worth it for me. It would still be great to have someone at either end of the Bike/app relationship address this, but this was a quick and dirty way to feel a little better and retain the essential fun and challenge of the thing. I’d do it again.


What the heck? I tried to do the calibration on my brand new, just came out of the box an hour ago, and the calibration count is already 3?

After the resistance shows 100%, the knob will turn another 2-3 complete turns before I feel any resistance in the knob, so it doesn’t seem like it is calibrated right at all!

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Just got my IC4 last week:
Very easy to link up to Zwift
Power reading as displayed by Zwift feels high
Speed reading is unrealistically high, even on the bike’s console (I am passing almost everybody in Zwift!! that can’t be correct)
Cadence reading is realistic

Will take my time and will run the calibration procedure, thank you so much for posting it! Will revert with results.

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I was having the same issue, then I did the calibration that’s explained on this page and it fixed it. I can’t understand why you can only calibrate it 3 times though.

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I would definitely call Schwinn and get a replacement computer. It’s possible it was a return or something or just a defect. But if you can’t calibrate it, it’s pretty useless. I calibrated mine and it made all the difference.

Has anyone figured out a way to translate the IC4’s resistance number to the elevation % in some way? FWIW I think mine is calibrated properly from the factory.

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I had the same problem that I was passing everybody on Zwift and I ran the calibration as described above and now my numbers make much more sense in terms of wattage and speed. Of course no idea how far I am from absolute precision, but definitely good enough to use Zwift.

Still potentially down the road thinking of buying a pedal-based power meter.

I did the same thing. I called customer support and was told I would need a replacement chip because there is evidently no way to perform a factory reset on the device. Absolutely ridiculous.

Well, that’s better than what I got from them which was just the sound of crickets.

So, for anyone who was successful in getting a replacement, what number did you call or how did you contact them?

‭(800) 605-3369‬

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I seem to be having the opposite problem of most. Harder I pedal more behind I get. It seems impossible to keep up with any group. Maxed HR and watts below 100.

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Here is what I have found based on my experience with Zwift using virtual power with HR and Speed and Cadence sensor and old trainer with bike, a road bike with power meter crank, then a road bike with direct drive Smart Trainer, and now a C6/IC4. Yes, the most accurate is an industry power meter. Yes, if you turn up the resistance high enough on the IC4 you will overstate power and likewise if the resistance is set too low your power will be understated on Zwift because it is translating power into a virtual number vs directly receiving the real number. The solution to be fair and as accurate as possible is to find a resistance "sweet spot "on your IC4 and leave it alone during races or rides. It will be easier at some points and harder in others but overall your heart rate and power should normalize over the ride to close to your actual power. However, if you decrease resistance at all from that setting to get relief you will lose too much power unfairly and likewise if you are in a sprint or hill situation and you turn up the resistance then power will spike unfairly on Zwift giving you an advantage over other riders. However, if you set your resistance in the 30-40 range and leave it there you will find you can be competitive and be able to compare efforts and progress over time. For example, last night during a race towards the final mile I increased my rpms to pass other riders and my HR increased to failure and I had to pull back the effort (not the resistance on my bike) and was dropped. However, if I had increased the resistance with a crank to the right on the knob I could have easily passed everyone with less effort. So my advice is to find that sweet spot and keep it there.


Great advice on how to deal with the issue. That is what I do myself.

I am looking to find riders with this bike and the c6 to do some Meetup rides together. If there is a group already people may be members of, let me know. Otherwise maybe we can start a group and do some group rides.


Please can you tell me which instructions did you follow? There are several manuals running and I’m a bit crazy.