Tacx Training
I’ve had three different IC4 bikes now, all came calibrated differently and therefore had much different results on zwift. The closest bike was still 15% higher output than compared to power pedals. The furthest one off was 55% higher. Also, all of them exponentially were further off the more I increased the resistance.
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Christian - for the most accurate power match, did you calibrate 100 with the resistance knob turned just before the brake hits the wheel, or basically cranked all the way until it was unable to turn any further?
I am loving my Schwinn IC4. Works for the entire family, and solo training is perfect.
Yes, my FTP number is inflated compared to the only other reference I have (Precor Spinner Chrono Power at the local gym, which itself may have been overly generous). Before I try a second calibration, I’d like to understand what has produced the best results for others
By the way - the Schwinn power appears to track power pedals, but off by some scaling factor. See the charts posted by another rider
Hi Bill, I calibrated the bike just as described in the official calibration guide. So not cranked all the way but with a 1/4 turn backwards. Calibrating the bike helped a bit but the results are still way off and not at all comparable to other Zwitters. The more resistance, the more the results are off - kind of exponentially. I stopped using the bike as it is and I am now only using it equipped with my Garmin pedals. Just did Alpe du Zwift today and didn’t feel like cheating ;-).
Schwinn just got back to me after I explained the problem and sent my comparable results with the Garmin Vector 3. Schwinn is expecting a fix to be available mid-May 2020 - latest. The fix will either be available via USB stick or via exchange of the bike computer.
This is the original message from Schwinn in German:
In der Tat gibt es hier ein Problem. Die gute Nachricht ist dass wir bereits eine Lösung haben. Es wird eine neue Software geben welche das Problem beheben wird. Mitte Mai können wir diese voraussichtlich zur Verfügung stellen. Möglicherweise schon etwas früher.
Sie sind bei uns als Kunde hinterlegt und sozusagen in Backorder für die neue Software. Über den genauen Vorgang werden wir Sie rechtzeitig informieren. Bei einer neuen Software gibt es verschiedene Möglichkeiten. USB Sticks oder neue Displays. Aber wie gesagt, wir werden das rechtzeitig kommunizieren.
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Thank you so much, Sasha, for the info and great tips!
(And sorry for the late reply, only just now seen it.)
I just recently bought a Schwann ic4 . I am new to zwift and was thrilled with my performance. But I soon realized that there was something wrong. I am almost 70 years old. There is no way I should be able to beat all those 30 year olds. I will wait for a fix from Schwann but I don’t expect anything to happen until Covid 19 has settled down
I bought a Schwinn IC8 and soon realised the wattage readings were way off however I followed the recalibration instructions seen on one of the earlier posts and now is much closer to my expected levels. It is much more realistic but the only downside is I won’t be getting any KOM’s now and the Epic KOM took an extra 15 minutes to climb
Thx for the information. I hope we can publish it here so we can all know the solution.
Hi all… Can anyone recommend advice regarding the calibration of the ic8.
Here’s my issue.
Being a gross newbie, I’ve used up my 3 calibration attempts and it’s now reading the opposite way around on zwift, if that makes sense. Obviously I’ve done something major wrong. For example, set at 1 means I can’t move the pedals, set at 100, I’m freewheeling almost. I don’t know what to do? Of course, I can still use the bike, but with all the data the other way round is just a bit of a head f@ck… I’m hoping that one of you more experienced guys can help 
After seeing your message, I thought I’d try the FTP test and I got 312! Now I don’t have anything to compare this to since I have no one else who uses zwift, nor do I have a road bike.
My FTP ramp was 500w, and I’m the noobest with the bike.I did the whole test without much effor…and I hear on every tutorial that the test is very hard and you nearly die after it…
The values delivered by the Schwinn bike are more or less useless. It’s not even a linear offset which you could easily correct at least by “downsizing” your own results for the purpose of comparing different rides of yours. It seems to be some sort of exponential offset. That being said, it is very, very unlikely that you are actually having a 500W FTP - given that you are new to biking. I measured my FTP with 246W and just did the Catch Quest route with 1,700+ m altitude gain. I was really done after the 3:20h ride and averaged at a not so good 160W The at Home Cycling & Running Virtual Training App
If you are new to biking and in moderate/average shape, anything above 200W FTP can already be considered “good”. Just to put this into perspective. Given you are 1,80m and 75kg, your body would be able to produce 6,66 W/kg over one hour. Which is just about the power that Marco Pantani was able to produce during his career going up Alpe d’Huez ;-).
So, don’t trust these numbers and please don’t participate in any race on Zwift until Schwinn has fixed this. It’s just unfair. A quick, but expensive fix would be to buy and install power meter pedals, like Garmin Vector 3.
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You should contact Schwinn/Nautilus and ask them to get this fixed. It’s their fault that quite a lot of people need to play around with calibration and setting a calibration limit is complete bullshit imho. I would ask them to send a new bike computer unit or send over some USB stick override.
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Your FTP is more likely in the range of 124-175W than 312W.
Yes, I am fairly new to this as I’ve only been using an indoor bike properly since end of January, so I can imagine mine will be quite low. However, the test was a killer and according to zwift I burn almost 1000 calories. I don’t really pay attention to the console on the bike itself as I have noticed the only thing that usually matches on there is the rpm.
I would still not trust these numbers especially in the higher wattage ranges. The offset seems to be some sort of exponential. The only way to get some realistic numbers would be to install some power meter pedals. Until Schwinn gets this fixed mid-May.
Yes, I don’t participate in races. I just do trainings or circuits just to do exercise. So I don’t mind wattages or anything…but I’m angry with that…it would be great to have that information…
I’ve contacted nautilus…let’s see if we can get a bit more info (although some people did already and it’s supposed to be fixed in mid may…)
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Reading some of your numbers here, makes me think mine is DEF off then…while i am peddling my butt off and have always had decent legs on me… thinking my FTP is that high with my side and weight…maybe time to calibrate…I have my Pressure usually set around 30-34 lately last 3-4 races on my IC4 and am doing 70+ rpm.
Those stats look cool, is this through Zwift?
Do you find setting your resistance to 30 is sort of in the middle in terms of difficulty? Almost cruising?
Yup, all Zwift rides,
Originally when i started i was sitting in like 20-24 resistance range and was not easy, got me winded fast, now i try to start at 30, and stay there, i will for brief periods put it up to about 34ish and if i need to do a mad dash i just crank it to 40-50 until i am about to collapse, which is a few seconds…, but i usually have to go back down to around 30 and sometimes just below, so certainly not cruising, heart is pounding and legs are burning!
I am 6’4 and 210lbs as well…
I did find this site which puts my numbers around “fair” which kind of makes me think I may be okay and my bike not over the top…
https://www.cyclinganalytics.com/blog/2012/06/watts-kg-on-the-power-curve
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