Schwinn IC4/IC8 Power Figures


I have a Schwinn IC8 smart bike (but its not smart enough to deliver accurate power data to Zwift)! I have changed the console, which saw a reduction of 20-25% in the reported power data on Zwift. But I think it may still be too high. For info, my FTP assigned by Zwift is 329W. At 81kg, that gives me a power/weight ratio of 4. I’m reasonably fit, but not Cat A material. The bike cost a fair amount but I’m a bit reluctant to spend another £400-500 on power meter pedals without knowing how much improvement in accuracy they’ll deliver. So I was wondering if I could arrange a meet on Zwift with someone, and they lead off at a fixed power level, and cadence/resistance, the idea being I try to keep up with them so I can compare my bike’s power output against their’s. Would that work? Or are there too many variables to make it accurate enough? Would the other rider have to be a similar height/weight to me (174cm/81kg)?

Hoping someone can help.


This won’t address the issue. The issue is between the IC8 (I have the 4) monitors display resistance level and the actual magnetic resistance physically applied to the fly wheel. Your test would only confirm that you and the other rider are moving at the same speed and that the Zwift app has you both working at the same watts. This should be true on Zwift’s side regardless of the inaccuracy of your actual work.

I could be wrong on what I am about to assert so forgive me, but the issue appears to be the conversion of the 1-100 display multiplied by rpms to equate out a specific wattage. If your 1-100 calibration is off, the power output displayed is clearly going to be wrong. By calibrating your resistance you are attempting to fix the issue, but there is no way to tell if you have been accurate in your correction of the mechanical resistance.

This doesn’t take into account the power curve that could be different. the 1-100 resistance calculation could be a liner one where the actual power required might be closer to a curve. I have no idea how that would be corrected.

There was a post about the speed check you can perform. 50 rpm at 0 should equal 5mph (7kpm)
and 75 rpm at 25 (resistance) should equal 23 mph. This is from Nautilus.

I don’t know if that was just the MPH on the display or in the App.

Hi, thanks for your reply. I have now fitted a pair of Assiomo Uno pedals (single power meter on the left) to my IC8. I have seen my average power drop by about 100W, so am safely in cat D, pushing into C, instead of being in B and pushing into A! I have not recalibrated the bike - don’t see the need to if I have the Uno’s fitted.


That’s great. It’s a shame you needed to do that, but it is better than not knowing. Have fun.