Miles per hour not matching watts and RPM's



   My miles per hour are not matching with the  watts and RPM’s I am putting out – are these results accurate?  All of a sudden my mph don’t seem to be matching up with my rpm and watt output – is this correct?  It happened quite a bit yesterday although I kept logging off and on and at one time just deleted and reinstalled the Zwift app.  

    In this screen shot my w/kg is 3.0 I am turning nearly 85 rpm’s and nearly 200w and still only at 13mph going up just a 2% grade (my trainer difficulty is set at 50%) – I feel I should be going faster and the ride up the 2% grade feels sluggish.  I am riding a Kinetic road machine Smart Control…the tire is inflated to 120 psi, I have re-calibrated on the Kinetic app (twice)…and the tension knob is correct, and again my trainer difficulty level is back to 50%.  

   It just seems inconsistent, this seems more realistic.  In this I am at 1.5/w/kg riding at 11 mph at 131 watts.  The top screen shot is after I got off the bike and re-logged on.

    Just as a comparison, in the first screen shot, my w/kg is 3.0 is 2 times higher, (than the screen shot below) watts are 63 points higher in the top screen shot , rpm’s are the same but mph is only 13 mph…so does this indicate some kind of an issue?  is there a tech issue, or is it me and I am missing something?  It just seems as if all of a sudden the ride got sluggish and my effort doesn’t equal what I am seeing on the iMac. 


  Just to test, I got back on, turned the trainer difficulty off – and did it again and it still doesn’t seem to match up.  My w/kg is 2.6 in this,  I am putting out 199w with 85 rpm’s and the speed up a small 3% grade is 13 mph.  I can’t figure it out – need help to see if this is right or not. 

How fast were you going when you hit the 2% incline?

It looks like you just started a ride so it does take a little bit to get up to speed. Do you see the same thing after about 5 minutes of riding on Zwift when you are up to speed?

that is a great question, I got back on the bike and it could be me, hitting the grades, am sending this your way.  6 minutes into the ride my mph is 23 my watts are 181with 95 rpm’s and a w/kg of 2.5
   I can’t get the other screen shot to load, but I hit a 1% grade, my watts go down to 149 my rpm’s are 86  my w/kg are 2.0 and my speed is 14 mph which I think feels realistic.   What do you think?

I would think that at 2.0 w/kg on a 1% incline you would be near 18mph, but that is just a brief snapshot in time. For me, if I average around 2.1 w/kg on the London flat course I can complete 20 miles in an hour. 

I am not sure how new you are to Zwift, but the following is used to calculate in game speed: In-game bike used, in-game drafting, weight entered, virtual elevation changes and watts (for zPower it’s your wheel speed and the power curve of the trainer selected converted to watts).

Speed over time is not as important as watt/power over time.

ok cool thanks, I am wondering if my FTP is set too high, just dropped it to 140 but it may I am now thinking after reading a bunch of articles should be lower than that – I am going to take the FTP test Wednesday, but is there a link between FTP score and Zwift difficulty – 60 years old, 5’9" 164 haven’t been riding that long (in fairly decent shape) maybe my FTP is set too high at 140.  What do you think. 

I would set it to 100 and suggest doing a free ride and having Zwift calculate your FTP. Do a 10 minute warm-up and then push yourself for 20 minutes and do a cool down when you complete and save the ride Zwift should recalculate your FTP if it’s higher then 100 (which I’m sure it will be). After doing this I would suggest dropping the FTP that Zwift calculated by about 10% before doing the real FTP test. 


  Thanks!  I will do that Wednesday, really appreciate it…pick a flat course I am assuming and will do a 10 minute warm up, push hard for 20 and then a 5 minute cool down…and will wait to see the Zwift re-calculation…and then I will drop it by 10%…that’s awesome thanks. 

That’s correct. If you were more experience in cycling I would just suggest leaving the FTP at what Zwift calculated, but dropping it 10% will help you get started.