I have two PowerTap G3 wheelsets. 1 Training and one with a ENVE 6.7 for racing. The training wheel stays on the road bike and the carbon wheel on the TT.
I have a suspicion that the hub on the carbon wheelset is reading slightly high (about 30-40 Watts). My reasons for thinking this are:
My RPE doesn’t match the power output shown.
2 Fairly comparable rides on the road bike and TT show same average power and NP but same average speed (the road bike is an old Trek 1.1 and the TT is a NP3) so surely the P3 would be faster?
When I run a ride on the P3 through BBS AeroAnalyser it comes out with a much higher CDA than the road bike.
Has anyone else had one of these slightly off? Googling it shows lots of people where it has been way off (either reading 50W or constantly over 500W).
I am in the UK so only service option is to send to Paligap for a service. I had thought about spending an afternoon doing some runs and swapping the wheels between bikes and then studying the data. Or should I just send it back for a service? My season has finished so I can live without the carbon wheel for a few weeks.
I caution against having someone other than PowerTap service your hub. PowerTap does an outstanding job at servicing the hub, has the parts and equipment to ensure the hub is calibrated correctly. Also, if you two day or overnight the wheel, they will match the shipping method when sending the wheel back to you and the wheel is serviced quicker. If you are in a hurry, they will work with you, to ensure your wheel is returned promptly, their customer service is that good.
Make sure that the trainer is warmed up during the testing of each wheel. The resistance of many trainers (such as those with fluid resistance units) goes down as it gets warmer, which would skew your results. Even the cooling in the time it takes to switch a wheel can affect it so get it warm again!
I have a normal wheel on trainer so will also try that.
Good point about getting both serviced. I have been assuming that the race one is off but it could easily be the other one!
Make sure you use the same or similar tire/tube. Different Crr would bias the results and testing on a small roller surface exaggerates the power difference for Crr. Tom A had mentioned that the difference in wattage between tire from this type of roller test is about a factor or 3 too high.
I have a normal wheel on trainer so will also try that.
Good point about getting both serviced. I have been assuming that the race one is off but it could easily be the other one!
Make sure you use the same or similar tire/tube. Different Crr would bias the results and testing on a small roller surface exaggerates the power difference for Crr. Tom A had mentioned that the difference in wattage between tire from this type of roller test is about a factor or 3 too high.
Damn that’s going to be a prob. The carbon wheels are tubs and narrow ones (long story I know wider is better, but the original rims were really narrow), the training wheels have wider clinchers on - butyl tubes.
The carbon wheels have 22mm 4000S IIs. I think I have another conti tyre in clincher which is 23mm. I can’t remember the model it came on my old TT bike (think its either a Grand Prix or Super Sport). Think that will be close enough?
My Garmin always prompts to zero offset when it pairs with the PM and I select yes every time. On the new firmware its 0 +/- 20 and both Hubs are showing normal figures.
Should have mentioned that in my original post. Kinda where my question came from. Both hubs seem to work but I have a suspicion one is slightly out, but I might be imagining it!
My Garmin always prompts to zero offset when it pairs with the PM and I select yes every time. On the new firmware its 0 +/- 20 and both Hubs are showing normal figures.
Should have mentioned that in my original post. Kinda where my question came from. Both hubs seem to work but I have a suspicion one is slightly out, but I might be imagining it!
I had a similar discussion/concern years ago with an older hub. For some reason I had a number in the acceptable range and the techs kept telling me nothing was wrong. I did the static torque test and came up with a 22% error. I had to pay for the service and when I did the same exact test when the hub was returned it tested very close to 2%.
As others have mentioned if in doubt do the torque test.
