Last July I started training and racing with a Powertap SL 2.4 wireless. One hub on my training wheels, another hub on my Zipp 808 race wheels.
The Powertap was instrumental in helping me take a half-hour off my PB half-iron for a 4:50:00 in September - nothing special compared with lots of folks on the forum, but I’ve worked hard to integrate power metering into my training and racing, with good results. Naturally I plan to take the Zipps for my first Ironman with Power in New Zealand - departing in 4 weeks.
I pulled the Zipps out for a long ride last week, and found the power readings are funny.
The power reads too high compared with the training wheels and also my Tacx Fortius trainer.
I thought it was a problem with the zeroeing, but the Zipp PT hub reads zero watts at a standstill, then increasing watts as I coast faster and faster.
Coasting at 10 kph, I read about 20 watts.
Coasting at 30 kph, I read about 40 watts.
And so on - you get the picture.
I know I should re-zero so I show zero watts while coasting - but coasting at what speed?
I get a different result depending on the speed.
Any thoughts on the cause and possible solutions?
I live in Japan so it will be tough to send the Zipp to Saris and get it back in time for IM New Zealand.
Thanks
Chris