Zipp Powertap Disc Wheel Test and Pumping Up

Today the Bay area was sunny, although it was a chilly 45 degrees this morning. After my Computrainer workout, I decided to finally take my fixed Zipp Powertap disc out for a test.
In case you didn’t know, pumping up a disc wheel is kind of a pain. You get this little L shaped adapter to put onto the tube valve, but it doesn’t grab on too well. If you have a friend nearby, it’s not too bad. But if you’re by yourself, it’s tough. At Ironman Florida, Ken Glah taught me his patented method of pumping up a disc wheel. Here it is:
(DISCLAIMER: I reshot these after I pumped up the tire; smart guys with good eyes will note that the lever to lock the pump head onto a valve is in the unlocked position. So follow the steps but lock the lever and you’re good to go!)
First you attach the L shaped adapter to the pump.

Note that the opening of the adapter points upward and the pump head and tube hang directly downward. This is so that the pump head and tube will not torque the valve on the tire’s tube, which makes it easier to hold it on. Otherwise, the pump head and tube will always drag on the adapter and want to pop off during pumping.
I use a Topeak JoeBlow pump which I consider the best damn pump out there. Its head has two holes for each type of valve (presta and schrader) on the same side; pumps with the holes on opposite sides really suck. I had one and it broke on me within a year.
Then I use my right hand to hold the pump head with adapter onto the tube valve, with the tube valve at its highest position and not near the ground:

Now the trick is to pump while holding the adapter onto the tire. I usually pump a little bit with my left hand to get the air started. However, there is no way I can get a decent force on it once the pressure builds. That’s when I shove it into my stomach area and press on it with my weight to get the rest of the air in, up to about 100 lbs.

You’d think that somebody would have figured out how to create a better way to pump up disc tires by now. Oh well.
Then I put on some warm clothes and go outside to test my Powertap. Supposedly they recalibrated it and I hope they did it right. When they sent it back to me, they sent it back to me in pieces: tire and tube off, cassette unmounted. Kind of lame. I just hope they fixed the Powertap problem of sending overly high wattage numbers.
Thankfully, after a chilling spin around the block, the PT was now reading correctly. No more 995 watt readings – sad but true, my day with Lance Armstrong quality power output were over.

Leave a Reply

Your email address will not be published. Required fields are marked *